Re: [Talk-us] Website showing the best time to survey with GPS.

[Kevin Kenny]

On Wed, Jun 26, 2019 at 6:20 PM Eric H. Christensen via Talk-us
 wrote:
> I was told there was a website that forecasted the best times to do survey 
> work with GNSS based upon diversity of satellites in the sky, solar activity, 
> etc. Does anyone know what site this is?

Nowadays, the constellations are dense enough (particularly if you can
use GPS/GLONASS/Galileo/BaiDou) that a consumer-grade GPS receiver is
unlikely to see a difference based on satellite diversity. (It's
different, possibly, if there's a failed satellite and no on-orbit
spare, or the on-orbit spare hasn't been moved into position, and
there the sites like https://www.gnssplanning.com/ will give you
useful information.)

The GPS signal is more stable by night and in clear weather.

A bigger effect is signal absorption.  There's one trail near me for
which my mapping involves considerable guesswork, because there's
dense coniferous tree coverage (nothing viisible even in winter
aerials), and the trail goes down into a couple of itty-bitty slot
canyons where all the sky that the receiver can see is directly
overhead, and a little patch to the north where the satellites seldom
cross. There are also cliff faces that set up nice reflections of the
RF signal, so sometimes the receiver's computed position is false.
It's pretty wonky. I bet I could control the effects by using a
survey-grade GPS receiver, setting it on a solid tripod, and giving it
an hour or two of integration time, but I don't have such a device,
nor do I have the time to do that for each trackpoint.

Space weather is another significant effect, but right now we're close
to sunspot minimum, and space weather is mostly quiet.
https://www.swpc.noaa.gov/ provides forecasts.
https://www.swpc.noaa.gov/products/alerts-watches-and-warnings alerts
to significant conditions.
https://www.swpc.noaa.gov/impacts/space-weather-and-gps-systems gives
an idea what to look for, and
https://www.gps.gov/cgsic/meetings/2012/comberiate.pdf is a more
advanced discussion of the same thing. The bottom line here for the
Lower 48 + Hawai`i is probably 'don't worry about it unless Kp gets
above about 5 or there's a class M or X flare in progress.'

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Re: [Talk-us] Website showing the best time to survey with GPS.

[Eric H. Christensen via Talk-us]

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‐‐‐ Original Message ‐‐‐
On Thursday, June 27, 2019 7:58 AM, Simon Poole  wrote:

> The answer the OP was looking for is likely https://www.gnssplanning.com/


Thank you!!!  My Google-fu has been failing me lately.

Eric
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Re: [Talk-us] Website showing the best time to survey with GPS.

[Ian Dees]

Also take a look at http://satpredictor2.deere.com/lookup, found by
searching Google for "when is the best time for gps", which lead me to this
interesting set of StackOverflow answers:
https://gis.stackexchange.com/questions/181/is-gps-more-accurate-on-specific-hours-of-the-day,
too.

On Wed, Jun 26, 2019 at 5:20 PM Eric H. Christensen via Talk-us <
talk-us@openstreetmap.org> wrote:

> I was told there was a website that forecasted the best times to do survey
> work with GNSS based upon diversity of satellites in the sky, solar
> activity, etc. Does anyone know what site this is?
>
> Thanks,
> Eric
>
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Re: [Talk-us] Website showing the best time to survey with GPS.

[Simon Poole]

The answer the OP was looking for is likely https://www.gnssplanning.com/




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Re: [Talk-us] Website showing the best time to survey with GPS.

[Eric H. Christensen via Talk-us]

I use GPSr devices other than what's in my smartphone.  The point is that if 
all the satellites are clustered directly overhead the diversity isn't great 
enough to give a truly accurate position on the ground.  For best surveying 
with a GPSr, you want satellites to not only be overhead but toward the horizon 
(and everywhere in between) as well.

Eric

‐‐‐ Original Message ‐‐‐
On Thursday, June 27, 2019 2:15 AM, Mateusz Konieczny  
wrote:

> Note that for a typical GPS, especially GPS in smartphone I would expect that
> this effects will be not really noticeable in affecting accuracy.
>
> Maybe except massive solar storms like
> https://en.wikipedia.org/wiki/Solar_storm_of_1859
>
> I tried to check sources, but quick search found nothing really good, except 
> some things
> like
> https://www.utdallas.edu/news/2013/5/16-23761_Solar-Flares-May-Interrupt-GPS-Navigation-Research_article-wide.html
> "If a flare is particularly large, the resulting turbulence in our upper 
> atmosphere
> could disrupt radio signals and GPS navigation, for example."
>
> what seems to confirm that you need really unusual activity to have results.
>
> 27 Jun 2019, 00:18 by talk-us@openstreetmap.org:
>
>> I was told there was a website that forecasted the best times to do survey 
>> work with GNSS based upon diversity of satellites in the sky, solar 
>> activity, etc. Does anyone know what site this is?
>>
>> Thanks,
>> Eric___
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[Talk-us] Careful, "st" can mean "stone" in some places | Re: Typical maxweight signs in USA? (editor developmnent question)

[Rory McCann]

On 25/06/2019 20:01, Mateusz Konieczny wrote:

25 Jun 2019, 17:47 by pe...@dobratz.us:

Reading this page, I see the potential ambiguity extends deeper than
I realized (short ton, metric ton, long ton)
https://en.wikipedia.org/wiki/Tonne


AFAIK all cases of "t" in USA on max weight signs means "short ton".

Taggable by adding "st" unit or by converting to pounds, and adding 
"lbs" unit.
First seems to be superior as puts lower burden on mappers and it allows 
to directly map what is signed.

See https://wiki.openstreetmap.org/wiki/Key:maxweight#Usage


FYI "st" is used in Britain & Ireland to mean a "stone" ( 14 pounds i.e. 
6.35029318 kg ). People in UK & Ireland can refer to their weight as "X 
stone", or "I've lost half a stone on my diet" (but kg is common too).


If you use "st" in an OSM tag value for weight, a not very bright data 
consumer might interpret that as stone. Maybe we can side-step that 
problem by picking a better suffix?


What about "uston" (maxweight=8 uston)?

Are there other regions which use “ton/tonne/...” on signs which 
*aren't* the US ton? If so, we could just say “t” means “us short ton”.


“Gallons” is also different in US units & imperial units, so "usgal" or 
"impgal" are better choices than "gal". (Relevant when mapping fire 
hydrant flow rates).


https://en.wikipedia.org/wiki/Stone_(unit)


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Re: [Talk-us] Website showing the best time to survey with GPS.

[Mateusz Konieczny]

Note that for a typical GPS, especially GPS in smartphone I would expect that
this effects will be not really noticeable in affecting accuracy.

Maybe except massive solar storms like
https://en.wikipedia.org/wiki/Solar_storm_of_1859

I tried to check sources, but quick search found nothing really good, except 
some things
like
https://www.utdallas.edu/news/2013/5/16-23761_Solar-Flares-May-Interrupt-GPS-Navigation-Research_article-wide.html
 

"If a flare is particularly large, the resulting turbulence in our upper 
atmosphere 
could disrupt radio signals and GPS navigation, for example."

what seems to confirm that you need really unusual activity to have results.


27 Jun 2019, 00:18 by talk-us@openstreetmap.org:

> I was told there was a website that forecasted the best times to do survey 
> work with GNSS based upon diversity of satellites in the sky, solar activity, 
> etc.  Does anyone know what site this is?
>
> Thanks,
> Eric
>
>
>
>
>
>

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