Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[Nicolas Cadieux]

Hi Garth,

Good point.  I expect this has more to do with the satellite constellation at 
the time of the measurement than anything else.  Some reading I have been doing 
suggest Glonass as being slightly less accurate.  This could be caused by 
atomic clock precision, or less accurate broadcasting of ephemeris. This could 
be checked in post processing with a proper GPS.   As I see it, Glonass is Most 
important when you don’t have enough GPS satellites in view like when working 
up north or in some settings when satellite are hidden from view (mountain, 
buildings...).  I don’t think a gps like the eTrex will improve Much if you go 
from 8 to 16 satellites If the first 8 are well positioned in the sky.

Planning ahead of time to know where and when to measure is always the best 
practice as I see it.

Nicolas Cadieux
Ça va bien aller!

> Le 2 juin 2020 à 13:56, Garth Fletcher  a écrit :
> 
> A QGIS reader pointed me to a Sep 2019 US Forest Service report,
> ,
> which compares the accuracy of various GPS instruments.
> 
> Their Garmin eTrex 30 section stated that the eTrex's accuracy was ~ 3X
> poorer when using GPS+GLONASS instead of GPS-only mode.  This seemed
> rather counter-intuitive.
> 
> I checked using my eTrex 20 by taking 38 measurements distributed over
> an 8 hour period at a precisely known location, half using GPS only and
> half using GPS+GLONASS modes. Canopy type probably "Light-Medium".
> 
> The results indicate that GPS+GLONASS does increase the accuracy, albeit
> only by a modest amount.  It  most certainly does not decrease it!
> 
> A plot of my results on a 1 meter grid, along with descriptive
> statistics, can be downloaded (69 KB) from:
> 
> 
> Cordially,
> -- 
> Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[Garth Fletcher]

A QGIS reader pointed me to a Sep 2019 US Forest Service report,
,
which compares the accuracy of various GPS instruments.

Their Garmin eTrex 30 section stated that the eTrex's accuracy was ~ 3X
poorer when using GPS+GLONASS instead of GPS-only mode.  This seemed
rather counter-intuitive.

I checked using my eTrex 20 by taking 38 measurements distributed over
an 8 hour period at a precisely known location, half using GPS only and
half using GPS+GLONASS modes. Canopy type probably "Light-Medium".

The results indicate that GPS+GLONASS does increase the accuracy, albeit
only by a modest amount.  It  most certainly does not decrease it!

A plot of my results on a 1 meter grid, along with descriptive
statistics, can be downloaded (69 KB) from:


Cordially,
--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[Garth Fletcher]

Thanks for that very intriguing info, which I had missed.

For others interested the link mentioned is found in
Qgis-user Digest, Vol 171, Issue 50
 Message: 5
 From: Randal Hale 
 where Randy provides this link:


Which provides important comparisons by model and by canopy ("open",
"light-medium" and "heavy-closed").

The website is searchable by manufacturer/model, or you can download
the entire 750 test results in PDF or XLS format.
Very valuable comparisons.

At first I was confused by the "Position" column in both PDF and XLS
formats, until the website clarified this to being the number of
positions that were averaged together.

There is also a useful "NSSDA Standards" link.

Looking specifically at the Bad Elf GNSS Surveyor:
it is interesting to note the relatively small improvement when going
from single measurement to 60 averaged measurements.  This confirms my
belief that the errors are not primarily random noise, which should
decrease almost 8 fold when 60 measurements are averaged. This is
consistent with my observation that the reported locations "wander"
slowly as the satellite geometry changes, i.e., are not random noise.

Looking at the Garmin eTrex 30 information:
Again there is negligible improvement from averaging.
The use of GLONASS does very significantly decrease the accuracy
(increases the errors), independent of whether WAAS is used.
The latter is quite surprising, very counter-intuitive, and very
intriguing!

As recommended I will compare some measurements with and without
GLONASS enabled.

On 5/31/20 3:44 PM, qgis-u...@stripfamily.net wrote:

On 5/31/2020 1:20 PM, Garth Fletcher wrote:

The eTrex was receiving both US GPS and Russian
GLONASS satellites, plus WAAS (as indicated by a "D" in the Garmin's
satellite signal bars).


earlier in this (very interesting) thread a pointer was provided to a 
speadsheet that contained the results of the USFS tests of a wide range 
of GPS units. One thing that was surprising was that for a number of 
devices, including the eTrex30, the accuracy /decreased/ when GLONASS 
was enabled in addition to GPS. You might want to repeat this experiment 
without GLONASS to see if you experience the same effect.


--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[qgis-user]

  
  
On 5/31/2020 1:20 PM, Garth Fletcher wrote:
The
  eTrex was receiving both US GPS and Russian
  
  GLONASS satellites, plus WAAS (as indicated by a "D" in the
  Garmin's
  
  satellite signal bars).
  


earlier in this (very interesting) thread a pointer was provided to
a speadsheet that contained the results of the USFS tests of a wide
range of GPS units. One thing that was surprising was that for a
number of devices, including the eTrex30, the accuracy decreased
when GLONASS was enabled in addition to GPS. You might want to
repeat this experiment without GLONASS to see if you experience the
same effect.
  

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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[Garth Fletcher]

I have added some data to my earlier report, both from my Garmin eTrex
and from a Bad Elf Surveyor.

As described earlier I established an accurately measured test location
(± 2.4 cm) and taken 17 readings with my Garmin eTrex 20, distributed
over a 10 hour period. The eTrex was receiving both US GPS and Russian
GLONASS satellites, plus WAAS (as indicated by a "D" in the Garmin's
satellite signal bars).

These points were plotted on a 1 meter grid with a link provided in my
earlier report to the PDF graph.

That graph
    (56 KB).
has now been updated with more Garmin eTrex 20 data plus some data using
a Bad Elf Surveyor. On the updated graph the original 17 points are
plotted as blue unlabeled dots.


I added another 12 pairs from the Garmin eTrex, taken at the same
location at variable intervals throughout a 10 hour period on May 27. The
first reading in each pair was taken (Mark Waypoint) and stored,
followed by a second reading in which I told the Garmin to "average
waypoint" before storing. This averaging takes from 4 to 10 minutes
until a bar reaches "100% confidence", whatever that means.
Note that this is not Garmin's recommended use - which is to average
waypoints with at least 90 minutes between.  However my immediate
averaging should filter out short term "noise".

These points are plotted as green (immediate) and red (averaged) dots,
labeled x and xA, e.g., 1 and 1A, for the immediate and averaged points,
respectively.  I also added thin magenta lines linking the two dots in
each pair.

That data indicates a ±7 meter "wander", even in the averaged data.


I also set a Bad Elf Surveyor at the same location and recorded data
over a 2 hour period into a RINEX file. The estimated position returned
by CSRS-PPP post processing (Rapid) is plotted as a yellow star. CSRS
also reported a distressingly large error ellipse: 10.8 x 8.7 meters!

While the Surveyor is recording via its Bad Elf app one can also display
a "Deviation Plot" which shows the wandering of the measured location,
centered over its recent average (past 15 minutes).  This "wander" was
observed to drift slowly within a 20' (6m) radius circle; i.e., in any
15 minute period the maximum drift seen was ±20' (up to 40'), but could
have been larger over longer intervals.

While the Surveyor is described as being compatible with US GPS and
Russian GLONASS, it can use only one constellation at a time.
Consequently the Surveyor tracks many fewer satellites than the eTrex
which tracks both GPS and GLONASS.  This further reduces its performance
in less than the optimal "360° open sky" environments.

The Surveyor, like the eTrex, is also a single-frequency receiver, thus
its RINEX recordings cannot be post-processed by USGS OPUS.  CSRS-PPP
will process single-frequency data (includingg GPS + GLONASS), but is
constrained by the limitations of single-frequency data and wandering
data.


My conclusions:
under realistic field conditions (not all satellites visible) neither
  the Garmin eTrex nor the Bad Elf Surveyor can be relied upon for
  mapping-grade accuracy.
the Surveyor's RINEX capability is of very limited use due to its
  single constellation and single-frequency limitations.
the slow "wander" in single-frequency GPS location suggests that
  averaging, even if done with several widely spaced observations, is
  unlikely to improve accuracy.  It would be necessary to average many
  dozens of readings evenly distributed throughout a satellite orbital
  period (~12 hours) in order to get a reasonable sampling capable of
  reducing uncertainty.
--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[Priv.-Doz. Dr. Maria Shinoto]

 like a laptop or a tablet.  No 
>>> screens or anywhere fancy.
>>> 
>>> https://geneq.com/land-surveying-geomatics/fr/fabricant/sxblue
>>> 
>>> Nicolas Cadieux
>>> Ça va bien aller!
>>> 
>>>> Le 27 mai 2020 à 11:19, QGIS.USER  a écrit :
>>>> 
>>>> Hi Garth,
>>>>   Thank you for the correction and the additional information. Much 
>>>> appreciated.
>>>> 
>>>> My current thinking is that in the archaeology we do, the intra-site 
>>>> (relative) measurements are quite good but what is inaccurate is the 
>>>> absolute measurements. We can set out our grids with cm accuracy but can 
>>>> only locate them on the ground with 10s of metre accuracy. It would be 
>>>> good to have a low cost way of establishing the absolute position even if 
>>>> that took time and/or was off-line.
>>>> 
>>>> Ray Carpenter,
>>>> Chapel Archaeology
>>>> 
>>>> -Original Message-
>>>> From: Garth Fletcher [mailto:ga...@jacqcad.com] 
>>>> Sent: 27 May 2020 15:25
>>>> To: QGIS.USER; qgis-user@lists.osgeo.org
>>>> Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a 
>>>> cell phone
>>>> 
>>>> Hi Ray,
>>>> 
>>>> Apologies for the typo - I had typed iGS3, but iG3s is the right number.
>>>> 
>>>> iGage 
>>>> <https://smex-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=www.igage.com=068947a3-968f-435b-8f88-0b9b8eb439a9=276d51547942e21b974d48c8cd7101aa75dd6e1a-f9ccd777f828c1b394629f942585917bb0a34506>
>>>>  iG3s, now replaced by the iG4 which adds Galileo
>>>> tracking but otherwise seems very similar to the iG3s. $2400 US.
>>>> 
>>>> These track satellites from the US GPS, Russian GLONASS, Chinese BeiDou
>>>> and, with the iG4, European Galileo constellations.
>>>> 
>>>> Their sole function is to record from all the satellites they can track.
>>>> 
>>>> They produce a RINEX format file which can be sent to a post processing
>>>> service such as Canada's Geodetic Surveys' CSRS-PPP:
>>>> <https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php?locale=en>
>>>> 
>>>> The longer the observation (recording) duration, the better CSRS-PPP can
>>>> converge to an accurate location.  In my experience in New Hampshire's
>>>> heavily wooded environment, a 30 to 45 minute observation time generally
>>>> gets me to better than ± 1 meter accuracy.  Yesterday a 6 hour long
>>>> observation in a small field surrounded by forest converged to within 1
>>>> inch.  Dense forest canopy reduces the number of satellites that can be
>>>> tracked. Also, some times of day are better than others in terms of the
>>>> number of satellites and their geometry, see:
>>>>  <https://www.gnssplanning.com/#/charts>
>>>> 
>>>> The iG3s was perfect for my specific conditions, but I think it is not
>>>> optimal where many locations within a site must be accurately me
>>> ___
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> 
> 
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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[j . huber]

Hi Maria,

the position of the base station at the entrance of the valley sounds
good. Before you invest a lot of money, you could rent a system and try
it out in the field. Most local dealers should have devices available
for rent or tests.

The problem with wet conditions could have to do with multipathing
effects. Probably a choke ring antenna will be better in these
conditions. You could try an experiment: Put your GPS in a flat box
which is covered with some conductive material (eg aluminium foil) so
that it only "sees" signals from above (the visible sky), not from below
or the lower sides. See if this changes the resulting accuracy.

Using a GPS antenna mounted on a pole has the advantage that your body
does not obstruct parts of the visible sky. When measuring near a steep
slope, be sure to stand on the side of the slope where the GPS can't
"see" the sky anyway. I know surveyors who use very long poles (like
3-4m) to position the antenna above the lower layer of vegetation. You
get errors due to the lack of verticality but much better reception.

You can't expect to get cm accuracy in the conditions you describe, at
least not with short-time measurements. For this you need phase tracking
which is very sensitive even to short obstructions of a satellite signal
(canopy).

Unfortunately it sound like you don't have sight contact on ground level
either, so a GPS base station as a reference and a total station for
measuring the individual points won't be an option.

Regards
Jochen



Am 28.05.20 um 01:53 schrieb Priv.-Doz. Dr. Maria Shinoto:
> Hi fellow archaeologists ;-), 
>
> there is so much precious information in this thread. 
>
> Now one question about precision and accuracy: As I said, we work in a 
> densely forested area, there is not just the canopy of the trees, but two to 
> three levels below with dense ground cover and bamboo walls. Still, we get 
> excellent (precise) results with consumer level handhelds and smartphones. 
> But the accuracy is not good under certain conditions: Water and muddy ground 
> seems to be an obstacle for GPS as well as the steep slopes. We get very 
> precise results in certain places, but they are in certain cases several 
> meters apart from the "real" place -- which we can test with the LiDAR DTM. 
> Dry underground and measurement about 10m apart from the slopes result in 
> accurate positions, but any measurement point closer to the slopes leads to a 
> consistent error in the measurement -- across devices. 
>
> I still wonder whether these conditions are suitable for any GPS technology 
> or whether working with a fixed station and a rover would be OK. I could then 
> think of positioning the station at the entrance of the valley and walking up 
> narrowing valley with the rover.
>
> Best, 
> Maria
>
>
>> Am 28.05.2020 um 02:17 schrieb Nicolas Cadieux 
>> :
>>
>> Hi Garth,
>>
>> I am also an archaeologist.  We use a single Sxblue 2 from GENEQ.  The unit 
>> was upgraded by the company so it’s takes in the Russian constellation now.  
>> The unit is very precise. When we go out on the field, we let le unit run 
>> one a Bench mark for a few hours.  We then process that position  In PPP or 
>> using nrcan gps tower if we are close to one.  The company give a really 
>> good service helping with both software support and hardware.  As everything 
>> in made and designed in Québec, they can take the unit appart and change 
>> individual parts and chips.  We did that one as the Bluetooth chip was now 
>> longer capable of working with Windows 10 (more likely the other way 
>> around). It had been Made for Windows 95.  For a few extra bucks, they 
>> changed the gps chip also.  The unit is basically a brick (Square and heavy) 
>> that connects to an external device like a laptop or a tablet.  No screens 
>> or anywhere fancy.
>>
>> https://geneq.com/land-surveying-geomatics/fr/fabricant/sxblue
>>
>> Nicolas Cadieux
>> Ça va bien aller!
>>
>>> Le 27 mai 2020 à 11:19, QGIS.USER  a écrit :
>>>
>>> Hi Garth,
>>>Thank you for the correction and the additional information. Much 
>>> appreciated.
>>>
>>> My current thinking is that in the archaeology we do, the intra-site 
>>> (relative) measurements are quite good but what is inaccurate is the 
>>> absolute measurements. We can set out our grids with cm accuracy but can 
>>> only locate them on the ground with 10s of metre accuracy. It would be good 
>>> to have a low cost way of establishing the absolute position even if that 
>>> took time and/or was off-line.
>>>
>>> Ray Carpenter,
>>> Chapel Archaeology
>>>
>>> -

Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[Priv.-Doz. Dr. Maria Shinoto]

Hi fellow archaeologists ;-), 

there is so much precious information in this thread. 

Now one question about precision and accuracy: As I said, we work in a densely 
forested area, there is not just the canopy of the trees, but two to three 
levels below with dense ground cover and bamboo walls. Still, we get excellent 
(precise) results with consumer level handhelds and smartphones. But the 
accuracy is not good under certain conditions: Water and muddy ground seems to 
be an obstacle for GPS as well as the steep slopes. We get very precise results 
in certain places, but they are in certain cases several meters apart from the 
"real" place -- which we can test with the LiDAR DTM. Dry underground and 
measurement about 10m apart from the slopes result in accurate positions, but 
any measurement point closer to the slopes leads to a consistent error in the 
measurement -- across devices. 

I still wonder whether these conditions are suitable for any GPS technology or 
whether working with a fixed station and a rover would be OK. I could then 
think of positioning the station at the entrance of the valley and walking up 
narrowing valley with the rover.

Best, 
Maria


> Am 28.05.2020 um 02:17 schrieb Nicolas Cadieux :
> 
> Hi Garth,
> 
> I am also an archaeologist.  We use a single Sxblue 2 from GENEQ.  The unit 
> was upgraded by the company so it’s takes in the Russian constellation now.  
> The unit is very precise. When we go out on the field, we let le unit run one 
> a Bench mark for a few hours.  We then process that position  In PPP or using 
> nrcan gps tower if we are close to one.  The company give a really good 
> service helping with both software support and hardware.  As everything in 
> made and designed in Québec, they can take the unit appart and change 
> individual parts and chips.  We did that one as the Bluetooth chip was now 
> longer capable of working with Windows 10 (more likely the other way around). 
> It had been Made for Windows 95.  For a few extra bucks, they changed the gps 
> chip also.  The unit is basically a brick (Square and heavy) that connects to 
> an external device like a laptop or a tablet.  No screens or anywhere fancy.
> 
> https://geneq.com/land-surveying-geomatics/fr/fabricant/sxblue
> 
> Nicolas Cadieux
> Ça va bien aller!
> 
>> Le 27 mai 2020 à 11:19, QGIS.USER  a écrit :
>> 
>> Hi Garth,
>>Thank you for the correction and the additional information. Much 
>> appreciated.
>> 
>> My current thinking is that in the archaeology we do, the intra-site 
>> (relative) measurements are quite good but what is inaccurate is the 
>> absolute measurements. We can set out our grids with cm accuracy but can 
>> only locate them on the ground with 10s of metre accuracy. It would be good 
>> to have a low cost way of establishing the absolute position even if that 
>> took time and/or was off-line.
>> 
>> Ray Carpenter,
>> Chapel Archaeology
>> 
>> -Original Message-
>> From: Garth Fletcher [mailto:ga...@jacqcad.com] 
>> Sent: 27 May 2020 15:25
>> To: QGIS.USER; qgis-user@lists.osgeo.org
>> Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a 
>> cell phone
>> 
>> Hi Ray,
>> 
>> Apologies for the typo - I had typed iGS3, but iG3s is the right number.
>> 
>> iGage 
>> <https://smex-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=www.igage.com=068947a3-968f-435b-8f88-0b9b8eb439a9=276d51547942e21b974d48c8cd7101aa75dd6e1a-f9ccd777f828c1b394629f942585917bb0a34506>
>>  iG3s, now replaced by the iG4 which adds Galileo
>> tracking but otherwise seems very similar to the iG3s. $2400 US.
>> 
>> These track satellites from the US GPS, Russian GLONASS, Chinese BeiDou
>> and, with the iG4, European Galileo constellations.
>> 
>> Their sole function is to record from all the satellites they can track.
>> 
>> They produce a RINEX format file which can be sent to a post processing
>> service such as Canada's Geodetic Surveys' CSRS-PPP:
>> <https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php?locale=en>
>> 
>> The longer the observation (recording) duration, the better CSRS-PPP can
>> converge to an accurate location.  In my experience in New Hampshire's
>> heavily wooded environment, a 30 to 45 minute observation time generally
>> gets me to better than ± 1 meter accuracy.  Yesterday a 6 hour long
>> observation in a small field surrounded by forest converged to within 1
>> inch.  Dense forest canopy reduces the number of satellites that can be
>> tracked. Also, some times of day are better than others in terms of the
>> number of satellites and their geometry, s

Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[Michael . Dodd]

Coming back to the reference I mentioned much earlier in the string, one of the 
graphs is shown here: 
https://besjournals.onlinelibrary.wiley.com/action/downloadSupplement?doi=10.%2Fj.2041-210X.2011.00118.x=MEE3_118_sm_FigS2.doc

It shows the typical variation in location indicated by consumer gps units over 
time and how you may be able to get a better location by averaging over a 
longer period BUT that this location is still likely not to be the 'correct' 
location.

The particular graph shown here it is part of a 5 hour run with several 
consumer grade gps units and set of smartphones (only a small set of the data 
shown in that graph), the smartphones tested had some kind of averaging built 
in as they slowly got to within 1-2metres of the 'correct' location after about 
2 hours and stayed approximately there for the remains of the 5 hour run.

What I did not try is what would happen if you did the 2hours of averaging on 
several separate days, presumably on the archaeological fieldwork there might 
be the chance to do several days of 2 hour runs and with these averaged as well 
then half metre or even better might be possible but is not guaranteed.

One separate bit of information that could be of use for archaeological 
fieldwork is that besides the survey grade Leica dgps we also used 0.5m 
accuracy kit (the same leica kit but just using Egnos instead of Smartnet) to 
find buried markers for total station surveys. You would think that 0.5m 
accuracy plus a metal detector should be able to find the metal survey pin but 
it often took a very long time in rough grassland habitats so definitely having 
a way to get more accurate than 0.5m is better even if it is only to find the 
buried origin marks for total station. By comparision when full differential 
gps is switched on you walk exactly to the buried pin with no deviation and hit 
immediately.

From: Qgis-user  on behalf of QGIS.USER 

Sent: 27 May 2020 16:19
To: 'Garth Fletcher' ; qgis-user@lists.osgeo.org 

Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell 
phone

CAUTION: This mail comes from outside the University. Please consider this 
before opening attachments, clicking links, or acting on the content.

Hi Garth,
Thank you for the correction and the additional information. Much 
appreciated.

My current thinking is that in the archaeology we do, the intra-site (relative) 
measurements are quite good but what is inaccurate is the absolute 
measurements. We can set out our grids with cm accuracy but can only locate 
them on the ground with 10s of metre accuracy. It would be good to have a low 
cost way of establishing the absolute position even if that took time and/or 
was off-line.

Ray Carpenter,
Chapel Archaeology

-Original Message-
From: Garth Fletcher [mailto:ga...@jacqcad.com]
Sent: 27 May 2020 15:25
To: QGIS.USER; qgis-user@lists.osgeo.org
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell 
phone

Hi Ray,

Apologies for the typo - I had typed iGS3, but iG3s is the right number.

iGage http://www.igage.com>> iG3s, now replaced by the iG4 which 
adds Galileo
tracking but otherwise seems very similar to the iG3s. $2400 US.

These track satellites from the US GPS, Russian GLONASS, Chinese BeiDou
and, with the iG4, European Galileo constellations.

Their sole function is to record from all the satellites they can track.

They produce a RINEX format file which can be sent to a post processing
service such as Canada's Geodetic Surveys' CSRS-PPP:
<https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php?locale=en>

The longer the observation (recording) duration, the better CSRS-PPP can
converge to an accurate location.  In my experience in New Hampshire's
heavily wooded environment, a 30 to 45 minute observation time generally
gets me to better than ± 1 meter accuracy.  Yesterday a 6 hour long
observation in a small field surrounded by forest converged to within 1
inch.  Dense forest canopy reduces the number of satellites that can be
tracked. Also, some times of day are better than others in terms of the
number of satellites and their geometry, see:
   <https://www.gnssplanning.com/#/charts>

The iG3s was perfect for my specific conditions, but I think it is not
optimal where many locations within a site must be accurately measured
** relative ** to each other.

Such sites would be better served by differential measuring where two
receivers are used.  One is the "Base" which is kept in a fixed location
while the other is the "Rover" which is moved from place to place.

The Base constantly transmits its data to the Rover over a RF link.  As
long as both are fairly close (within a few kilometers of each other),
both see essentially identical satellite errors which can be cancelled
out to produce a very precise ** difference ** in location between Base
and Rover.

Note that the ab

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[Bernd Vogelgesang]

On 25.05.20 22:33, Garth Fletcher wrote:

Nicolas Cadieux wrote:

... The only way, as I see it, that GARMIN  is "privatizing the
geography", as you nicely put it, is by selling map to their map
capable units.  It would be nice to have the capability of uploading
our own maps to those units.  Apart from that, positions, waypoints  
and tracks can be uploaded and download with propitiatory and non
propitiatory software.  I believe QGIS had a plugin capable of doing
that with multiple consumer level GPS but I have never used it. ...


The plugin in question is:
"GarminCustomMap
 Export the current map canvas to a Garmin Custom Map (.kmz-file)
 The GarminCustomMap plugin exports the current map canvas to a .kmz-
 file, which is compatible with Garmin`s Custom Maps format for handheld
 GPS units. ..."

I used it to upload my own map with contours and property boundaries
of my region into my Garmin eTrex 20 and it worked very well.



well, I wasted precious hours of my life trying to fumble size-limited
aerials onto those mouse-cinema-boxes.
The plugin is no solution, it's just a workaround for a perverted
business model.

I'd rather spend three times more money on any other device than ever
touching again this crap.

Working on my phone is so much more efficient. Start QGIS, load a
publicly available WMS, put in your data, generate MBTILES and dump it
on the device. If there wasn't the lousy GPS accuracy.

Cheers,
Bernd


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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[Nicolas Cadieux]

Hi Garth,

I am also an archaeologist.  We use a single Sxblue 2 from GENEQ.  The unit was 
upgraded by the company so it’s takes in the Russian constellation now.  The 
unit is very precise. When we go out on the field, we let le unit run one a 
Bench mark for a few hours.  We then process that position  In PPP or using 
nrcan gps tower if we are close to one.  The company give a really good service 
helping with both software support and hardware.  As everything in made and 
designed in Québec, they can take the unit appart and change individual parts 
and chips.  We did that one as the Bluetooth chip was now longer capable of 
working with Windows 10 (more likely the other way around). It had been Made 
for Windows 95.  For a few extra bucks, they changed the gps chip also.  The 
unit is basically a brick (Square and heavy) that connects to an external 
device like a laptop or a tablet.  No screens or anywhere fancy.

https://geneq.com/land-surveying-geomatics/fr/fabricant/sxblue

Nicolas Cadieux
Ça va bien aller!

> Le 27 mai 2020 à 11:19, QGIS.USER  a écrit :
> 
> Hi Garth,
>Thank you for the correction and the additional information. Much 
> appreciated.
> 
> My current thinking is that in the archaeology we do, the intra-site 
> (relative) measurements are quite good but what is inaccurate is the absolute 
> measurements. We can set out our grids with cm accuracy but can only locate 
> them on the ground with 10s of metre accuracy. It would be good to have a low 
> cost way of establishing the absolute position even if that took time and/or 
> was off-line.
> 
> Ray Carpenter,
> Chapel Archaeology
> 
> -Original Message-
> From: Garth Fletcher [mailto:ga...@jacqcad.com] 
> Sent: 27 May 2020 15:25
> To: QGIS.USER; qgis-user@lists.osgeo.org
> Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a 
> cell phone
> 
> Hi Ray,
> 
> Apologies for the typo - I had typed iGS3, but iG3s is the right number.
> 
> iGage 
> <https://smex-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=www.igage.com=068947a3-968f-435b-8f88-0b9b8eb439a9=276d51547942e21b974d48c8cd7101aa75dd6e1a-f9ccd777f828c1b394629f942585917bb0a34506>
>  iG3s, now replaced by the iG4 which adds Galileo
> tracking but otherwise seems very similar to the iG3s. $2400 US.
> 
> These track satellites from the US GPS, Russian GLONASS, Chinese BeiDou
> and, with the iG4, European Galileo constellations.
> 
> Their sole function is to record from all the satellites they can track.
> 
> They produce a RINEX format file which can be sent to a post processing
> service such as Canada's Geodetic Surveys' CSRS-PPP:
> <https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php?locale=en>
> 
> The longer the observation (recording) duration, the better CSRS-PPP can
> converge to an accurate location.  In my experience in New Hampshire's
> heavily wooded environment, a 30 to 45 minute observation time generally
> gets me to better than ± 1 meter accuracy.  Yesterday a 6 hour long
> observation in a small field surrounded by forest converged to within 1
> inch.  Dense forest canopy reduces the number of satellites that can be
> tracked. Also, some times of day are better than others in terms of the
> number of satellites and their geometry, see:
>   <https://www.gnssplanning.com/#/charts>
> 
> The iG3s was perfect for my specific conditions, but I think it is not
> optimal where many locations within a site must be accurately me
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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[QGIS.USER]

Hi Garth,
Thank you for the correction and the additional information. Much 
appreciated.

My current thinking is that in the archaeology we do, the intra-site (relative) 
measurements are quite good but what is inaccurate is the absolute 
measurements. We can set out our grids with cm accuracy but can only locate 
them on the ground with 10s of metre accuracy. It would be good to have a low 
cost way of establishing the absolute position even if that took time and/or 
was off-line.

Ray Carpenter,
Chapel Archaeology

-Original Message-
From: Garth Fletcher [mailto:ga...@jacqcad.com] 
Sent: 27 May 2020 15:25
To: QGIS.USER; qgis-user@lists.osgeo.org
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell 
phone

Hi Ray,

Apologies for the typo - I had typed iGS3, but iG3s is the right number.

iGage  iG3s, now replaced by the iG4 which adds Galileo
tracking but otherwise seems very similar to the iG3s. $2400 US.

These track satellites from the US GPS, Russian GLONASS, Chinese BeiDou
and, with the iG4, European Galileo constellations.

Their sole function is to record from all the satellites they can track.

They produce a RINEX format file which can be sent to a post processing
service such as Canada's Geodetic Surveys' CSRS-PPP:
<https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php?locale=en>

The longer the observation (recording) duration, the better CSRS-PPP can
converge to an accurate location.  In my experience in New Hampshire's
heavily wooded environment, a 30 to 45 minute observation time generally
gets me to better than ± 1 meter accuracy.  Yesterday a 6 hour long
observation in a small field surrounded by forest converged to within 1
inch.  Dense forest canopy reduces the number of satellites that can be
tracked. Also, some times of day are better than others in terms of the
number of satellites and their geometry, see:
   <https://www.gnssplanning.com/#/charts>

The iG3s was perfect for my specific conditions, but I think it is not
optimal where many locations within a site must be accurately measured
** relative ** to each other.

Such sites would be better served by differential measuring where two
receivers are used.  One is the "Base" which is kept in a fixed location
while the other is the "Rover" which is moved from place to place.

The Base constantly transmits its data to the Rover over a RF link.  As
long as both are fairly close (within a few kilometers of each other),
both see essentially identical satellite errors which can be cancelled
out to produce a very precise ** difference ** in location between Base
and Rover.

Note that the absolute accuracy of their positions may not be as high,
but the relative accuracy can be at centimeter level.  In other words,
the absolute accuracy might be ± several meters, but the relative
accuracy will be ± centimeters.

Relative location is all that is needed for site mapping. Accurate
absolute location can then be determined by carefully measuring the
location of the Base, which only needs to be done once.

The major advantage is speed as there is no need for long observation
times at each location.  There is also no need for internet or cell
phone connectivity - the only requirement is that the Base be able to
transmit its data to the Rover at all locations of interest.

Earlier in this thread <https://emlid.com/reachrs/> was mentioned as one
source of such Base/Rover systems.  At $ 1600 per pair they woud be
less expensive than a single iG3s or iG4 and could be much more
effective.  However, I do not have any personal experience with such
instruments.

On 5/27/20 9:11 AM, QGIS.USER wrote:
> Hi Garth,
>   Thank you for some very useful data. Mine own experience in archaeology 
> fully supports your findings. Like most things in archaeology, money is 
> scare, time is plentiful:-)  So when you talk about getting sub-metre 
> accuracy using something called "iGS3", my interest peaked:-)  However, 
> despite a reasonably thorough Google, nothing relevant turned up. What is a 
> "iGS3" please?
> 
> Thanks in advance.
> 
> Ray Carpenter
> Chapel Archaeology.

Cordially
-- 
Garth Fletcher

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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[Garth Fletcher]

Hi Ray,

Apologies for the typo - I had typed iGS3, but iG3s is the right number.

iGage  iG3s, now replaced by the iG4 which adds Galileo
tracking but otherwise seems very similar to the iG3s. $2400 US.

These track satellites from the US GPS, Russian GLONASS, Chinese BeiDou
and, with the iG4, European Galileo constellations.

Their sole function is to record from all the satellites they can track.

They produce a RINEX format file which can be sent to a post processing
service such as Canada's Geodetic Surveys' CSRS-PPP:


The longer the observation (recording) duration, the better CSRS-PPP can
converge to an accurate location.  In my experience in New Hampshire's
heavily wooded environment, a 30 to 45 minute observation time generally
gets me to better than ± 1 meter accuracy.  Yesterday a 6 hour long
observation in a small field surrounded by forest converged to within 1
inch.  Dense forest canopy reduces the number of satellites that can be
tracked. Also, some times of day are better than others in terms of the
number of satellites and their geometry, see:
  

The iG3s was perfect for my specific conditions, but I think it is not
optimal where many locations within a site must be accurately measured
** relative ** to each other.

Such sites would be better served by differential measuring where two
receivers are used.  One is the "Base" which is kept in a fixed location
while the other is the "Rover" which is moved from place to place.

The Base constantly transmits its data to the Rover over a RF link.  As
long as both are fairly close (within a few kilometers of each other),
both see essentially identical satellite errors which can be cancelled
out to produce a very precise ** difference ** in location between Base
and Rover.

Note that the absolute accuracy of their positions may not be as high,
but the relative accuracy can be at centimeter level.  In other words,
the absolute accuracy might be ± several meters, but the relative
accuracy will be ± centimeters.

Relative location is all that is needed for site mapping. Accurate
absolute location can then be determined by carefully measuring the
location of the Base, which only needs to be done once.

The major advantage is speed as there is no need for long observation
times at each location.  There is also no need for internet or cell
phone connectivity - the only requirement is that the Base be able to
transmit its data to the Rover at all locations of interest.

Earlier in this thread  was mentioned as one
source of such Base/Rover systems.  At $ 1600 per pair they woud be
less expensive than a single iG3s or iG4 and could be much more
effective.  However, I do not have any personal experience with such
instruments.

On 5/27/20 9:11 AM, QGIS.USER wrote:

Hi Garth,
Thank you for some very useful data. Mine own experience in archaeology fully supports your 
findings. Like most things in archaeology, money is scare, time is plentiful:-)  So when you talk 
about getting sub-metre accuracy using something called "iGS3", my interest peaked:-)  
However, despite a reasonably thorough Google, nothing relevant turned up. What is a 
"iGS3" please?

Thanks in advance.

Ray Carpenter
Chapel Archaeology.


Cordially
--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[QGIS.USER]

Hi Garth,
Thank you for some very useful data. Mine own experience in archaeology 
fully supports your findings. Like most things in archaeology, money is scare, 
time is plentiful :-) So when you talk about getting sub-metre accuracy using 
something called "iGS3", my interest peaked :-) However, despite a reasonably 
thorough Google, nothing relevant turned up. What is a "iGS3" please?

Thanks in advance.

Ray Carpenter
Chapel Archaeology.  

-Original Message-
From: Qgis-user [mailto:qgis-user-boun...@lists.osgeo.org] On Behalf Of Garth 
Fletcher
Sent: 27 May 2020 04:29
To: qgis-user@lists.osgeo.org
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell 
phone

I gathered some field data using my Garmin eTrex 20.

It was placed in a fixed location in a small field and 17 readings were
taken (using Mark Waypoint) at various intervals between 11 AM and 10 PM
(EST).  The Garmin generally estimated the error band at 3 to 3.6 m. The
Garmin was receiving both US GPS and Russian GLONASS satellites, plus
WAIS (as indicated by a "D" in the Garmin's satellite signal bars).

The same location was accurately measured with a dual-freq iGS3 by
recording during the first ~ 6 hours and post-processing via CSRS-PPP
which resolved to a 95% probability error ellipse of 2.4 cm x 1.2 cm.

The CSRS report indicates that on average 10 to 11 satellites were being
tracked (range of 8 to 13).  The Garmin's display indicated a similar
number of satellites being tracked.

The Garmin waypoints were plotted on a 1 meter grid, along with the
precisely determined location. This plot can be downloaded from

<http://www.Mason-NH.org/Specials/GARMIN_TESTS.pdf>  (21 KB).

Worst case Garmin errors are > 6 m, close to twice the Garmin's
estimates - see above linked plot.

I am not convinced that averaging any couple such readings can do much
to increase the confidence level...

My conclusion is that if precision better than ± dozens of feet is
needed for a number of points (such as in an archeological dig), simple
hand-held instruments such as the Garmin (or cell phones) are not
suitable.

Using base/rover pairs, such as discussed earlier, is a much more
effective solution, albeit considerably more costly (~ 1500 USD). They
have the advantage of rapidly providing precise differential
measurements - which are what are all that is needed to map a site.

High position accuracy can be achieved with a single dual-frequency GNSS
receiver, such as the iGS3 I use, but at the cost of long duration
observations at each point.  In my experience an observation time of at
least 30 minutes is needed (in my wooded environment) to achieve ± 1
meter, and of 1 or more hours to achieve sub-meter accuracy in absolute
positional accuracy (as opposed to relative positional accuracy).
-- 
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from, a cell phone

[Garth Fletcher]

I gathered some field data using my Garmin eTrex 20.

It was placed in a fixed location in a small field and 17 readings were
taken (using Mark Waypoint) at various intervals between 11 AM and 10 PM
(EST).  The Garmin generally estimated the error band at 3 to 3.6 m. The
Garmin was receiving both US GPS and Russian GLONASS satellites, plus
WAIS (as indicated by a "D" in the Garmin's satellite signal bars).

The same location was accurately measured with a dual-freq iGS3 by
recording during the first ~ 6 hours and post-processing via CSRS-PPP
which resolved to a 95% probability error ellipse of 2.4 cm x 1.2 cm.

The CSRS report indicates that on average 10 to 11 satellites were being
tracked (range of 8 to 13).  The Garmin's display indicated a similar
number of satellites being tracked.

The Garmin waypoints were plotted on a 1 meter grid, along with the
precisely determined location. This plot can be downloaded from

  (21 KB).

Worst case Garmin errors are > 6 m, close to twice the Garmin's
estimates - see above linked plot.

I am not convinced that averaging any couple such readings can do much
to increase the confidence level...

My conclusion is that if precision better than ± dozens of feet is
needed for a number of points (such as in an archeological dig), simple
hand-held instruments such as the Garmin (or cell phones) are not
suitable.

Using base/rover pairs, such as discussed earlier, is a much more
effective solution, albeit considerably more costly (~ 1500 USD). They
have the advantage of rapidly providing precise differential
measurements - which are what are all that is needed to map a site.

High position accuracy can be achieved with a single dual-frequency GNSS
receiver, such as the iGS3 I use, but at the cost of long duration
observations at each point.  In my experience an observation time of at
least 30 minutes is needed (in my wooded environment) to achieve ± 1
meter, and of 1 or more hours to achieve sub-meter accuracy in absolute
positional accuracy (as opposed to relative positional accuracy).
--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Falk Huettmann]

Dear Jochen et al,

...thanks,
but it is 100% incorrect that Google Earth made satellite data available,
and/or for free, e.g. Landsat.
The opposite is the case (Landsat was made open by the Clinton
administration etc much before that, by law. It's widely paid by US tax
money btw) ;
so Google Earth just used a nice and shiny PUBLIC image set and copyrighted
it, value-added as a map background; more or less.
There are no 8 bands in the Google Earth Landsat set to use; just a flat
image file!
What's the progress other than the hype and them selling public stuff and
making it hard for GIS users etc ?
Who owns the space, the satellites ?

It's also incorrect to call Google Earth and its format a GIS; Google Earth
is just a visualizing tool, kmz is pretty awful for any serious GIS work
and database work (just like shapefiles are, even worse in Geodatabases;
all commercial btw
and based on dBASE style).

OpenStreetMaps cannot copyright words, as a product (an Open Street Map
that is, public common words found in any dictionary).
Apple does not own apples neither, nor snow leopards.

If somebody occupies, measures and uses public spaces, and then gets 'the
best' (hi res) data on the market, e.g. for roads,
that's clearly a monopoly, and should be treated as such, and with ethics.
It has many many implications in capitalism and worse, e.g.
https://www.gnu.org/philosophy/why-copyleft.en.html

So the easier,  and the better a format is described, the better for
everybody to use (if that's the purpose).
ISO comes to play, or VM, GNU etc .

We have seen very bad things last 40 years in the GIS world, and it's
little progress.
Certainly true for the EU and the German Katasteraemter, or EU Remote
Sensing or EU science (see Max Planck Institutes etc, Fisheries data,
cancer data).
What they call open access usually is not, and very clumsy at best; widely
underachieving for decades.

It is very important here to understand and perceive those things
correctly, because
otherwise we end up with more private and commercial intrusions.
Bad impacts can be seen world-wide already, all the time.
GARMIN is among them; just see COVID examples.

QGIS is a shining example and outlier, beyond R (not a GIS btw).

Any public librarian can tell you their stories about it (and consider many
libraries being short-handed most times, hardly afloat for money).

It's a very important subject, Just think of use of hi res data for drones,
the decaying public good, global society etc
An example here: https://en.wikipedia.org/wiki/Bowling_Alone

That's my experience on the topic and why I shared it here in some detail;
thanks.

Keep me posted please; very best
   Falk Huettmann PhD, Professor
 University of Alaska Fairbanks










On Mon, May 25, 2020 at 12:28 PM  wrote:

> Hi,
>
> while I agree that there are lots of bad examples of proprietary formats,
> I want to say a few words to some of your examples:
> It is true that OpenStreetMap data is difficult to handle -  this is not
> because it is closed, but because it is open. When the project was started
> the goal was to make it as easy as possible for people to contribute to the
> dataset. Thus there are few restrictions which makes it difficult to render
> or process the data. But the alternative would probably have been to
> discuss the data format for years instead of building an amazing open
> dataset...
>
> While Garmin makes it difficult to upload custom maps to their units as
> Nicolas wrote, many of their devices can be accessed as a USB drive and
> waypoint/track data can simply be copied as .GPX-files. I have seen many
> devices needing special software to transfer data, so this is actually easy.
>
> When Google Earth first came to be, it was amazing - access to satellite
> or aerial imagery had been expensive and difficult before. So I don't have
> a problem with the fact that Google didn't make the data available for
> everyone to use (probably license restrictions prohibit this).
>
> Text files aren't often that simple - there are different encodings for
> example which aren't advertised in the files, so you often have to guess to
> get special characters right. They have no inbuilt validity checks, so
> errors can not be easily recognised. In most use cases, structured (XML)
> formats are preferable. And especially for large datasets, you get much
> better performance and functionality using other formats like Geopackage.
> The point in my opinion is that a format is open and well documented.
>
> Of course it is great if geodata is available to the public. In the EU,
> there has been a lot of movement in the last years with more and more data
> becoming available under open licenses, let's hope this continues.
>
> Regards,
> Jochen
>
> Am 25.05.20 um 20:55 schrieb Falk Huettmann:
>
> Dear Chris et al,
>
> ...by using certain specific/clumsy formats -poorly documented ones - you
> can virtually exclude
> people from data and from Remote Sensing data and GPS etc.
> Google 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[chris hermansen]

Falk and list,

On Mon, May 25, 2020 at 11:55 AM Falk Huettmann 
wrote:

> Dear Chris et al,
>
> ...by using certain specific/clumsy formats -poorly documented ones - you
> can virtually exclude
> people from data and from Remote Sensing data and GPS etc.
> Google Earth as a  classic example, and GARMIN as another, or ESRI files,
> certainly NetCDF or many R packages even.
>
> In reality, you will see that all what is shiny and new - in demand- is to
> be sold, and usually not well publically shared.
> It takes many steps to get around it, if even that.
>
> While I have used OpenStreet maps, it was very clumsy; more bad examples
> exist, e.g. lack of metadata.
> Whatever companies tell ya, they want to sell more stuff (sell PR, or
> might face bankruptcy otherwise).
>

I get your point about commercial interests.  But I think you're missing
three very important details here.

First, OpenStreetMap is provided by the OpenStreetMap Foundation see
https://www.openstreetmap.org/about which is not a company trying to sell
stuff.

Second, from the OpenStreetMap website
https://www.openstreetmap.org/#map=5/51.500/-0.100

OpenStreetMap data is licensed under the Open Data Commons Open Database
> License  (ODbL).
>

preamble to which is:

The Open Database License (ODbL) is a license agreement intended to allow
> users to freely share, modify, and use this Database while maintaining this
> same freedom for others. Many databases are covered by copyright, and
> therefore this document licenses these rights. Some jurisdictions, mainly
> in the European Union, have specific rights that cover databases, and so
> the ODbL addresses these rights, too. Finally, the ODbL is also an
> agreement in contract for users of this Database to act in certain ways in
> return for accessing this Database.
>

So it's open by definition.


> And it is my hope that with QGIS we get to open access and open source,
> of these data, and any other.
>
> My format of choice is plain and simple ASCII text files for those
> reasons, perhaps using the
> Virtual Machine as a platform forever (well, as long as that is
> reasonable, but not commercially driven).
>


Third, OpenStreetMap data is easily downloaded in well-documented XML
format.  It's readable and easily parsed by any number of open source XML
parsers in Python, Java, etc.  There is a lot of useful metadata
incorporated in it.

It loads directly into QGIS without fuss (I just confirmed this by
downloading some data from the OpenStreetMap site and loading into my QGIS
3.12 running on my desktop).

It's better than plain and simple ASCII text because, well, a few reasons I
can think of:

   1. it's UTF-8 not ASCII, so we get more than 128 or 256 characters
   2. its structure is documented
   3. it's well-known by other software out there (e.g. QGIS)
   4. it's readable


> Keep me posted please; very best & thanks
>

Maybe you should take another look at OpenStreetMap.

 Falk Huettmann
>
>
> On Mon, May 25, 2020 at 10:19 AM chris hermansen 
> wrote:
>
>> Falk and list;
>>
>> On Mon, May 25, 2020 at 10:48 AM Falk Huettmann 
>> wrote:
>>
>>> Dear List,
>>> I think these GPS high resolution suggestions are great;
>>> thanks.
>>>
>>> But my real interest/question here is, how can we bring it home to QGIS ?
>>>
>>> I see GARMIN essentially trying to sell and impose on us their GIS
>>> system,
>>> same applies to OpenStreet Maps etc etc. So they try to privatize
>>> geography and public space and information,
>>> which I am mostly opposed to.
>>>
>>
>> How is OpenStreetMap (I assume when you say "OpenStreet Maps" you mean
>> "OpenStreetMap") trying "to privatize geography and public space and
>> information"?   Not trying to start an argument here; this just seems
>> completely contrary to what I know of OpenStreetMap, whose data is licensed
>> under https://opendatacommons.org/licenses/odbl/1.0/
>>
>>
>>> Instead, I wonder how we can use QGIS and release the commercial
>>> data into Open Source and public use ?
>>> That's for HIGH RESOLUTION data discussed here.
>>>
>>> Thanks for such questions and solutions.
>>>
>>
>> [stuff deleted]
>>
>>
>> --
>> Chris Hermansen · clhermansen "at" gmail "dot" com
>>
>> C'est ma façon de parler.
>>
>

-- 
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell, phone

[Garth Fletcher]

Nicolas Cadieux wrote:
... The only way, as I see it, that GARMIN  is "privatizing the geography", 
as you nicely put it,  is by selling map to their map capable units.  It 
would be nice to have the capability of uploading our own maps to those 
units.  Apart from that, positions, waypoints   and tracks can be 
uploaded and download with propitiatory and non propitiatory software.  
I believe QGIS had a plugin capable of doing that with multiple consumer 
level GPS but I have never used it. ...


The plugin in question is:
"GarminCustomMap
 Export the current map canvas to a Garmin Custom Map (.kmz-file)
 The GarminCustomMap plugin exports the current map canvas to a .kmz-
 file, which is compatible with Garmin`s Custom Maps format for handheld
 GPS units. ..."

I used it to upload my own map with contours and property boundaries
of my region into my Garmin eTrex 20 and it worked very well.
--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[j . huber]

Hi,

while I agree that there are lots of bad examples of proprietary
formats, I want to say a few words to some of your examples:
It is true that OpenStreetMap data is difficult to handle -  this is not
because it is closed, but because it is open. When the project was
started the goal was to make it as easy as possible for people to
contribute to the dataset. Thus there are few restrictions which makes
it difficult to render or process the data. But the alternative would
probably have been to discuss the data format for years instead of
building an amazing open dataset...

While Garmin makes it difficult to upload custom maps to their units as
Nicolas wrote, many of their devices can be accessed as a USB drive and
waypoint/track data can simply be copied as .GPX-files. I have seen many
devices needing special software to transfer data, so this is actually easy.

When Google Earth first came to be, it was amazing - access to satellite
or aerial imagery had been expensive and difficult before. So I don't
have a problem with the fact that Google didn't make the data available
for everyone to use (probably license restrictions prohibit this).

Text files aren't often that simple - there are different encodings for
example which aren't advertised in the files, so you often have to guess
to get special characters right. They have no inbuilt validity checks,
so errors can not be easily recognised. In most use cases, structured
(XML) formats are preferable. And especially for large datasets, you get
much better performance and functionality using other formats like
Geopackage. The point in my opinion is that a format is open and well
documented.

Of course it is great if geodata is available to the public. In the EU,
there has been a lot of movement in the last years with more and more
data becoming available under open licenses, let's hope this continues.

Regards,
Jochen

Am 25.05.20 um 20:55 schrieb Falk Huettmann:
> Dear Chris et al,
>
> ...by using certain specific/clumsy formats -poorly documented ones -
> you can virtually exclude
> people from data and from Remote Sensing data and GPS etc.
> Google Earth as a  classic example, and GARMIN as another, or ESRI
> files, certainly NetCDF or many R packages even.
>
> In reality, you will see that all what is shiny and new - in demand-
> is to be sold, and usually not well publically shared.
> It takes many steps to get around it, if even that.
>
> While I have used OpenStreet maps, it was very clumsy; more bad
> examples exist, e.g. lack of metadata.
> Whatever companies tell ya, they want to sell more stuff (sell PR, or
> might face bankruptcy otherwise).
>
> And it is my hope that with QGIS we get to open access and open source,
> of these data, and any other.
>
> My format of choice is plain and simple ASCII text files for those
> reasons, perhaps using the 
> Virtual Machine as a platform forever (well, as long as that is
> reasonable, but not commercially driven).
>
> Keep me posted please; very best & thanks
>      Falk Huettmann
>
>
> On Mon, May 25, 2020 at 10:19 AM chris hermansen
> mailto:clherman...@gmail.com>> wrote:
>
> Falk and list;
>
> On Mon, May 25, 2020 at 10:48 AM Falk Huettmann
> mailto:fhuettm...@alaska.edu>> wrote:
>
> Dear List,
> I think these GPS high resolution suggestions are great; 
> thanks.
>
> But my real interest/question here is, how can we bring it
> home to QGIS ?
>
> I see GARMIN essentially trying to sell and impose on us their
> GIS system,
> same applies to OpenStreet Maps etc etc. So they try to
> privatize geography and public space and information, 
> which I am mostly opposed to.
>
>
> How is OpenStreetMap (I assume when you say "OpenStreet Maps" you
> mean "OpenStreetMap") trying "to privatize geography and public
> space and information"?   Not trying to start an argument here;
> this just seems completely contrary to what I know of
> OpenStreetMap, whose data is licensed under
> https://opendatacommons.org/licenses/odbl/1.0/
>
>
> Instead, I wonder how we can use QGIS and release the commercial
> data into Open Source and public use ?
> That's for HIGH RESOLUTION data discussed here.
>
> Thanks for such questions and solutions.
>
>
> [stuff deleted]
>
>
> -- 
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
>
>
> ___
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user


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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Nicolas Cadieux]

und the missing measurements and lack of algorithms in
consumer
grade chips.

Then it depends on the capabilities of the device to receive
satellites
of all systems (one or multiple frequencies/signals) and be
able to
apply correction data (a question of algorithms). For better
equipment
the prices rise quickly.

There are some low cost devices evolving, a new chip was recently
announced: Skytraq PX1122R for about $100. Could be tested
with a break
out board and antenna, e.g. see board at navspark shop. The
module even
supports PPP, which might be especially interesting where
mobile network
is not available.

https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/

Other low cost solution were mentioned (emlid/REACH,
Catalyst, etc).


Am 23.05.20 um 21:51 schrieb Michael.Dodd:
> One app that claims to do a lot of what high precions gps
does is> Mobile Topographer Free – Apps on Google Play

> 2) Software

On Android I was able to get the external signal into the
system, you
need the app "Bluetoth GPS" (or similar) or a USB2serial +
app (better
avoid tiny plugs and large cables during field work).
Additionally you
need to override the internal GPS position with the Blue GPS
App in the
developer settings (mock provider).

My impression was, that most Android applications target the
accuracy of
the device only, so e.g.

* you cannot zoom to cm-levels, only ~100m
* not many proper GIS Apps are available, most are expensive
* Tracking usually does not rely on cm-grade positions, so
the apps are
not made for it

One particular thing is, that with high accuracy of the
signal, an
internal computation in single precision float will not
suffice (all
computations must be in double precision), and you may end up
with a cut
off of the last position digits, e.g. if you have 8 digits, 4
before and
4 after the decimal separator (e.g. in DDMM. format),
then you end
up with coordinates cut down to 2-3 decimeters in the real world
(typical GPS mouse output, not so uncommon).

So, looking into that aspect may be required, and only few
Apps may
implement that (e.g. expensive "surveyor" apps for
professionals? did
not test).
BTW, sponsoring the double accuracy implementation for QField is
welcome, as mentioned ot the webpage. It is already a very
usable and
FLOSS GIS solution for the field, especially useful if you
have a QGIS
workflow already ;)

Finding proper solutions and recommendations still required...



>

> *From:* Qgis-user mailto:qgis-user-boun...@lists.osgeo.org>> on behalf of
> j.hu...@post-ist-da.de <mailto:j.hu...@post-ist-da.de>
mailto:j.hu...@post-ist-da.de>>
> *Sent:* 23 May 2020 20:35
> *To:* qgis-user@lists.osgeo.org
<mailto:qgis-user@lists.osgeo.org> mailto:qgis-user@lists.osgeo.org>>
    > *Subject:* Re: [Qgis-user] wishing for accurate
lattitude/longitude from
> a cell phone
>
>
> Hi Steve,
>
> I think there are two different aspects to your question:
> 1) Accuracy of GPS Devices
> I agree with others that you can't expect a better accuracy
than the 10
> to 30 feet you observed with a smartphone or a simple
handheld GPS. This
> might improve by averaging, but this takes time. Survey
grade GPS
> devices are very expensive. It is possible to get good
modules and
> antennas as components, but building a complete GNSS system
requires
> time and skill. This would reduce cost, but only to several
hundred
> instead of several thousand dollars, so this is no option
in your case.
> Besides, you will still need a correction data service
(usually costly)
> or use two receivers (rover and base).
> So you probably have to stick with your phone, which is
more flexible
> regarding the software than a handheld GPS.
>
> 2) Software
> The accuracy of the recorded position should not depend on
where you tap
> the screen - a good app should allow to record the current
GPS position.
> I am using Locus Map (Asamm Softwa

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Falk Huettmann]

Dear Chris et al,

...by using certain specific/clumsy formats -poorly documented ones - you
can virtually exclude
people from data and from Remote Sensing data and GPS etc.
Google Earth as a  classic example, and GARMIN as another, or ESRI files,
certainly NetCDF or many R packages even.

In reality, you will see that all what is shiny and new - in demand- is to
be sold, and usually not well publically shared.
It takes many steps to get around it, if even that.

While I have used OpenStreet maps, it was very clumsy; more bad examples
exist, e.g. lack of metadata.
Whatever companies tell ya, they want to sell more stuff (sell PR, or might
face bankruptcy otherwise).

And it is my hope that with QGIS we get to open access and open source,
of these data, and any other.

My format of choice is plain and simple ASCII text files for those reasons,
perhaps using the
Virtual Machine as a platform forever (well, as long as that is reasonable,
but not commercially driven).

Keep me posted please; very best & thanks
 Falk Huettmann


On Mon, May 25, 2020 at 10:19 AM chris hermansen 
wrote:

> Falk and list;
>
> On Mon, May 25, 2020 at 10:48 AM Falk Huettmann 
> wrote:
>
>> Dear List,
>> I think these GPS high resolution suggestions are great;
>> thanks.
>>
>> But my real interest/question here is, how can we bring it home to QGIS ?
>>
>> I see GARMIN essentially trying to sell and impose on us their GIS system,
>> same applies to OpenStreet Maps etc etc. So they try to privatize
>> geography and public space and information,
>> which I am mostly opposed to.
>>
>
> How is OpenStreetMap (I assume when you say "OpenStreet Maps" you mean
> "OpenStreetMap") trying "to privatize geography and public space and
> information"?   Not trying to start an argument here; this just seems
> completely contrary to what I know of OpenStreetMap, whose data is licensed
> under https://opendatacommons.org/licenses/odbl/1.0/
>
>
>> Instead, I wonder how we can use QGIS and release the commercial
>> data into Open Source and public use ?
>> That's for HIGH RESOLUTION data discussed here.
>>
>> Thanks for such questions and solutions.
>>
>
> [stuff deleted]
>
>
> --
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
>
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[qgis-user]

  
  
On 5/25/2020 11:31 AM, chris hermansen
  wrote:


  
One of many articles that may be of interest https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all
  

That module doesn't appear to output the sort of information
required for RTK correction. The uBlox m8t, available for about $20
on AliExpress and no doubt other places, does provide that sort of
information which could be used to post-process location information
to higher accuracy. The NEO 6M, at half that price or less, will
also do so, with a little more effort. 

  

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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[chris hermansen]

Falk and list;

On Mon, May 25, 2020 at 10:48 AM Falk Huettmann 
wrote:

> Dear List,
> I think these GPS high resolution suggestions are great;
> thanks.
>
> But my real interest/question here is, how can we bring it home to QGIS ?
>
> I see GARMIN essentially trying to sell and impose on us their GIS system,
> same applies to OpenStreet Maps etc etc. So they try to privatize
> geography and public space and information,
> which I am mostly opposed to.
>

How is OpenStreetMap (I assume when you say "OpenStreet Maps" you mean
"OpenStreetMap") trying "to privatize geography and public space and
information"?   Not trying to start an argument here; this just seems
completely contrary to what I know of OpenStreetMap, whose data is licensed
under https://opendatacommons.org/licenses/odbl/1.0/


> Instead, I wonder how we can use QGIS and release the commercial
> data into Open Source and public use ?
> That's for HIGH RESOLUTION data discussed here.
>
> Thanks for such questions and solutions.
>

[stuff deleted]


-- 
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Falk Huettmann]

Dear List,
I think these GPS high resolution suggestions are great;
thanks.

But my real interest/question here is, how can we bring it home to QGIS ?

I see GARMIN essentially trying to sell and impose on us their GIS system,
same applies to OpenStreet Maps etc etc. So they try to privatize geography
and public space and information,
which I am mostly opposed to.

Instead, I wonder how we can use QGIS and release the commercial
data into Open Source and public use ?
That's for HIGH RESOLUTION data discussed here.

Thanks for such questions and solutions.

Very best
   Falk Huettmann PhD, Professor
Uni of Alaska Fairbanks


On Mon, May 25, 2020 at 9:41 AM Kirk Schmidt 
wrote:

> Hi List:
>
> In my experience, the key is writing output in rinex format so that the
> rover data can be corrected either using PPP if you can collect your GPS
> data over and extended period of time or use pre-existing (or self
> deployed) base station over a know coordinate to provide correction data.
> Most consumer grade units output the final position solution, not detailed
> satellite data which is required for followup processing.
>
> Kirk Schmidt
> On 5/25/2020 2:31 PM, chris hermansen wrote:
>
> Martin and list,
>
> To me, in general, I think I would try to go with a Raspberry Pi based
> solution.  The hardware isn't all that expensive and the easy ability to do
> stuff directly with the output of the device in Python or some other
> programming language seems to be preferable to messing around with Android
> or iOS applications.
>
> One of many articles that may be of interest
> https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all
>
> On Mon, May 25, 2020 at 9:25 AM Martin Weis 
> wrote:
>
>> Dear list,
>>
>> I would like to add some things here, since I am trying to use RTK GPS
>> in the field with mobile devices.
>>
>> > 1) Accuracy of GPS Devices
>>
>> RTK GPS or any more precice GPS technology will be external, you cannot
>> get around the missing measurements and lack of algorithms in consumer
>> grade chips.
>>
>> Then it depends on the capabilities of the device to receive satellites
>> of all systems (one or multiple frequencies/signals) and be able to
>> apply correction data (a question of algorithms). For better equipment
>> the prices rise quickly.
>>
>> There are some low cost devices evolving, a new chip was recently
>> announced: Skytraq PX1122R for about $100. Could be tested with a break
>> out board and antenna, e.g. see board at navspark shop. The module even
>> supports PPP, which might be especially interesting where mobile network
>> is not available.
>>
>> https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/
>>
>> Other low cost solution were mentioned (emlid/REACH, Catalyst, etc).
>>
>>
>> Am 23.05.20 um 21:51 schrieb Michael.Dodd:
>> > One app that claims to do a lot of what high precions gps does is>
>> Mobile Topographer Free – Apps on Google Play
>>
>> > 2) Software
>>
>> On Android I was able to get the external signal into the system, you
>> need the app "Bluetoth GPS" (or similar) or a USB2serial + app (better
>> avoid tiny plugs and large cables during field work). Additionally you
>> need to override the internal GPS position with the Blue GPS App in the
>> developer settings (mock provider).
>>
>> My impression was, that most Android applications target the accuracy of
>> the device only, so e.g.
>>
>> * you cannot zoom to cm-levels, only ~100m
>> * not many proper GIS Apps are available, most are expensive
>> * Tracking usually does not rely on cm-grade positions, so the apps are
>> not made for it
>>
>> One particular thing is, that with high accuracy of the signal, an
>> internal computation in single precision float will not suffice (all
>> computations must be in double precision), and you may end up with a cut
>> off of the last position digits, e.g. if you have 8 digits, 4 before and
>> 4 after the decimal separator (e.g. in DDMM. format), then you end
>> up with coordinates cut down to 2-3 decimeters in the real world
>> (typical GPS mouse output, not so uncommon).
>>
>> So, looking into that aspect may be required, and only few Apps may
>> implement that (e.g. expensive "surveyor" apps for professionals? did
>> not test).
>> BTW, sponsoring the double accuracy implementation for QField is
>> welcome, as mentioned ot the webpage. It is already a very usable and
>> FLOSS GIS solution for the field, especially useful if you have a QGIS

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Kirk Schmidt]

Hi List:

In my experience, the key is writing output in rinex format so that the 
rover data can be corrected either using PPP if you can collect your GPS 
data over and extended period of time or use pre-existing (or self 
deployed) base station over a know coordinate to provide correction 
data.  Most consumer grade units output the final position solution, not 
detailed satellite data which is required for followup processing.


Kirk Schmidt

On 5/25/2020 2:31 PM, chris hermansen wrote:

Martin and list,

To me, in general, I think I would try to go with a Raspberry Pi based 
solution.  The hardware isn't all that expensive and the easy ability 
to do stuff directly with the output of the device in Python or some 
other programming language seems to be preferable to messing around 
with Android or iOS applications.


One of many articles that may be of interest 
https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all


On Mon, May 25, 2020 at 9:25 AM Martin Weis 
mailto:martin.weis.newsadr...@gmx.de>> 
wrote:


Dear list,

I would like to add some things here, since I am trying to use RTK GPS
in the field with mobile devices.

> 1) Accuracy of GPS Devices

RTK GPS or any more precice GPS technology will be external, you
cannot
get around the missing measurements and lack of algorithms in consumer
grade chips.

Then it depends on the capabilities of the device to receive
satellites
of all systems (one or multiple frequencies/signals) and be able to
apply correction data (a question of algorithms). For better equipment
the prices rise quickly.

There are some low cost devices evolving, a new chip was recently
announced: Skytraq PX1122R for about $100. Could be tested with a
break
out board and antenna, e.g. see board at navspark shop. The module
even
supports PPP, which might be especially interesting where mobile
network
is not available.

https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/

Other low cost solution were mentioned (emlid/REACH, Catalyst, etc).


Am 23.05.20 um 21:51 schrieb Michael.Dodd:
> One app that claims to do a lot of what high precions gps does
is> Mobile Topographer Free – Apps on Google Play

> 2) Software

On Android I was able to get the external signal into the system, you
need the app "Bluetoth GPS" (or similar) or a USB2serial + app (better
avoid tiny plugs and large cables during field work). Additionally you
need to override the internal GPS position with the Blue GPS App
in the
developer settings (mock provider).

My impression was, that most Android applications target the
accuracy of
the device only, so e.g.

* you cannot zoom to cm-levels, only ~100m
* not many proper GIS Apps are available, most are expensive
* Tracking usually does not rely on cm-grade positions, so the
apps are
not made for it

One particular thing is, that with high accuracy of the signal, an
internal computation in single precision float will not suffice (all
computations must be in double precision), and you may end up with
a cut
off of the last position digits, e.g. if you have 8 digits, 4
before and
4 after the decimal separator (e.g. in DDMM. format), then you end
up with coordinates cut down to 2-3 decimeters in the real world
(typical GPS mouse output, not so uncommon).

So, looking into that aspect may be required, and only few Apps may
implement that (e.g. expensive "surveyor" apps for professionals? did
not test).
BTW, sponsoring the double accuracy implementation for QField is
welcome, as mentioned ot the webpage. It is already a very usable and
FLOSS GIS solution for the field, especially useful if you have a QGIS
workflow already ;)

Finding proper solutions and recommendations still required...



>

> *From:* Qgis-user mailto:qgis-user-boun...@lists.osgeo.org>> on behalf of
> j.hu...@post-ist-da.de <mailto:j.hu...@post-ist-da.de>
mailto:j.hu...@post-ist-da.de>>
> *Sent:* 23 May 2020 20:35
> *To:* qgis-user@lists.osgeo.org
<mailto:qgis-user@lists.osgeo.org> mailto:qgis-user@lists.osgeo.org>>
> *Subject:* Re: [Qgis-user] wishing for accurate
lattitude/longitude from
> a cell phone
>
>
> Hi Steve,
>
> I think there are two different aspects to your question:
> 1) Accuracy of GPS Devices
> I agree with others that you can't expect a better accuracy than
the 10
> to 30 feet you observed with a smartphone or a simple handheld
GPS. This
> might improve by averaging, but this takes time. Survey grade GPS
> device

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[chris hermansen]

Martin and list,

To me, in general, I think I would try to go with a Raspberry Pi based
solution.  The hardware isn't all that expensive and the easy ability to do
stuff directly with the output of the device in Python or some other
programming language seems to be preferable to messing around with Android
or iOS applications.

One of many articles that may be of interest
https://learn.adafruit.com/adafruit-ultimate-gps-on-the-raspberry-pi?view=all

On Mon, May 25, 2020 at 9:25 AM Martin Weis 
wrote:

> Dear list,
>
> I would like to add some things here, since I am trying to use RTK GPS
> in the field with mobile devices.
>
> > 1) Accuracy of GPS Devices
>
> RTK GPS or any more precice GPS technology will be external, you cannot
> get around the missing measurements and lack of algorithms in consumer
> grade chips.
>
> Then it depends on the capabilities of the device to receive satellites
> of all systems (one or multiple frequencies/signals) and be able to
> apply correction data (a question of algorithms). For better equipment
> the prices rise quickly.
>
> There are some low cost devices evolving, a new chip was recently
> announced: Skytraq PX1122R for about $100. Could be tested with a break
> out board and antenna, e.g. see board at navspark shop. The module even
> supports PPP, which might be especially interesting where mobile network
> is not available.
>
> https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/
>
> Other low cost solution were mentioned (emlid/REACH, Catalyst, etc).
>
>
> Am 23.05.20 um 21:51 schrieb Michael.Dodd:
> > One app that claims to do a lot of what high precions gps does is>
> Mobile Topographer Free – Apps on Google Play
>
> > 2) Software
>
> On Android I was able to get the external signal into the system, you
> need the app "Bluetoth GPS" (or similar) or a USB2serial + app (better
> avoid tiny plugs and large cables during field work). Additionally you
> need to override the internal GPS position with the Blue GPS App in the
> developer settings (mock provider).
>
> My impression was, that most Android applications target the accuracy of
> the device only, so e.g.
>
> * you cannot zoom to cm-levels, only ~100m
> * not many proper GIS Apps are available, most are expensive
> * Tracking usually does not rely on cm-grade positions, so the apps are
> not made for it
>
> One particular thing is, that with high accuracy of the signal, an
> internal computation in single precision float will not suffice (all
> computations must be in double precision), and you may end up with a cut
> off of the last position digits, e.g. if you have 8 digits, 4 before and
> 4 after the decimal separator (e.g. in DDMM. format), then you end
> up with coordinates cut down to 2-3 decimeters in the real world
> (typical GPS mouse output, not so uncommon).
>
> So, looking into that aspect may be required, and only few Apps may
> implement that (e.g. expensive "surveyor" apps for professionals? did
> not test).
> BTW, sponsoring the double accuracy implementation for QField is
> welcome, as mentioned ot the webpage. It is already a very usable and
> FLOSS GIS solution for the field, especially useful if you have a QGIS
> workflow already ;)
>
> Finding proper solutions and recommendations still required...
>
>
>
> > ----------------
> > *From:* Qgis-user  on behalf of
> > j.hu...@post-ist-da.de 
> > *Sent:* 23 May 2020 20:35
> > *To:* qgis-user@lists.osgeo.org 
> > *Subject:* Re: [Qgis-user] wishing for accurate lattitude/longitude from
> > a cell phone
> >
> >
> > Hi Steve,
> >
> > I think there are two different aspects to your question:
> > 1) Accuracy of GPS Devices
> > I agree with others that you can't expect a better accuracy than the 10
> > to 30 feet you observed with a smartphone or a simple handheld GPS. This
> > might improve by averaging, but this takes time. Survey grade GPS
> > devices are very expensive. It is possible to get good modules and
> > antennas as components, but building a complete GNSS system requires
> > time and skill. This would reduce cost, but only to several hundred
> > instead of several thousand dollars, so this is no option in your case.
> > Besides, you will still need a correction data service (usually costly)
> > or use two receivers (rover and base).
> > So you probably have to stick with your phone, which is more flexible
> > regarding the software than a handheld GPS.
> >
> > 2) Software
> > The accuracy of the recorded position should not depend on where you 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Martin Weis]

Dear list,

I would like to add some things here, since I am trying to use RTK GPS
in the field with mobile devices.

> 1) Accuracy of GPS Devices

RTK GPS or any more precice GPS technology will be external, you cannot
get around the missing measurements and lack of algorithms in consumer
grade chips.

Then it depends on the capabilities of the device to receive satellites
of all systems (one or multiple frequencies/signals) and be able to
apply correction data (a question of algorithms). For better equipment
the prices rise quickly.

There are some low cost devices evolving, a new chip was recently
announced: Skytraq PX1122R for about $100. Could be tested with a break
out board and antenna, e.g. see board at navspark shop. The module even
supports PPP, which might be especially interesting where mobile network
is not available.
https://navspark.mybigcommerce.com/px1122r-evb-px1122r-multi-band-quad-gnss-rtk-evaluation-board/

Other low cost solution were mentioned (emlid/REACH, Catalyst, etc).


Am 23.05.20 um 21:51 schrieb Michael.Dodd:
> One app that claims to do a lot of what high precions gps does is> Mobile 
> Topographer Free – Apps on Google Play

> 2) Software

On Android I was able to get the external signal into the system, you
need the app "Bluetoth GPS" (or similar) or a USB2serial + app (better
avoid tiny plugs and large cables during field work). Additionally you
need to override the internal GPS position with the Blue GPS App in the
developer settings (mock provider).

My impression was, that most Android applications target the accuracy of
the device only, so e.g.

* you cannot zoom to cm-levels, only ~100m
* not many proper GIS Apps are available, most are expensive
* Tracking usually does not rely on cm-grade positions, so the apps are
not made for it

One particular thing is, that with high accuracy of the signal, an
internal computation in single precision float will not suffice (all
computations must be in double precision), and you may end up with a cut
off of the last position digits, e.g. if you have 8 digits, 4 before and
4 after the decimal separator (e.g. in DDMM. format), then you end
up with coordinates cut down to 2-3 decimeters in the real world
(typical GPS mouse output, not so uncommon).

So, looking into that aspect may be required, and only few Apps may
implement that (e.g. expensive "surveyor" apps for professionals? did
not test).
BTW, sponsoring the double accuracy implementation for QField is
welcome, as mentioned ot the webpage. It is already a very usable and
FLOSS GIS solution for the field, especially useful if you have a QGIS
workflow already ;)

Finding proper solutions and recommendations still required...



> 
> *From:* Qgis-user  on behalf of
> j.hu...@post-ist-da.de 
> *Sent:* 23 May 2020 20:35
> *To:* qgis-user@lists.osgeo.org 
> *Subject:* Re: [Qgis-user] wishing for accurate lattitude/longitude from
> a cell phone
>  
>
> Hi Steve,
>
> I think there are two different aspects to your question:
> 1) Accuracy of GPS Devices
> I agree with others that you can't expect a better accuracy than the 10
> to 30 feet you observed with a smartphone or a simple handheld GPS. This
> might improve by averaging, but this takes time. Survey grade GPS
> devices are very expensive. It is possible to get good modules and
> antennas as components, but building a complete GNSS system requires
> time and skill. This would reduce cost, but only to several hundred
> instead of several thousand dollars, so this is no option in your case.
> Besides, you will still need a correction data service (usually costly)
> or use two receivers (rover and base).
> So you probably have to stick with your phone, which is more flexible
> regarding the software than a handheld GPS.
>
> 2) Software
> The accuracy of the recorded position should not depend on where you tap
> the screen - a good app should allow to record the current GPS position.
> I am using Locus Map (Asamm Software) for a while now, it works quite
> well, although it does not allow position averaging. There is a free
> version, you could try that first.
>
> Regards,
> Jochen
>
> Am 22.05.20 um 20:54 schrieb Stephen Sacks:
>>
>> In order to make widely available some wise advice, I'm sending to
>> this list a message I received from Neil B.  In addition to Neil's
>> message below, I want to mention that Nicolas Cadieux also provided
>> similar information, saying I'd have to pay around $1,000 for
>> equipment that gives consistently accurate location coordinates.  And
>> thanks, also to Falk Huettmann and Bernd Vogelgesang for their replies. 
>>
>>
>> Message from Neil B:
>>
>> Hello Stephen.
>> Glad that you're having success. 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Jésahel Benoist]

For years we did surveys with a customized solution with a Starfire GPS (
https://en.m.wikipedia.org/wiki/StarFire_(navigation_system)). It needs a
subscription for best accuracy (see
https://www.navcomtech.com/en/product/globalcorrectionservice/). It was
linked to a trimble handheld data collector like this
https://geospatial.trimble.com/products-and-solutions/geo-7x that have
another integrated GPS. Pathfinder office is a great piece of software.
I have to say that it was a bit difficult to handle all of this and needs a
lot of checking and correction to have something reliable.

I think it should be possible to use a smartphone. I did some tests with Mobile
topographer which is pretty good and can be connected to an external gps
using Bluetooth/serial/usb converters and some Android dedicated apps (like
Bluetooth gps provider). But results needs to be checked, and it takes time.

The accuracy is not all. A GPS has to be fast ! Professional GPS really are
faster.

I have to say that if I had to make large surveys again, I'd prefer to rent
a professional solution. Maybe it's not cheaper but quality and saved time
is worth the price.

Jésahel
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Garth Fletcher]

The situation I was working with involved 30 points, some involving long 
hikes through the woods, spread around the periphery of a 36 square mile 
area with heavy foliage and poor or non-existent cell phone coverage. 
This precluded the use of any real-time reference base signals.
My solution thus was using a dual frequency GNSS receiver with 30+ 
minute observation times and post-processing to get to 1 meter accuracy.


However, if the problem had been one of accurately measuring points in a 
smaller area, for example an archeological site, then relative 
positioning would have been much more practical.  This would have been 
done, at lower cost and higher accuracy, with a base plus rover unit 
pair such as those described at https://emlid.com/reachrs/.  Or, if good 
internet connection was available throughout the site, possibly with a 
single rover plus connection to an external reference provider.


Regarding the question about where to locate the base unit, I would 
guess that a location with wide clear view of the sky would be the first 
priority, followed by good RF paths to all rover sites for the 
correction signals from base to rover.

--
Garth Fletcher
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Nicolas Cadieux]

Hi,

Well I don’t have much experience with the Emlid, but if you are interested, I 
can place you in contact with someone who does.  Write to me in private.  The 
important thing is to keep both units in proximity so that they both have the 
same atmospheric errors.  The advantage of the Emlid is that you can pick up 
your data for a longer period of time and then, use the base station in the 
post processing.  That will help you correct bad situation but will not fix 
every problem.   Remember the rules, BS in... BS out! 

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 20:49, j...@jmforestry.com a écrit :
> 
> ANTENNA: 
>The antenna of Garmin 64 is a lot quicker in receiving signals than that 
> of the <100$ Garmin etrex10, but it was not more precise, just a lot quicker, 
> 
> The Garmin 64 is not more precise in environments where it gets the same 
> satellites as the etrex
> In densely forested environments the Garmin 64 is more accurate. The reason, 
> to my knowledge, is that those GPS with a helix antenna can easier receive 
> satellites low on the horizon in forested areas or even can receive their 
> signals when the etrex cannot.
> J
> 
> -Original Message-
> From: Qgis-user On Behalf Of Priv.-Doz. Dr. Maria Shinoto
> Sent: Saturday, May 23, 2020 19:26
> To: Garth Fletcher 
> Cc: qgis-user@lists.osgeo.org
> Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
> phone
> 
> This discussion is interesting and very helpful. 
> 
> Some remarks from our experiences in a densely forested region with narrow 
> valleys and steep slopes, lots of water floating in creeks and abandoned rice 
> paddies -- water all around. 
> 
> 
> ANTENNA: 
> The antenna of Garmin 64 is a lot quicker in receiving signals than that of 
> the <100$ Garmin etrex10, but it was not more precise, just a lot quicker, 
> which may be due to the chips inside rather than the antenna. The Garmin 
> Oregon, which has an antenna similar to the etrex10 was a quick as the 64. We 
> did not try smartphones, but a colleague who is doing similar research told 
> us that he uses the Oregon and an iPhone with similar results. Therefore, it 
> seems that Garmin handhelds are really not necessary. 
> 
> SATELLITES:
> We receive GLONASS and GPS, max is about 18 satellites, but this gives good 
> results where the conditions are good. 
> 
> AVERAGE AND LOCATION:
> We got very good experiences with averaging. This means, I just measured 
> shortly until I got enough satellites and measured after a period of at least 
> two hours again. I repeated this on different times on other days, but after 
> all, the measurements concentrated in less than one meter, the precision of 
> the average as compared to the LiDAR data being under 40cm. 
> We had equally "precise" measurements at places beneath slopes and with lots 
> of water floating around, but the precision was in the wrong place, about 5 
> to 10 meters apart from where it should be. These are, as we were told, 
> systematical errors that cannot be overcome, by any GPS.
> 
> COMBINATION
> Solutions like the https://emlid.com/reachrs/ mentioned in this thread seem 
> to help with at lest two receivers working. Can anybody report whether it 
> helps to place the base station in a location far from the slopes and the 
> waters of the broken paddy fields or creeks and then walk around with the 
> second receiver to measure places down at the slopes?
> 
> Maria
> 
> 
> 
> 
> 
> 
>> Am 24.05.2020 um 04:51 schrieb Garth Fletcher :
>> 
>> I got involved in a project to locate the actual boundary monuments 
>> which delimit our town.  The USGS 7.5' topographic maps appeared to be 
>> in error at some locations by several hundred feet.  About 30 monument 
>> locations were involved.
>> 
>> We are in rural NH which is mostly wooded, which results in a lot of 
>> satellite signal attenuation, i.e., fewer receivable satellites.
>> 
>> I did a first effort using a Garmin eTrex 20 (~ $200) which received 
>> both the US GPS satellites and the Russian GLONASS satellites. 
>> Receiving both is important in our high attenuation environment 
>> because it significantly increases the number of receivable satellites.
>> 
>> Those measurements supported my suspicions about topo errors, but had 
>> error bounds in the tens of meters - not accurate enough for my purpose.
>> 
>> Next I used a Bad Elf Surveyor (~ $600 + Mac iPad) to record 30 
>> minutes of data into RINEX files which were then sent to CSRS-PPP for 
>> post-processing.  This somewhat reduced the error bounds, but they 
>> were still ~10 meters wide, even 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Priv.-Doz. Dr. Maria Shinoto]

ith on), your back into the 
>>>>> price range of a forestry grade survey GPS unit.  I think the Emild 
>>>>> single band gps (https://emlid.com/reachrs/ ) is probably a better choice 
>>>>> unless you really want to make this a learning project. But if I 
>>>>> understand you are really on a shoe string budget.
>>>>> 
>>>>> None of these Gps, by the way, would beat and old theodolite...  if you 
>>>>> can establish or find a good gps position (look for the city or state 
>>>>> geomatics services) or survey point,  a théodolite would give you survey 
>>>>> grade positions.  City have these points on every few blocks.  You may be 
>>>>> able to find A theodolite for free.  A second hand TotalStation could be 
>>>>> better but that will be more difficult to find in those price ranges 
>>>>> (Shoe string).  You can also rent equipment or find a college that would 
>>>>> take this up as a teaching opportunity.
>>>>> 
>>>>> Have fun!
>>>>> 
>>>>> Nicolas Cadieux
>>>>> Ça va bien aller!
>>>>> 
>>>>>> Le 23 mai 2020 à 13:52, Bernd Vogelgesang  a 
>>>>>> écrit :
>>>>>> 
>>>>>> 
>>>>>> Unfortunately, the Forest Service Website went offline (maybe this 
>>>>>> thread caused so much traffic that it broke down? ;) )
>>>>>> 
>>>>>> I'm also desperately searching for an affordable way to have at least 
>>>>>> some decent accuracy. I do not need submeter, but it would be fantastic 
>>>>>> if it was possible to achieve meter accuracy.
>>>>>> I gave up on that Garmin stuff. They might be accurate, but I have no 
>>>>>> chance to control this until I return home and put the recorded data on 
>>>>>> screen over an aerial image. Those screens are a joke, and the business 
>>>>>> logic that prevents me to put reasonable aerial imagery on the device 
>>>>>> without paying a fortune is apita. Maybe this improved cause I last 
>>>>>> checked 5 years ago.
>>>>>> 
>>>>>> Mobile phones at least in my case seem to get worse. My Motorola from 
>>>>>> 2016 had an accuracy of less than 4 meters, most of the time less than 2.
>>>>>> Now I bought a Huawei 30 pro cause of the camera (my first phone with 
>>>>>> nice pictures!), but the accuracy is a nightmare. The position is 
>>>>>> jumping around like a dog on rabies.
>>>>>> I also bought a bluetooth device (Navilock BT-821G) two years ago. This 
>>>>>> is much better than the phones GPS, tho it only receives 20 satellites 
>>>>>> maximum (The phone claims to receive some 40). But also this device 
>>>>>> sometimes, when walking a transect, is constantly 5 meters off the track 
>>>>>> for several several minutes.
>>>>>> 
>>>>>> As apps averaging the positions were mentioned: Does anyone have a 
>>>>>> recommendation on such apps (for Android)? I found some, but the 
>>>>>> usability was not that great, and some even didn't enhance anything.
>>>>>> 
>>>>>> Furthermore, I stumble upon an article about a module with u-blox chip. 
>>>>>> https://www.sparkfun.com/products/16481
>>>>>> Does anyone have any experience with modules like this and what else is 
>>>>>> needed? The description of all the stuff leaves me a bit puzzled.
>>>>>> 
>>>>>> Cheers,
>>>>>> 
>>>>>> Bernd
>>>>>> 
>>>>>> On 23.05.20 18:17, Michael.Dodd wrote:
>>>>>>> https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
>>>>>>>  I did this quite a few years ago but in the graph in supplimentary 
>>>>>>> material it shows how the accuracy of one consumer grade gps varies 
>>>>>>> over time (at a fixed point). At the time I also did a lot more 
>>>>>>> measurements using mobile phones and consumer grade units on a grid of 
>>>>>>> points in the field, that was not published but basically the phones 
>>>>>>> were often as good as if not better than the consumer grade gps units 
>>>>>>> especially when usin

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Madry, Scott]

antastic if it was 
possible to achieve meter accuracy.
I gave up on that Garmin stuff. They might be accurate, but I have no chance to 
control this until I return home and put the recorded data on screen over an 
aerial image. Those screens are a joke, and the business logic that prevents me 
to put reasonable aerial imagery on the device without paying a fortune is 
apita. Maybe this improved cause I last checked 5 years ago.

Mobile phones at least in my case seem to get worse. My Motorola from 2016 had 
an accuracy of less than 4 meters, most of the time less than 2.
Now I bought a Huawei 30 pro cause of the camera (my first phone with nice 
pictures!), but the accuracy is a nightmare. The position is jumping around 
like a dog on rabies.
I also bought a bluetooth device (Navilock BT-821G) two years ago. This is much 
better than the phones GPS, tho it only receives 20 satellites maximum (The 
phone claims to receive some 40). But also this device sometimes, when walking 
a transect, is constantly 5 meters off the track for several several minutes.

As apps averaging the positions were mentioned: Does anyone have a 
recommendation on such apps (for Android)? I found some, but the usability was 
not that great, and some even didn't enhance anything.

Furthermore, I stumble upon an article about a module with u-blox chip. 
https://www.sparkfun.com/products/16481
Does anyone have any experience with modules like this and what else is needed? 
The description of all the stuff leaves me a bit puzzled.

Cheers,

Bernd

On 23.05.20 18:17, Michael.Dodd wrote:
https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
 I did this quite a few years ago but in the graph in supplimentary material it 
shows how the accuracy of one consumer grade gps varies over time (at a fixed 
point). At the time I also did a lot more measurements using mobile phones and 
consumer grade units on a grid of points in the field, that was not published 
but basically the phones were often as good as if not better than the consumer 
grade gps units especially when using certain apps to average points.
[X]<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 - Methods 
in Ecology and Evolution - Wiley Online 
Library<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Introduction. There has been much written about sampling design, spatial scale 
and the need for permanent plots in ecological long‐term monitoring, for 
example, the paper on spatial scaling in ecology has been cited over 1500 
times, but one frequently ignored issue, intimately associated with sampling 
design, scale and permanence of plots, is how to locate positions accurately.
besjournals.onlinelibrary.wiley.com<http://besjournals.onlinelibrary.wiley.com/>


From: Qgis-user 
<mailto:qgis-user-boun...@lists.osgeo.org> 
on behalf of Nicolas Cadieux 
<mailto:nicolas.cadi...@archeotec.ca>
Sent: 23 May 2020 16:34
To: Randal Hale 
<mailto:rjh...@northrivergeographic.com>
Cc: qgis-user@lists.osgeo.org<mailto:qgis-user@lists.osgeo.org> 
<mailto:qgis-user@lists.osgeo.org>
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
phone

CAUTION: This mail comes from outside the University. Please consider this 
before opening attachments, clicking links, or acting on the content.

Hi,

This is a very interesting list. It basically confirms what I thought. Consumer 
Point and shoot deceives are all around 2-6m with no canopy. The average 
multiple positions basically give you a better idea as a gps may get lucky.  It 
would be nice to have the full methodology for this and more data (like the 
number of satellite and the position of the constellation and the gps price 
list) but it’s very interesting none the less.  I was also happy that the data 
confirms the precision of the gps Sx-Blue 11. This claims to be sub meter and 
my tests indicated that on our office unit but it’s nice to see it done 
elsewhere.  For about 2000$, this gps is pretty good. As for the rest, the 
difference between 150$ and 1000$ is probably  more a function of the options 
(like maps and screen size...) and not a question of precision. It would be 
nice to know what gps chips they are running...

Interesting thing also is that based on my reviewing the data on my phone 
(without graph or cross tabulation tables) is that the Glonas Constellation 
does not seem to help much.  Quick stats on this list would confirm this. Maybe 
this is just a figment of my imagination because there’s only so much 
information you can grad without running proper stats.

Thanks for the post.

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 09:02, Randal Hale 
> <mailto:rjh...@northrivergeographic.com> a 
> écrit :
>
> One 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[j.m]

ANTENNA: 
The antenna of Garmin 64 is a lot quicker in receiving signals than 
that of the <100$ Garmin etrex10, but it was not more precise, just a lot 
quicker, 

The Garmin 64 is not more precise in environments where it gets the same 
satellites as the etrex
 In densely forested environments the Garmin 64 is more accurate. The reason, 
to my knowledge, is that those GPS with a helix antenna can easier receive 
satellites low on the horizon in forested areas or even can receive their 
signals when the etrex cannot. 
J

-Original Message-
From: Qgis-user On Behalf Of Priv.-Doz. Dr. Maria Shinoto
Sent: Saturday, May 23, 2020 19:26
To: Garth Fletcher 
Cc: qgis-user@lists.osgeo.org
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
phone

This discussion is interesting and very helpful. 

Some remarks from our experiences in a densely forested region with narrow 
valleys and steep slopes, lots of water floating in creeks and abandoned rice 
paddies -- water all around. 


ANTENNA: 
The antenna of Garmin 64 is a lot quicker in receiving signals than that of the 
<100$ Garmin etrex10, but it was not more precise, just a lot quicker, which 
may be due to the chips inside rather than the antenna. The Garmin Oregon, 
which has an antenna similar to the etrex10 was a quick as the 64. We did not 
try smartphones, but a colleague who is doing similar research told us that he 
uses the Oregon and an iPhone with similar results. Therefore, it seems that 
Garmin handhelds are really not necessary. 

SATELLITES:
We receive GLONASS and GPS, max is about 18 satellites, but this gives good 
results where the conditions are good. 

AVERAGE AND LOCATION:
We got very good experiences with averaging. This means, I just measured 
shortly until I got enough satellites and measured after a period of at least 
two hours again. I repeated this on different times on other days, but after 
all, the measurements concentrated in less than one meter, the precision of the 
average as compared to the LiDAR data being under 40cm. 
We had equally "precise" measurements at places beneath slopes and with lots of 
water floating around, but the precision was in the wrong place, about 5 to 10 
meters apart from where it should be. These are, as we were told, systematical 
errors that cannot be overcome, by any GPS.

COMBINATION
Solutions like the https://emlid.com/reachrs/ mentioned in this thread seem to 
help with at lest two receivers working. Can anybody report whether it helps to 
place the base station in a location far from the slopes and the waters of the 
broken paddy fields or creeks and then walk around with the second receiver to 
measure places down at the slopes?

Maria






> Am 24.05.2020 um 04:51 schrieb Garth Fletcher :
> 
> I got involved in a project to locate the actual boundary monuments 
> which delimit our town.  The USGS 7.5' topographic maps appeared to be 
> in error at some locations by several hundred feet.  About 30 monument 
> locations were involved.
> 
> We are in rural NH which is mostly wooded, which results in a lot of 
> satellite signal attenuation, i.e., fewer receivable satellites.
> 
> I did a first effort using a Garmin eTrex 20 (~ $200) which received 
> both the US GPS satellites and the Russian GLONASS satellites. 
> Receiving both is important in our high attenuation environment 
> because it significantly increases the number of receivable satellites.
> 
> Those measurements supported my suspicions about topo errors, but had 
> error bounds in the tens of meters - not accurate enough for my purpose.
> 
> Next I used a Bad Elf Surveyor (~ $600 + Mac iPad) to record 30 
> minutes of data into RINEX files which were then sent to CSRS-PPP for 
> post-processing.  This somewhat reduced the error bounds, but they 
> were still ~10 meters wide, even for some 60 minute recordings.
> 
> 
> Finally I used an iGage iGS3 receiver (~ $2400) to record US GPS and 
> GLONASS satellites for at least 30 minutes each (up to 1 hour under 
> heavy foliage) into RINEX files sent for post-processing to CSRS-PPP.
> This approach finally realized the ±1 meter with 95% probability I needed.
> 
> A graph of the error ellipses for the 30 monuments as predicted by 
> CSRS-PPP post-processing, shown on a 1 foot grid, can be seen here:
> <http://www.Mason-NH.org/Specials/Mon_Ellipses_Final_1_ft_grid.jpg>
> Note that almost all are within ± 2 feet.
> 
> 
> GPS satellites broadcast on two frequencies, L1 and L5. A key 
> difference is that the hand-held Garmin units and the Bad Elf Surveyor 
> only use the
> L1 frequency whereas the iGS3 is a dual frequency receiver (L1 and L5).
> 
> One large source of errors is the variable signal propagation delays 
> in the ionosphere, which have predictable differences between the L1 
> and

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Nicolas Cadieux]

 if it was possible to achieve meter accuracy.
I gave up on that Garmin stuff. They might be accurate, but I
have no chance to control this until I return home and put the
recorded data on screen over an aerial image. Those screens are
a joke, and the business logic that prevents me to put
reasonable aerial imagery on the device without paying a
fortune is apita. Maybe this improved cause I last checked 5
years ago.

Mobile phones at least in my case seem to get worse. My
Motorola from 2016 had an accuracy of less than 4 meters, most
of the time less than 2.
Now I bought a Huawei 30 pro cause of the camera (my first
phone with nice pictures!), but the accuracy is a nightmare.
The position is jumping around like a dog on rabies.
I also bought a bluetooth device (Navilock BT-821G) two years
ago. This is much better than the phones GPS, tho it only
receives 20 satellites maximum (The phone claims to receive
some 40). But also this device sometimes, when walking a
transect, is constantly 5 meters off the track for several
several minutes.

As apps averaging the positions were mentioned: Does anyone
have a recommendation on such apps (for Android)? I found some,
but the usability was not that great, and some even didn't
enhance anything.

Furthermore, I stumble upon an article about a module with
u-blox chip. https://www.sparkfun.com/products/16481
Does anyone have any experience with modules like this and what
else is needed? The description of all the stuff leaves me a
bit puzzled.

Cheers,

Bernd

On 23.05.20 18:17, Michael.Dodd wrote:


https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
I did this quite a few years ago but in the graph in
supplimentary material it shows how the accuracy of one
consumer grade gps varies over time (at a fixed point). At the
time I also did a lot more measurements using mobile phones
and consumer grade units on a grid of points in the field,
that was not published but basically the phones were often as
good as if not better than the consumer grade gps units
especially when using certain apps to average points.

<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>

Where are my quadrats? Positional accuracy in fieldwork - Dodd
- 2011 - Methods in Ecology and Evolution - Wiley Online
Library

<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Introduction. There has been much written about sampling
design, spatial scale and the need for permanent plots in
ecological long‐term monitoring, for example, the paper on
spatial scaling in ecology has been cited over 1500 times, but
one frequently ignored issue, intimately associated with
sampling design, scale and permanence of plots, is how to
locate positions accurately.
besjournals.onlinelibrary.wiley.com
<http://besjournals.onlinelibrary.wiley.com/>



*From:* Qgis-user 
<mailto:qgis-user-boun...@lists.osgeo.org> on behalf of
Nicolas Cadieux 
<mailto:nicolas.cadi...@archeotec.ca>
*Sent:* 23 May 2020 16:34
*To:* Randal Hale 
<mailto:rjh...@northrivergeographic.com>
*Cc:* qgis-user@lists.osgeo.org
    <mailto:qgis-user@lists.osgeo.org> 
    <mailto:qgis-user@lists.osgeo.org>
*Subject:* Re: [Qgis-user] wishing for accurate
lattitude/longitude from a cell phone
CAUTION: This mail comes from outside the University. Please
consider this before opening attachments, clicking links, or
acting on the content.

Hi,

This is a very interesting list. It basically confirms what I
thought. Consumer Point and shoot deceives are all around 2-6m
with no canopy. The average multiple positions basically give
you a better idea as a gps may get lucky.  It would be nice to
have the full methodology for this and more data (like the
number of satellite and the position of the constellation and
the gps price list) but it’s very interesting none the less. 
I was also happy that the data confirms the precision of the
gps Sx-Blue 11. This claims to be sub meter and my tests
indicated that on our office unit but it’s nice to see it done
elsewhere.  For about 2000$, this gps is pretty good. As for
the rest, the difference between 150$ and 1000$ is probably 
more a function of the options (like maps and screen size...)
and not a question of precision. It would be nice to know what
gps chips they are running...

Interesting thing also is that based on my reviewing the data
on my phone (without graph or cross tabulation tables) is that
the Glonas Constellation does not seem to help much.  Quick
stats

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Michael . Dodd]

One app that claims to do a lot of what high precions gps does is 
https://play.google.com/store/apps/details?id=gr.stasta.mobiletopographer=en_GB
 It does allow averaging and shows quite a lot of what is going on, but still 
limited by the phone's antenna.  May have to take some of the accuracy figures 
it produces with a pinch of salt and remember that graph I mentioned earlier in 
this thread that shows how the errors change (direction/size) over time during 
the day.
[https://lh3.googleusercontent.com/KQTZIANk_20sZNVWJWTLQs0haOnA4hAXmLcPSwU_Adb4TPCt_jC5RowT1moahou2Jq4]<https://play.google.com/store/apps/details?id=gr.stasta.mobiletopographer=en_GB>
Mobile Topographer Free – Apps on Google 
Play<https://play.google.com/store/apps/details?id=gr.stasta.mobiletopographer=en_GB>
Your mobile Topographer! The leading tool for the professional surveyor or 
anyone who wants to mark his property, offering the best accuracy and extensive 
functionality that no other app can! *** Increase GPS accuracy using: - 
Weighted averaging (on every axis). - Map calibration. - Device calibration on 
map, or on a know point. *** Display and convert GPS geodetic to Cartesian EN 
coordinates ...
play.google.com


From: Qgis-user  on behalf of 
j.hu...@post-ist-da.de 
Sent: 23 May 2020 20:35
To: qgis-user@lists.osgeo.org 
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
phone


CAUTION: This mail comes from outside the University. Please consider this 
before opening attachments, clicking links, or acting on the content.

Hi Steve,

I think there are two different aspects to your question:
1) Accuracy of GPS Devices
I agree with others that you can't expect a better accuracy than the 10 to 30 
feet you observed with a smartphone or a simple handheld GPS. This might 
improve by averaging, but this takes time. Survey grade GPS devices are very 
expensive. It is possible to get good modules and antennas as components, but 
building a complete GNSS system requires time and skill. This would reduce 
cost, but only to several hundred instead of several thousand dollars, so this 
is no option in your case. Besides, you will still need a correction data 
service (usually costly) or use two receivers (rover and base).
So you probably have to stick with your phone, which is more flexible regarding 
the software than a handheld GPS.

2) Software
The accuracy of the recorded position should not depend on where you tap the 
screen - a good app should allow to record the current GPS position. I am using 
Locus Map (Asamm Software) for a while now, it works quite well, although it 
does not allow position averaging. There is a free version, you could try that 
first.

Regards,
Jochen

Am 22.05.20 um 20:54 schrieb Stephen Sacks:

In order to make widely available some wise advice, I'm sending to this list a 
message I received from Neil B.  In addition to Neil's message below, I want to 
mention that Nicolas Cadieux also provided similar information, saying I'd have 
to pay around $1,000 for equipment that gives consistently accurate location 
coordinates.  And thanks, also to Falk Huettmann and Bernd Vogelgesang for 
their replies.

Message from Neil B:

Hello Stephen.
Glad that you're having success. I would like to start off by saying that it is 
best to always reply to the mailing list and not directly to the person who 
submitted the email. Mailing lists work really well in that there is a pool of 
people out there who may be able to offer advice or may have an alternate 
method to solve the problem that may turn out to be a better way. On the flip 
side by maintaining the email chain through the mailing list, the follow up 
emails that provide information are stored in the archives which benefits 
anyone searching the internet to have the complete trail of information.

As far as your results they are acceptable for the device you're using. GPS in 
phones are never built to precision survey standards and there is no reason for 
them to be. If you're within 30ft of where the phone thinks you should be then 
you can easily navigate the rest of the way by visual sight. High end equipment 
to achieve sub-inch accuracy is probably in the range of thousands of dollars. 
One thing to keep in mind is there is a difference between the accuracy of a 
device and to what level of precision they display. While the app on the phone 
may display 8 decimal places of a lat/long coordinate and tell you if you have 
moved a foot, it doesn't help that the coordinate it is displaying is out +/- 
30 feet. The accuracy of a device can also be affected by the environment where 
the device is being operated. In regards to cell phones, they use multiple 
sources to determine location such as GPS, cell phone towers, and wifi points 
to perform the triangulation. Lack of line of sight to satellites, signals from 
cell towers bouncing off of surrounding buildings, or someone's wireless r

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Priv.-Doz. Dr. Maria Shinoto]

This discussion is interesting and very helpful. 

Some remarks from our experiences in a densely forested region with narrow 
valleys and steep slopes, lots of water floating in creeks and abandoned rice 
paddies -- water all around. 


ANTENNA: 
The antenna of Garmin 64 is a lot quicker in receiving signals than that of the 
<100$ Garmin etrex10, but it was not more precise, just a lot quicker, which 
may be due to the chips inside rather than the antenna. The Garmin Oregon, 
which has an antenna similar to the etrex10 was a quick as the 64. We did not 
try smartphones, but a colleague who is doing similar research told us that he 
uses the Oregon and an iPhone with similar results. Therefore, it seems that 
Garmin handhelds are really not necessary. 

SATELLITES:
We receive GLONASS and GPS, max is about 18 satellites, but this gives good 
results where the conditions are good. 

AVERAGE AND LOCATION:
We got very good experiences with averaging. This means, I just measured 
shortly until I got enough satellites and measured after a period of at least 
two hours again. I repeated this on different times on other days, but after 
all, the measurements concentrated in less than one meter, the precision of the 
average as compared to the LiDAR data being under 40cm. 
We had equally "precise" measurements at places beneath slopes and with lots of 
water floating around, but the precision was in the wrong place, about 5 to 10 
meters apart from where it should be. These are, as we were told, systematical 
errors that cannot be overcome, by any GPS.

COMBINATION
Solutions like the https://emlid.com/reachrs/ mentioned in this thread seem to 
help with at lest two receivers working. Can anybody report whether it helps to 
place the base station in a location far from the slopes and the waters of the 
broken paddy fields or creeks and then walk around with the second receiver to 
measure places down at the slopes?

Maria






> Am 24.05.2020 um 04:51 schrieb Garth Fletcher :
> 
> I got involved in a project to locate the actual boundary monuments 
> which delimit our town.  The USGS 7.5' topographic maps appeared to be 
> in error at some locations by several hundred feet.  About 30 monument 
> locations were involved.
> 
> We are in rural NH which is mostly wooded, which results in a lot of 
> satellite signal attenuation, i.e., fewer receivable satellites.
> 
> I did a first effort using a Garmin eTrex 20 (~ $200) which received 
> both the US GPS satellites and the Russian GLONASS satellites. Receiving 
> both is important in our high attenuation environment because it 
> significantly increases the number of receivable satellites.
> 
> Those measurements supported my suspicions about topo errors, but had 
> error bounds in the tens of meters - not accurate enough for my purpose.
> 
> Next I used a Bad Elf Surveyor (~ $600 + Mac iPad) to record 30 minutes 
> of data into RINEX files which were then sent to CSRS-PPP for 
> post-processing.  This somewhat reduced the error bounds, but they were 
> still ~10 meters wide, even for some 60 minute recordings.
> 
> 
> Finally I used an iGage iGS3 receiver (~ $2400) to record US GPS and 
> GLONASS satellites for at least 30 minutes each (up to 1 hour under 
> heavy foliage) into RINEX files sent for post-processing to CSRS-PPP. 
> This approach finally realized the ±1 meter with 95% probability I needed.
> 
> A graph of the error ellipses for the 30 monuments as predicted by 
> CSRS-PPP post-processing, shown on a 1 foot grid, can be seen here:
> 
> Note that almost all are within ± 2 feet.
> 
> 
> GPS satellites broadcast on two frequencies, L1 and L5. A key difference 
> is that the hand-held Garmin units and the Bad Elf Surveyor only use the 
> L1 frequency whereas the iGS3 is a dual frequency receiver (L1 and L5).
> 
> One large source of errors is the variable signal propagation delays in 
> the ionosphere, which have predictable differences between the L1 and L5 
> frequencies. Recording both signals allows a better estimation of, and 
> correction for, the ionospheric delays.
> 
> A word about post-processing.
> 
> I use the Canadian Geodetic Survey's CSRS-PPP processing because they 
> accept data from both US GPS and Russian GLONASS satellites whereas the 
> US Geodetic Survey's OPUS only accepts US GPS satellite data.  In our 
> heavily wooded environment the ability to use both constellations of 
> satellites provides a crucial boost in performance.
> 
> Post-processing services continuously record L1/L5 signals from hundreds 
> of fixed sites.  This allows them to accurately model the time-changing 
> errors in GPS signals, primarily ionospheric delays but also errors in 
> the satellite orbits and their clocks.
> 
> When RINEX data is submitted, the service can look at its 
> contemporaneous data from fixed receivers to model the errors at the 
> time and location of the RINEX recording 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Madry, Scott]

ng the positions were mentioned: Does anyone have a 
recommendation on such apps (for Android)? I found some, but the usability was 
not that great, and some even didn't enhance anything.

Furthermore, I stumble upon an article about a module with u-blox chip. 
https://www.sparkfun.com/products/16481
Does anyone have any experience with modules like this and what else is needed? 
The description of all the stuff leaves me a bit puzzled.

Cheers,

Bernd

On 23.05.20 18:17, Michael.Dodd wrote:
https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
 I did this quite a few years ago but in the graph in supplimentary material it 
shows how the accuracy of one consumer grade gps varies over time (at a fixed 
point). At the time I also did a lot more measurements using mobile phones and 
consumer grade units on a grid of points in the field, that was not published 
but basically the phones were often as good as if not better than the consumer 
grade gps units especially when using certain apps to average points.
[X]<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 - Methods 
in Ecology and Evolution - Wiley Online 
Library<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Introduction. There has been much written about sampling design, spatial scale 
and the need for permanent plots in ecological long‐term monitoring, for 
example, the paper on spatial scaling in ecology has been cited over 1500 
times, but one frequently ignored issue, intimately associated with sampling 
design, scale and permanence of plots, is how to locate positions accurately.
besjournals.onlinelibrary.wiley.com<http://besjournals.onlinelibrary.wiley.com/>


From: Qgis-user 
<mailto:qgis-user-boun...@lists.osgeo.org> 
on behalf of Nicolas Cadieux 
<mailto:nicolas.cadi...@archeotec.ca>
Sent: 23 May 2020 16:34
To: Randal Hale 
<mailto:rjh...@northrivergeographic.com>
Cc: qgis-user@lists.osgeo.org<mailto:qgis-user@lists.osgeo.org> 
<mailto:qgis-user@lists.osgeo.org>
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
phone

CAUTION: This mail comes from outside the University. Please consider this 
before opening attachments, clicking links, or acting on the content.

Hi,

This is a very interesting list. It basically confirms what I thought. Consumer 
Point and shoot deceives are all around 2-6m with no canopy. The average 
multiple positions basically give you a better idea as a gps may get lucky.  It 
would be nice to have the full methodology for this and more data (like the 
number of satellite and the position of the constellation and the gps price 
list) but it’s very interesting none the less.  I was also happy that the data 
confirms the precision of the gps Sx-Blue 11. This claims to be sub meter and 
my tests indicated that on our office unit but it’s nice to see it done 
elsewhere.  For about 2000$, this gps is pretty good. As for the rest, the 
difference between 150$ and 1000$ is probably  more a function of the options 
(like maps and screen size...) and not a question of precision. It would be 
nice to know what gps chips they are running...

Interesting thing also is that based on my reviewing the data on my phone 
(without graph or cross tabulation tables) is that the Glonas Constellation 
does not seem to help much.  Quick stats on this list would confirm this. Maybe 
this is just a figment of my imagination because there’s only so much 
information you can grad without running proper stats.

Thanks for the post.

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 09:02, Randal Hale 
> <mailto:rjh...@northrivergeographic.com> a 
> écrit :
>
> One other thing that may or may not be of use but the USDA Forest Service 
> Publishes a GPS Receiver Report that covers phones - and that's helped if 
> I've had a client go "Well I have a Apple  or a Android ". 
> At least I feel slightly better going "good enough" or "no not good enough".
>
> It should be good worldwide (but I will admit I think phones are my 'tech 
> ceiling' these days) but your mileage may vary.
>
> https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm
>
> Randy
>
>> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
>> Somehow I did not follow the discussion, but like to add some of our 
>> experience.
>>
>> We are doing field work in a remote region in the southern Japanese 
>> mountains, archaeological surveys on the ground based on LiDAR data.
>>
>> A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around 
>> a measured point, if used repeatedly at this point and the point is located 
>> in the middle of

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Michael . Dodd]

https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
 I did this quite a few years ago but in the graph in supplimentary material it 
shows how the accuracy of one consumer grade gps varies over time (at a fixed 
point). At the time I also did a lot more measurements using mobile phones and 
consumer grade units on a grid of points in the field, that was not published 
but basically the phones were often as good as if not better than the consumer 
grade gps units especially when using certain apps to average points.
[https://besjournals.onlinelibrary.wiley.com/cms/asset/1c8a8949-7fe4-48ea-beb9-01d4efee7ddf/mee3.2011.2.issue-6.cover.gif]<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 - Methods 
in Ecology and Evolution - Wiley Online 
Library<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Introduction. There has been much written about sampling design, spatial scale 
and the need for permanent plots in ecological long‐term monitoring, for 
example, the paper on spatial scaling in ecology has been cited over 1500 
times, but one frequently ignored issue, intimately associated with sampling 
design, scale and permanence of plots, is how to locate positions accurately.
besjournals.onlinelibrary.wiley.com


From: Qgis-user  on behalf of Nicolas 
Cadieux 
Sent: 23 May 2020 16:34
To: Randal Hale 
Cc: qgis-user@lists.osgeo.org 
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
phone

CAUTION: This mail comes from outside the University. Please consider this 
before opening attachments, clicking links, or acting on the content.

Hi,

This is a very interesting list. It basically confirms what I thought. Consumer 
Point and shoot deceives are all around 2-6m with no canopy. The average 
multiple positions basically give you a better idea as a gps may get lucky.  It 
would be nice to have the full methodology for this and more data (like the 
number of satellite and the position of the constellation and the gps price 
list) but it’s very interesting none the less.  I was also happy that the data 
confirms the precision of the gps Sx-Blue 11. This claims to be sub meter and 
my tests indicated that on our office unit but it’s nice to see it done 
elsewhere.  For about 2000$, this gps is pretty good. As for the rest, the 
difference between 150$ and 1000$ is probably  more a function of the options 
(like maps and screen size...) and not a question of precision. It would be 
nice to know what gps chips they are running...

Interesting thing also is that based on my reviewing the data on my phone 
(without graph or cross tabulation tables) is that the Glonas Constellation 
does not seem to help much.  Quick stats on this list would confirm this. Maybe 
this is just a figment of my imagination because there’s only so much 
information you can grad without running proper stats.

Thanks for the post.

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 09:02, Randal Hale  a écrit 
> :
>
> One other thing that may or may not be of use but the USDA Forest Service 
> Publishes a GPS Receiver Report that covers phones - and that's helped if 
> I've had a client go "Well I have a Apple  or a Android ". 
> At least I feel slightly better going "good enough" or "no not good enough".
>
> It should be good worldwide (but I will admit I think phones are my 'tech 
> ceiling' these days) but your mileage may vary.
>
> https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm
>
> Randy
>
>> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
>> Somehow I did not follow the discussion, but like to add some of our 
>> experience.
>>
>> We are doing field work in a remote region in the southern Japanese 
>> mountains, archaeological surveys on the ground based on LiDAR data.
>>
>> A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around 
>> a measured point, if used repeatedly at this point and the point is located 
>> in the middle of a valley. Even cell phones do a good enough job. As soon as 
>> we get closer to the steep slopes, the accuracy of the Garmin is less than 5 
>> to 10 meters. We can check this with the detailed LiDAR based map, and 
>> geologists told us, that even an expensive device could not be more precise 
>> under these conditions. So we decided to measure traditionally on the ground 
>> if precise measure is necessary, otherwise note the GPS data and the 
>> location as shown in the map.
>>
>> To sum up, we came to the conclusion not to spend money on an expensive GPS 
>> that may not work in the shadow of steep slopes -- or in the streets of New

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Mike Hyslop]

ial
> it shows how the accuracy of one consumer grade gps varies over time (at a
> fixed point). At the time I also did a lot more measurements using mobile
> phones and consumer grade units on a grid of points in the field, that was
> not published but basically the phones were often as good as if not better
> than the consumer grade gps units especially when using certain apps to
> average points.
>
> <https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
> Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 -
> Methods in Ecology and Evolution - Wiley Online Library
> <https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
> Introduction. There has been much written about sampling design, spatial
> scale and the need for permanent plots in ecological long‐term monitoring,
> for example, the paper on spatial scaling in ecology has been cited over
> 1500 times, but one frequently ignored issue, intimately associated with
> sampling design, scale and permanence of plots, is how to locate positions
> accurately.
> besjournals.onlinelibrary.wiley.com
>
> --
> *From:* Qgis-user 
>  on behalf of Nicolas Cadieux
>  
> *Sent:* 23 May 2020 16:34
> *To:* Randal Hale 
> 
> *Cc:* qgis-user@lists.osgeo.org 
> 
> *Subject:* Re: [Qgis-user] wishing for accurate lattitude/longitude from
> a cell phone
>
> CAUTION: This mail comes from outside the University. Please consider this
> before opening attachments, clicking links, or acting on the content.
>
> Hi,
>
> This is a very interesting list. It basically confirms what I thought.
> Consumer Point and shoot deceives are all around 2-6m with no canopy. The
> average multiple positions basically give you a better idea as a gps may
> get lucky.  It would be nice to have the full methodology for this and more
> data (like the number of satellite and the position of the constellation
> and the gps price list) but it’s very interesting none the less.  I was
> also happy that the data confirms the precision of the gps Sx-Blue 11. This
> claims to be sub meter and my tests indicated that on our office unit but
> it’s nice to see it done elsewhere.  For about 2000$, this gps is pretty
> good. As for the rest, the difference between 150$ and 1000$ is probably
> more a function of the options (like maps and screen size...) and not a
> question of precision. It would be nice to know what gps chips they are
> running...
>
> Interesting thing also is that based on my reviewing the data on my phone
> (without graph or cross tabulation tables) is that the Glonas Constellation
> does not seem to help much.  Quick stats on this list would confirm this.
> Maybe this is just a figment of my imagination because there’s only so much
> information you can grad without running proper stats.
>
> Thanks for the post.
>
> Nicolas Cadieux
> Ça va bien aller!
>
> > Le 23 mai 2020 à 09:02, Randal Hale 
>  a écrit :
> >
> > One other thing that may or may not be of use but the USDA Forest
> Service Publishes a GPS Receiver Report that covers phones - and that's
> helped if I've had a client go "Well I have a Apple  or a
> Android ". At least I feel slightly better going "good enough" or
> "no not good enough".
> >
> > It should be good worldwide (but I will admit I think phones are my
> 'tech ceiling' these days) but your mileage may vary.
> >
> > https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm
> >
> > Randy
> >
> >> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
> >> Somehow I did not follow the discussion, but like to add some of our
> experience.
> >>
> >> We are doing field work in a remote region in the southern Japanese
> mountains, archaeological surveys on the ground based on LiDAR data.
> >>
> >> A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm
> around a measured point, if used repeatedly at this point and the point is
> located in the middle of a valley. Even cell phones do a good enough job.
> As soon as we get closer to the steep slopes, the accuracy of the Garmin is
> less than 5 to 10 meters. We can check this with the detailed LiDAR based
> map, and geologists told us, that even an expensive device could not be
> more precise under these conditions. So we decided to measure traditionally
> on the ground if precise measure is necessary, otherwise note the GPS data
> and the location as shown in the map.
> >>
> >> To sum up, we came to the conclusion not to spend money on an expensive
> GPS that may not work in the shadow of steep slopes -- or i

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Garth Fletcher]

I got involved in a project to locate the actual boundary monuments 
which delimit our town.  The USGS 7.5' topographic maps appeared to be 
in error at some locations by several hundred feet.  About 30 monument 
locations were involved.


We are in rural NH which is mostly wooded, which results in a lot of 
satellite signal attenuation, i.e., fewer receivable satellites.


I did a first effort using a Garmin eTrex 20 (~ $200) which received 
both the US GPS satellites and the Russian GLONASS satellites. Receiving 
both is important in our high attenuation environment because it 
significantly increases the number of receivable satellites.


Those measurements supported my suspicions about topo errors, but had 
error bounds in the tens of meters - not accurate enough for my purpose.


Next I used a Bad Elf Surveyor (~ $600 + Mac iPad) to record 30 minutes 
of data into RINEX files which were then sent to CSRS-PPP for 
post-processing.  This somewhat reduced the error bounds, but they were 
still ~10 meters wide, even for some 60 minute recordings.



Finally I used an iGage iGS3 receiver (~ $2400) to record US GPS and 
GLONASS satellites for at least 30 minutes each (up to 1 hour under 
heavy foliage) into RINEX files sent for post-processing to CSRS-PPP. 
This approach finally realized the ±1 meter with 95% probability I needed.


A graph of the error ellipses for the 30 monuments as predicted by 
CSRS-PPP post-processing, shown on a 1 foot grid, can be seen here:


Note that almost all are within ± 2 feet.


GPS satellites broadcast on two frequencies, L1 and L5. A key difference 
is that the hand-held Garmin units and the Bad Elf Surveyor only use the 
L1 frequency whereas the iGS3 is a dual frequency receiver (L1 and L5).


One large source of errors is the variable signal propagation delays in 
the ionosphere, which have predictable differences between the L1 and L5 
frequencies. Recording both signals allows a better estimation of, and 
correction for, the ionospheric delays.


A word about post-processing.

I use the Canadian Geodetic Survey's CSRS-PPP processing because they 
accept data from both US GPS and Russian GLONASS satellites whereas the 
US Geodetic Survey's OPUS only accepts US GPS satellite data.  In our 
heavily wooded environment the ability to use both constellations of 
satellites provides a crucial boost in performance.


Post-processing services continuously record L1/L5 signals from hundreds 
of fixed sites.  This allows them to accurately model the time-changing 
errors in GPS signals, primarily ionospheric delays but also errors in 
the satellite orbits and their clocks.


When RINEX data is submitted, the service can look at its 
contemporaneous data from fixed receivers to model the errors at the 
time and location of the RINEX recording and thereby apply corrections.


CSRS-PPP offers 3 levels of correction: ultra-rapid (90 minutes), rapid 
(24 hour) and final (2 weeks).  Which is applied depends on how long you 
wait between recording the RINEX file and submitting it for post-processing.


The ultra-rapid will use the 90 minutes of data preceding the recording; 
the rapid will use 24 hours of data, and the final will use 2 weeks of 
data in calculating the corrections.  More data gives better models and 
corrections. In my experience the differences between 24 hour and 2 week 
corrections are minor compared to my ±1 m target accuracy.



A fixed + rover approach is the gold standard for accuracy.  This 
technique uses 2 receivers - one fixed for the duration and the other 
"roving" around to the various locations to be measured.  As long as the 
two stations are fairly close they will be affected identically by the 
same GPS errors which can then be cancelled out.  The cancelling can be 
done in real-time if the fixed station broadcasts its data to the rover, 
or it can be done by post-processing. Of course using two receivers 
doubles (or more) the equipment cost.--

Garth Fletcher

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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[j . huber]

e are my quadrats? Positional accuracy in fieldwork - Dodd -
>>> 2011 - Methods in Ecology and Evolution - Wiley Online Library
>>> <https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
>>> Introduction. There has been much written about sampling design,
>>> spatial scale and the need for permanent plots in ecological
>>> long‐term monitoring, for example, the paper on spatial scaling in
>>> ecology has been cited over 1500 times, but one frequently ignored
>>> issue, intimately associated with sampling design, scale and
>>> permanence of plots, is how to locate positions accurately.
>>> besjournals.onlinelibrary.wiley.com
>>>
>>>
>>> 
>>> *From:* Qgis-user  on behalf of
>>> Nicolas Cadieux 
>>> *Sent:* 23 May 2020 16:34
>>> *To:* Randal Hale 
>>> *Cc:* qgis-user@lists.osgeo.org 
>>> *Subject:* Re: [Qgis-user] wishing for accurate lattitude/longitude
>>> from a cell phone
>>>  
>>> CAUTION: This mail comes from outside the University. Please
>>> consider this before opening attachments, clicking links, or acting
>>> on the content.
>>>
>>> Hi,
>>>
>>> This is a very interesting list. It basically confirms what I
>>> thought. Consumer Point and shoot deceives are all around 2-6m with
>>> no canopy. The average multiple positions basically give you a
>>> better idea as a gps may get lucky.  It would be nice to have the
>>> full methodology for this and more data (like the number of
>>> satellite and the position of the constellation and the gps price
>>> list) but it’s very interesting none the less.  I was also happy
>>> that the data confirms the precision of the gps Sx-Blue 11. This
>>> claims to be sub meter and my tests indicated that on our office
>>> unit but it’s nice to see it done elsewhere.  For about 2000$, this
>>> gps is pretty good. As for the rest, the difference between 150$ and
>>> 1000$ is probably  more a function of the options (like maps and
>>> screen size...) and not a question of precision. It would be nice to
>>> know what gps chips they are running...
>>>
>>> Interesting thing also is that based on my reviewing the data on my
>>> phone (without graph or cross tabulation tables) is that the Glonas
>>> Constellation does not seem to help much.  Quick stats on this list
>>> would confirm this. Maybe this is just a figment of my imagination
>>> because there’s only so much information you can grad without
>>> running proper stats.
>>>
>>> Thanks for the post.
>>>
>>> Nicolas Cadieux
>>> Ça va bien aller!
>>>
>>> > Le 23 mai 2020 à 09:02, Randal Hale
>>>  a écrit :
>>> >
>>> > One other thing that may or may not be of use but the USDA Forest
>>> Service Publishes a GPS Receiver Report that covers phones - and
>>> that's helped if I've had a client go "Well I have a Apple
>>>  or a Android ". At least I feel slightly better
>>> going "good enough" or "no not good enough".
>>> >
>>> > It should be good worldwide (but I will admit I think phones are
>>> my 'tech ceiling' these days) but your mileage may vary.
>>> >
>>> > https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm
>>> >
>>> > Randy
>>> >
>>> >> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
>>> >> Somehow I did not follow the discussion, but like to add some of
>>> our experience.
>>> >>
>>> >> We are doing field work in a remote region in the southern
>>> Japanese mountains, archaeological surveys on the ground based on
>>> LiDAR data.
>>> >>
>>> >> A simple Garmin etrex10 is mostly reliable in an area of 40cm by
>>> 40cm around a measured point, if used repeatedly at this point and
>>> the point is located in the middle of a valley. Even cell phones do
>>> a good enough job. As soon as we get closer to the steep slopes, the
>>> accuracy of the Garmin is less than 5 to 10 meters. We can check
>>> this with the detailed LiDAR based map, and geologists told us, that
>>> even an expensive device could not be more precise under these
>>> conditions. So we decided to measure traditionally on the ground if
>>> precise measure is necessary, otherwise no

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[j . huber]

Hi Steve,

I think there are two different aspects to your question:
1) Accuracy of GPS Devices
I agree with others that you can't expect a better accuracy than the 10
to 30 feet you observed with a smartphone or a simple handheld GPS. This
might improve by averaging, but this takes time. Survey grade GPS
devices are very expensive. It is possible to get good modules and
antennas as components, but building a complete GNSS system requires
time and skill. This would reduce cost, but only to several hundred
instead of several thousand dollars, so this is no option in your case.
Besides, you will still need a correction data service (usually costly)
or use two receivers (rover and base).
So you probably have to stick with your phone, which is more flexible
regarding the software than a handheld GPS.

2) Software
The accuracy of the recorded position should not depend on where you tap
the screen - a good app should allow to record the current GPS position.
I am using Locus Map (Asamm Software) for a while now, it works quite
well, although it does not allow position averaging. There is a free
version, you could try that first.

Regards,
Jochen

Am 22.05.20 um 20:54 schrieb Stephen Sacks:
>
> In order to make widely available some wise advice, I'm sending to
> this list a message I received from Neil B.  In addition to Neil's
> message below, I want to mention that Nicolas Cadieux also provided
> similar information, saying I'd have to pay around $1,000 for
> equipment that gives consistently accurate location coordinates.  And
> thanks, also to Falk Huettmann and Bernd Vogelgesang for their replies. 
>
>
> Message from Neil B:
>
> Hello Stephen.
> Glad that you're having success. I would like to start off by saying
> that it is best to always reply to the mailing list and not directly
> to the person who submitted the email. Mailing lists work really well
> in that there is a pool of people out there who may be able to offer
> advice or may have an alternate method to solve the problem that may
> turn out to be a better way. On the flip side by maintaining the email
> chain through the mailing list, the follow up emails that provide
> information are stored in the archives which benefits anyone searching
> the internet to have the complete trail of information.
>
> As far as your results they are acceptable for the device you're
> using. GPS in phones are never built to precision survey standards and
> there is no reason for them to be. If you're within 30ft of where the
> phone thinks you should be then you can easily navigate the rest of
> the way by visual sight. High end equipment to achieve sub-inch
> accuracy is probably in the range of thousands of dollars. One thing
> to keep in mind is there is a difference between the accuracy of a
> device and to what level of precision they display. While the app on
> the phone may display 8 decimal places of a lat/long coordinate and
> tell you if you have moved a foot, it doesn't help that the coordinate
> it is displaying is out +/- 30 feet. The accuracy of a device can also
> be affected by the environment where the device is being operated. In
> regards to cell phones, they use multiple sources to determine
> location such as GPS, cell phone towers, and wifi points to perform
> the triangulation. Lack of line of sight to satellites, signals from
> cell towers bouncing off of surrounding buildings, or someone's
> wireless router using inaccurate position information can all affect
> the accuracy of what is being displayed on your phone.
>
> So the question is how are you determining that the coordinates are
> wrong? If you have information that you trust to be authoritative then
> adjust your points to those values and carry on. I have no advice or
> opinions on inexpensive devices that may help with a more accurate
> reading.
>
> Please do not respond directly to me. This email account is not
> actively monitored and I don't always have the time to follow up with
> the emails. All the best with your endeavours.
>
> ~Neil B.
>
> On Fri, May 15, 2020 at 7:52 PM Stephen Sacks  > wrote:
>
> Hi Neil,
>
>    With your help, I have successfully brought the corners of our
> gardens back from Pennsylvania to the Promenade here in Brooklyn
> Heights, New York.  Thank you.
>    At the risk of wearing out my welcome, I'm now asking for more
> advice.  My point features are approximately where they should be
> but not exactly, some points are just a few feet off and some are
> 10 or even 30 feet off.  I imported the data trying both EPSG 4326
> and 4269.
>    I'm now convinced that the problem is due to (1) my Google
> Pixel 3 cellphone, (2) the app I'm using ("Latitude Longitude"
> published by gps-coordinates), and  especially (3) my
> less-than-steady hands.  I capture coordinates by standing at
> spot, waiting for the blue dot to settle, and then touching the
> blue dot.  Often I 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[qgis-user]

  
  
On 5/23/2020 11:51 AM, Bernd Vogelgesang wrote:

  
  Unfortunately, the Forest Service Website went offline (maybe
this thread caused so much traffic that it broke down? ;) )
  

I've attached the spreadsheet from the link. 

   
  Furthermore, I stumble upon an article about a module with u-blox
  chip. https://www.sparkfun.com/products/16481
   Does anyone have any experience with modules like this and
what else is needed? The description of all the stuff leaves me
a bit puzzled.
  

There are some uBlox modules that can be had for under 10$US from
AliExpress. These are as barebones as you can get. They're just a
GPS receiver, nothing more. You need power, you need something to
read the output. On the other hand, if you're into experimenting
they're dirt cheap. I used on to build a  very basic data logger
using a $2 microcontroller to write to a flash card. Some of the
cheap uBlox modules can output carrier phase data so you could use
RTK to get sub-meter resolution, at least in theory. Doing this in
real-time in the field strikes me as hard, but you could collect the
data and post-process after the fact to get accurate field
positions. 
  

<>
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Nicolas Cadieux]

Hi,

I looked at the page.It looks like a neat project!  Buy time you buy a case, 
antenna... (I don’t think they come with on), your back into the price range of 
a forestry grade survey GPS unit.  I think the Emild single band gps 
(https://emlid.com/reachrs/ ) is probably a better choice unless you really 
want to make this a learning project. But if I understand you are really on a 
shoe string budget.

None of these Gps, by the way, would beat and old theodolite...  if you can 
establish or find a good gps position (look for the city or state geomatics 
services) or survey point,  a théodolite would give you survey grade positions. 
 City have these points on every few blocks.  You may be able to find A 
theodolite for free.  A second hand TotalStation could be better but that will 
be more difficult to find in those price ranges (Shoe string).  You can also 
rent equipment or find a college that would take this up as a teaching 
opportunity.

Have fun!

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 13:52, Bernd Vogelgesang  a écrit :
> 
> 
> Unfortunately, the Forest Service Website went offline (maybe this thread 
> caused so much traffic that it broke down? ;) )
> 
> I'm also desperately searching for an affordable way to have at least some 
> decent accuracy. I do not need submeter, but it would be fantastic if it was 
> possible to achieve meter accuracy.
> I gave up on that Garmin stuff. They might be accurate, but I have no chance 
> to control this until I return home and put the recorded data on screen over 
> an aerial image. Those screens are a joke, and the business logic that 
> prevents me to put reasonable aerial imagery on the device without paying a 
> fortune is apita. Maybe this improved cause I last checked 5 years ago.
> 
> Mobile phones at least in my case seem to get worse. My Motorola from 2016 
> had an accuracy of less than 4 meters, most of the time less than 2.
> Now I bought a Huawei 30 pro cause of the camera (my first phone with nice 
> pictures!), but the accuracy is a nightmare. The position is jumping around 
> like a dog on rabies.
> I also bought a bluetooth device (Navilock BT-821G) two years ago. This is 
> much better than the phones GPS, tho it only receives 20 satellites maximum 
> (The phone claims to receive some 40). But also this device sometimes, when 
> walking a transect, is constantly 5 meters off the track for several several 
> minutes.
> 
> As apps averaging the positions were mentioned: Does anyone have a 
> recommendation on such apps (for Android)? I found some, but the usability 
> was not that great, and some even didn't enhance anything.
> 
> Furthermore, I stumble upon an article about a module with u-blox chip. 
> https://www.sparkfun.com/products/16481
> Does anyone have any experience with modules like this and what else is 
> needed? The description of all the stuff leaves me a bit puzzled.
> 
> Cheers,
> 
> Bernd
> 
>> On 23.05.20 18:17, Michael.Dodd wrote:
>> https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
>>  I did this quite a few years ago but in the graph in supplimentary material 
>> it shows how the accuracy of one consumer grade gps varies over time (at a 
>> fixed point). At the time I also did a lot more measurements using mobile 
>> phones and consumer grade units on a grid of points in the field, that was 
>> not published but basically the phones were often as good as if not better 
>> than the consumer grade gps units especially when using certain apps to 
>> average points.
>> 
>> Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 - 
>> Methods in Ecology and Evolution - Wiley Online Library
>> Introduction. There has been much written about sampling design, spatial 
>> scale and the need for permanent plots in ecological long‐term monitoring, 
>> for example, the paper on spatial scaling in ecology has been cited over 
>> 1500 times, but one frequently ignored issue, intimately associated with 
>> sampling design, scale and permanence of plots, is how to locate positions 
>> accurately.
>> besjournals.onlinelibrary.wiley.com
>> 
>> From: Qgis-user  on behalf of Nicolas 
>> Cadieux 
>> Sent: 23 May 2020 16:34
>> To: Randal Hale 
>> Cc: qgis-user@lists.osgeo.org 
>> Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a 
>> cell phone
>>  
>> CAUTION: This mail comes from outside the University. Please consider this 
>> before opening attachments, clicking links, or acting on the content.
>> 
>> Hi,
>> 
>> This is a very interesting list. It basically confirms what I thought. 
>> Consumer Point and shoot deceives are a

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Bernd Vogelgesang]

Unfortunately, the Forest Service Website went offline (maybe this
thread caused so much traffic that it broke down? ;) )

I'm also desperately searching for an affordable way to have at least
some decent accuracy. I do not need submeter, but it would be fantastic
if it was possible to achieve meter accuracy.
I gave up on that Garmin stuff. They might be accurate, but I have no
chance to control this until I return home and put the recorded data on
screen over an aerial image. Those screens are a joke, and the business
logic that prevents me to put reasonable aerial imagery on the device
without paying a fortune is apita. Maybe this improved cause I last
checked 5 years ago.

Mobile phones at least in my case seem to get worse. My Motorola from
2016 had an accuracy of less than 4 meters, most of the time less than 2.
Now I bought a Huawei 30 pro cause of the camera (my first phone with
nice pictures!), but the accuracy is a nightmare. The position is
jumping around like a dog on rabies.
I also bought a bluetooth device (Navilock BT-821G) two years ago. This
is much better than the phones GPS, tho it only receives 20 satellites
maximum (The phone claims to receive some 40). But also this device
sometimes, when walking a transect, is constantly 5 meters off the track
for several several minutes.

As apps averaging the positions were mentioned: Does anyone have a
recommendation on such apps (for Android)? I found some, but the
usability was not that great, and some even didn't enhance anything.

Furthermore, I stumble upon an article about a module with u-blox chip.
https://www.sparkfun.com/products/16481
Does anyone have any experience with modules like this and what else is
needed? The description of all the stuff leaves me a bit puzzled.

Cheers,

Bernd

On 23.05.20 18:17, Michael.Dodd wrote:

https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x
I did this quite a few years ago but in the graph in supplimentary
material it shows how the accuracy of one consumer grade gps varies
over time (at a fixed point). At the time I also did a lot more
measurements using mobile phones and consumer grade units on a grid of
points in the field, that was not published but basically the phones
were often as good as if not better than the consumer grade gps units
especially when using certain apps to average points.
<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>

Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011
- Methods in Ecology and Evolution - Wiley Online Library
<https://besjournals.onlinelibrary.wiley.com/doi/full/10./j.2041-210X.2011.00118.x>
Introduction. There has been much written about sampling design,
spatial scale and the need for permanent plots in ecological long‐term
monitoring, for example, the paper on spatial scaling in ecology has
been cited over 1500 times, but one frequently ignored issue,
intimately associated with sampling design, scale and permanence of
plots, is how to locate positions accurately.
besjournals.onlinelibrary.wiley.com



*From:* Qgis-user  on behalf of
Nicolas Cadieux 
*Sent:* 23 May 2020 16:34
*To:* Randal Hale 
*Cc:* qgis-user@lists.osgeo.org 
*Subject:* Re: [Qgis-user] wishing for accurate lattitude/longitude
from a cell phone
CAUTION: This mail comes from outside the University. Please consider
this before opening attachments, clicking links, or acting on the content.

Hi,

This is a very interesting list. It basically confirms what I thought.
Consumer Point and shoot deceives are all around 2-6m with no canopy.
The average multiple positions basically give you a better idea as a
gps may get lucky.  It would be nice to have the full methodology for
this and more data (like the number of satellite and the position of
the constellation and the gps price list) but it’s very interesting
none the less.  I was also happy that the data confirms the precision
of the gps Sx-Blue 11. This claims to be sub meter and my tests
indicated that on our office unit but it’s nice to see it done
elsewhere.  For about 2000$, this gps is pretty good. As for the rest,
the difference between 150$ and 1000$ is probably  more a function of
the options (like maps and screen size...) and not a question of
precision. It would be nice to know what gps chips they are running...

Interesting thing also is that based on my reviewing the data on my
phone (without graph or cross tabulation tables) is that the Glonas
Constellation does not seem to help much.  Quick stats on this list
would confirm this. Maybe this is just a figment of my imagination
because there’s only so much information you can grad without running
proper stats.

Thanks for the post.

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 09:02, Randal Hale
 a écrit :
>
> One other thing that may or may not be of use but the USDA Forest
Service Pub

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[j.m]

Just one issue I did not see addressed so far. 
The type of antenna a GPS uses makes a big difference. In forested landscapes, 
the eTrex, for example, with its flat antenna (like a single penny) is 
noticeable worse for receiving satellite data than a Garmin 60 series with an 
antenna formed like a stack of pennies. The more obstruction to the satellite's 
direct line of sight, the larger the difference. 
Jake

-Original Message-
From: Qgis-user On Behalf Of Randal Hale
Sent: Saturday, May 23, 2020 9:03
To: qgis-user@lists.osgeo.org; maria.shin...@zaw.uni-heidelberg.de
Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell 
phone

One other thing that may or may not be of use but the USDA Forest Service 
Publishes a GPS Receiver Report that covers phones - and that's helped if I've 
had a client go "Well I have a Apple  or a Android ". At 
least I feel slightly better going "good enough" or "no not good enough".

It should be good worldwide (but I will admit I think phones are my 'tech 
ceiling' these days) but your mileage may vary.

https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm

Randy

On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
> Somehow I did not follow the discussion, but like to add some of our 
> experience.
>
> We are doing field work in a remote region in the southern Japanese 
> mountains, archaeological surveys on the ground based on LiDAR data.
>
> A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around 
> a measured point, if used repeatedly at this point and the point is located 
> in the middle of a valley. Even cell phones do a good enough job. As soon as 
> we get closer to the steep slopes, the accuracy of the Garmin is less than 5 
> to 10 meters. We can check this with the detailed LiDAR based map, and 
> geologists told us, that even an expensive device could not be more precise 
> under these conditions. So we decided to measure traditionally on the ground 
> if precise measure is necessary, otherwise note the GPS data and the location 
> as shown in the map.
>
> To sum up, we came to the conclusion not to spend money on an expensive GPS 
> that may not work in the shadow of steep slopes -- or in the streets of New 
> York. -- I appreciate any additional advice, and hope that this experience 
> can save Steve's organisation some money...
>
> Best,
> Maria
>
>
>
>> Am 23.05.2020 um 03:54 schrieb Stephen Sacks :
>>
>> In order to make widely available some wise advice, I'm sending to this list 
>> a message I received from Neil B.  In addition to Neil's message below, I 
>> want to mention that Nicolas Cadieux also provided similar information, 
>> saying I'd have to pay around $1,000 for equipment that gives consistently 
>> accurate location coordinates.  And thanks, also to Falk Huettmann and Bernd 
>> Vogelgesang for their replies.
>>
>>
>> Message from Neil B:
>>
>> Hello Stephen.
>> Glad that you're having success. I would like to start off by saying that it 
>> is best to always reply to the mailing list and not directly to the person 
>> who submitted the email. Mailing lists work really well in that there is a 
>> pool of people out there who may be able to offer advice or may have an 
>> alternate method to solve the problem that may turn out to be a better way. 
>> On the flip side by maintaining the email chain through the mailing list, 
>> the follow up emails that provide information are stored in the archives 
>> which benefits anyone searching the internet to have the complete trail of 
>> information.
>>
>> As far as your results they are acceptable for the device you're using. GPS 
>> in phones are never built to precision survey standards and there is no 
>> reason for them to be. If you're within 30ft of where the phone thinks you 
>> should be then you can easily navigate the rest of the way by visual sight. 
>> High end equipment to achieve sub-inch accuracy is probably in the range of 
>> thousands of dollars. One thing to keep in mind is there is a difference 
>> between the accuracy of a device and to what level of precision they 
>> display. While the app on the phone may display 8 decimal places of a 
>> lat/long coordinate and tell you if you have moved a foot, it doesn't help 
>> that the coordinate it is displaying is out +/- 30 feet. The accuracy of a 
>> device can also be affected by the environment where the device is being 
>> operated. In regards to cell phones, they use multiple sources to determine 
>> location such as GPS, cell phone towers, and wifi points to perform the 
>> triangulation. Lack of line of sight to satellites, signal

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Nicolas Cadieux]

Hi,

This is a very interesting list. It basically confirms what I thought. Consumer 
Point and shoot deceives are all around 2-6m with no canopy. The average 
multiple positions basically give you a better idea as a gps may get lucky.  It 
would be nice to have the full methodology for this and more data (like the 
number of satellite and the position of the constellation and the gps price 
list) but it’s very interesting none the less.  I was also happy that the data 
confirms the precision of the gps Sx-Blue 11. This claims to be sub meter and 
my tests indicated that on our office unit but it’s nice to see it done 
elsewhere.  For about 2000$, this gps is pretty good. As for the rest, the 
difference between 150$ and 1000$ is probably  more a function of the options 
(like maps and screen size...) and not a question of precision. It would be 
nice to know what gps chips they are running...

Interesting thing also is that based on my reviewing the data on my phone 
(without graph or cross tabulation tables) is that the Glonas Constellation 
does not seem to help much.  Quick stats on this list would confirm this. Maybe 
this is just a figment of my imagination because there’s only so much 
information you can grad without running proper stats.

Thanks for the post.

Nicolas Cadieux
Ça va bien aller!

> Le 23 mai 2020 à 09:02, Randal Hale  a écrit 
> :
> 
> One other thing that may or may not be of use but the USDA Forest Service 
> Publishes a GPS Receiver Report that covers phones - and that's helped if 
> I've had a client go "Well I have a Apple  or a Android ". 
> At least I feel slightly better going "good enough" or "no not good enough".
> 
> It should be good worldwide (but I will admit I think phones are my 'tech 
> ceiling' these days) but your mileage may vary.
> 
> https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm
> 
> Randy
> 
>> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:
>> Somehow I did not follow the discussion, but like to add some of our 
>> experience.
>> 
>> We are doing field work in a remote region in the southern Japanese 
>> mountains, archaeological surveys on the ground based on LiDAR data.
>> 
>> A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around 
>> a measured point, if used repeatedly at this point and the point is located 
>> in the middle of a valley. Even cell phones do a good enough job. As soon as 
>> we get closer to the steep slopes, the accuracy of the Garmin is less than 5 
>> to 10 meters. We can check this with the detailed LiDAR based map, and 
>> geologists told us, that even an expensive device could not be more precise 
>> under these conditions. So we decided to measure traditionally on the ground 
>> if precise measure is necessary, otherwise note the GPS data and the 
>> location as shown in the map.
>> 
>> To sum up, we came to the conclusion not to spend money on an expensive GPS 
>> that may not work in the shadow of steep slopes -- or in the streets of New 
>> York. -- I appreciate any additional advice, and hope that this experience 
>> can save Steve's organisation some money...
>> 
>> Best,
>> Maria
>> 
>> 
>> 
 Am 23.05.2020 um 03:54 schrieb Stephen Sacks :
>>> 
>>> In order to make widely available some wise advice, I'm sending to this 
>>> list a message I received from Neil B.  In addition to Neil's message 
>>> below, I want to mention that Nicolas Cadieux also provided similar 
>>> information, saying I'd have to pay around $1,000 for equipment that gives 
>>> consistently accurate location coordinates.  And thanks, also to Falk 
>>> Huettmann and Bernd Vogelgesang for their replies.
>>> 
>>> 
>>> Message from Neil B:
>>> 
>>> Hello Stephen.
>>> Glad that you're having su
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Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Randal Hale]

One other thing that may or may not be of use but the USDA Forest 
Service Publishes a GPS Receiver Report that covers phones - and that's 
helped if I've had a client go "Well I have a Apple  or a 
Android ". At least I feel slightly better going "good enough" or 
"no not good enough".


It should be good worldwide (but I will admit I think phones are my 
'tech ceiling' these days) but your mileage may vary.


https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm

Randy

On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote:

Somehow I did not follow the discussion, but like to add some of our experience.

We are doing field work in a remote region in the southern Japanese mountains, 
archaeological surveys on the ground based on LiDAR data.

A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around a 
measured point, if used repeatedly at this point and the point is located in 
the middle of a valley. Even cell phones do a good enough job. As soon as we 
get closer to the steep slopes, the accuracy of the Garmin is less than 5 to 10 
meters. We can check this with the detailed LiDAR based map, and geologists 
told us, that even an expensive device could not be more precise under these 
conditions. So we decided to measure traditionally on the ground if precise 
measure is necessary, otherwise note the GPS data and the location as shown in 
the map.

To sum up, we came to the conclusion not to spend money on an expensive GPS 
that may not work in the shadow of steep slopes -- or in the streets of New 
York. -- I appreciate any additional advice, and hope that this experience can 
save Steve's organisation some money...

Best,
Maria




Am 23.05.2020 um 03:54 schrieb Stephen Sacks :

In order to make widely available some wise advice, I'm sending to this list a 
message I received from Neil B.  In addition to Neil's message below, I want to 
mention that Nicolas Cadieux also provided similar information, saying I'd have 
to pay around $1,000 for equipment that gives consistently accurate location 
coordinates.  And thanks, also to Falk Huettmann and Bernd Vogelgesang for 
their replies.


Message from Neil B:

Hello Stephen.
Glad that you're having success. I would like to start off by saying that it is 
best to always reply to the mailing list and not directly to the person who 
submitted the email. Mailing lists work really well in that there is a pool of 
people out there who may be able to offer advice or may have an alternate 
method to solve the problem that may turn out to be a better way. On the flip 
side by maintaining the email chain through the mailing list, the follow up 
emails that provide information are stored in the archives which benefits 
anyone searching the internet to have the complete trail of information.

As far as your results they are acceptable for the device you're using. GPS in 
phones are never built to precision survey standards and there is no reason for 
them to be. If you're within 30ft of where the phone thinks you should be then 
you can easily navigate the rest of the way by visual sight. High end equipment 
to achieve sub-inch accuracy is probably in the range of thousands of dollars. 
One thing to keep in mind is there is a difference between the accuracy of a 
device and to what level of precision they display. While the app on the phone 
may display 8 decimal places of a lat/long coordinate and tell you if you have 
moved a foot, it doesn't help that the coordinate it is displaying is out +/- 
30 feet. The accuracy of a device can also be affected by the environment where 
the device is being operated. In regards to cell phones, they use multiple 
sources to determine location such as GPS, cell phone towers, and wifi points 
to perform the triangulation. Lack of line of sight to satellites, signals from 
cell towers bouncing off of surrounding buildings, or someone's wireless router 
using inaccurate position information can all affect the accuracy of what is 
being displayed on your phone.

So the question is how are you determining that the coordinates are wrong? If 
you have information that you trust to be authoritative then adjust your points 
to those values and carry on. I have no advice or opinions on inexpensive 
devices that may help with a more accurate reading.

Please do not respond directly to me. This email account is not actively 
monitored and I don't always have the time to follow up with the emails. All 
the best with your endeavours.

~Neil B.

On Fri, May 15, 2020 at 7:52 PM Stephen Sacks  wrote:
Hi Neil,

With your help, I have successfully brought the corners of our gardens back 
from Pennsylvania to the Promenade here in Brooklyn Heights, New York.  Thank 
you.
At the risk of wearing out my welcome, I'm now asking for more advice.  My 
point features are approximately where they should be but not exactly, some 
points are just a few feet off and some are 10 or even 30 feet off.  I imported 
the data 

Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone

[Priv.-Doz. Dr. Maria Shinoto]

Somehow I did not follow the discussion, but like to add some of our 
experience. 

We are doing field work in a remote region in the southern Japanese mountains, 
archaeological surveys on the ground based on LiDAR data. 

A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around a 
measured point, if used repeatedly at this point and the point is located in 
the middle of a valley. Even cell phones do a good enough job. As soon as we 
get closer to the steep slopes, the accuracy of the Garmin is less than 5 to 10 
meters. We can check this with the detailed LiDAR based map, and geologists 
told us, that even an expensive device could not be more precise under these 
conditions. So we decided to measure traditionally on the ground if precise 
measure is necessary, otherwise note the GPS data and the location as shown in 
the map. 

To sum up, we came to the conclusion not to spend money on an expensive GPS 
that may not work in the shadow of steep slopes -- or in the streets of New 
York. -- I appreciate any additional advice, and hope that this experience can 
save Steve's organisation some money...

Best, 
Maria



> Am 23.05.2020 um 03:54 schrieb Stephen Sacks :
> 
> In order to make widely available some wise advice, I'm sending to this list 
> a message I received from Neil B.  In addition to Neil's message below, I 
> want to mention that Nicolas Cadieux also provided similar information, 
> saying I'd have to pay around $1,000 for equipment that gives consistently 
> accurate location coordinates.  And thanks, also to Falk Huettmann and Bernd 
> Vogelgesang for their replies.  
> 
> 
> Message from Neil B:
> 
> Hello Stephen.
> Glad that you're having success. I would like to start off by saying that it 
> is best to always reply to the mailing list and not directly to the person 
> who submitted the email. Mailing lists work really well in that there is a 
> pool of people out there who may be able to offer advice or may have an 
> alternate method to solve the problem that may turn out to be a better way. 
> On the flip side by maintaining the email chain through the mailing list, the 
> follow up emails that provide information are stored in the archives which 
> benefits anyone searching the internet to have the complete trail of 
> information.
> 
> As far as your results they are acceptable for the device you're using. GPS 
> in phones are never built to precision survey standards and there is no 
> reason for them to be. If you're within 30ft of where the phone thinks you 
> should be then you can easily navigate the rest of the way by visual sight. 
> High end equipment to achieve sub-inch accuracy is probably in the range of 
> thousands of dollars. One thing to keep in mind is there is a difference 
> between the accuracy of a device and to what level of precision they display. 
> While the app on the phone may display 8 decimal places of a lat/long 
> coordinate and tell you if you have moved a foot, it doesn't help that the 
> coordinate it is displaying is out +/- 30 feet. The accuracy of a device can 
> also be affected by the environment where the device is being operated. In 
> regards to cell phones, they use multiple sources to determine location such 
> as GPS, cell phone towers, and wifi points to perform the triangulation. Lack 
> of line of sight to satellites, signals from cell towers bouncing off of 
> surrounding buildings, or someone's wireless router using inaccurate position 
> information can all affect the accuracy of what is being displayed on your 
> phone.
> 
> So the question is how are you determining that the coordinates are wrong? If 
> you have information that you trust to be authoritative then adjust your 
> points to those values and carry on. I have no advice or opinions on 
> inexpensive devices that may help with a more accurate reading.
> 
> Please do not respond directly to me. This email account is not actively 
> monitored and I don't always have the time to follow up with the emails. All 
> the best with your endeavours.
> 
> ~Neil B.
> 
> On Fri, May 15, 2020 at 7:52 PM Stephen Sacks  wrote:
> Hi Neil, 
> 
>With your help, I have successfully brought the corners of our gardens 
> back from Pennsylvania to the Promenade here in Brooklyn Heights, New York.  
> Thank you.
>At the risk of wearing out my welcome, I'm now asking for more advice.  My 
> point features are approximately where they should be but not exactly, some 
> points are just a few feet off and some are 10 or even 30 feet off.  I 
> imported the data trying both EPSG 4326 and 4269.
>I'm now convinced that the problem is due to (1) my Google Pixel 3 
> cellphone, (2) the app I'm using ("Latitude Longitude" published by 
> gps-coordinates), and  especially (3) my less-than-steady hands.  I capture 
> coordinates by standing at spot, waiting for the blue dot to settle, and then 
> touching the blue dot.  Often I don't touch the screen at exactly the right