Re: The GPS zero meridian club - a round up
Hi Doug: I recently got a used CSI LGBX Pro DGPS Receiver. This is a CSI long wave beacon receiver with an integrated Ashtech 12 channel GPS receiver iwth an antenna that receives both of them. The display option with the most resolution is dddmm. and it seems to be good to less than one foot without averaging. Note that the LF corrections are coming from an Earth station that's not to far from where you are receiving them. The WAAS differential corrections are for a much larger area and may not be as accurate, don't know as so far I don't have a WAAS corrected GPS. http://www.prc68.com/I/LGBXcsiDGPS.html Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Douglas Bateman wrote: Many thanks to all who, as typical of the list, sent relevant and interesting posts. I would like to comment on some as follows: IM: the confluence website - crazy but yet more fun. RM: the old civil 'degradation' of accuracy of GPS was removed many years ago. Dedicated GPS receivers are more accurate than smart phones or tablets who use the identity of their routers to give a location, although better than just a Postcode. See more below. JT: Google Earth matches the precision in that I found the WGS84 zero line to be exactly where Frank and I were making our observations. The Google Earth cursor shows incredible precision - down to hundredths of a second of arc. Centimetre accuracy? PP: chasing after ephemera (the lat/long lines are moving over long periods, even a year). Never mind, we simply move our GPS receivers to suit! FE: the 'confluence dial' in Austria. I remember it as being rather massive and to have moved it would have strained our party... TT: GPS averaging apps. Following this I bought two, more below. KK: HERESY because the WGS84 meridian has nothing to do with the sun. The satellites have large solar panels - just think of WGS84 as being solar powered! Spin-off: the dials on the zero meridian UK, France and Spain. RM: precision with free apps. All very good, and I tried an experiment with my Axxera GPS receiver and two averaging apps (GPS Averaging and Perfect Mark) on my iPad. The Axxera quotes a CEP of ±2.5 metres, but the experiment was to see if I could determine a change in longitude by placing a *1 metre rule* aligned with the latitude in a open area on my lawn. As it happens, for my latitude (51º 22' N) 1 metre corresponds to 0.001 minute of arc in longitude. The systems update every second so it was no trouble to average 100 samples for 3 sets of readings for each averaging app. For the GPS Averaging I got 0º 48.1357' and 0º 48.1367' at either end of the rule, and for the Perfect Mark 0º 48.1362' and 0º 48.1377. In other words definitely resolving a metre on the ground. I expect that repeating for another 600 readings half an hour later (all different satellites and bearings) I may have obtained higher precision still by combining both sets of data. Amazing. Thanks again for the fascinating insights. Regards, Doug PS An image of Frank King and BSS member Ian Butson recording the event of 0º 0' 0". Note the Greenwich landmarks in the background. The Greenwich meridian passes to the left of the power station chimneys. On 30/04/2014 17:37, Douglas Bateman wrote: This is a new club consisting, so far, of two members: Frank King and myself. After the successful British Sundial Society conference, the Sunday morning was allocated to tours of the Greenwich Observatory. Quite independently, Frank and I had the intention of location the WGS84 meridian, some 90m east of the Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile phone, and I had an Axxera GPS tracker linked to my iPad. The images, if the system will let them through, show 0º 0' 0". Anyone else willing to join this new exclusive club? Plenty of places to straddle the line between the north pole and the south pole. Doug (and Frank) --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 30/04/2014 17:37, Douglas Bateman wrote: This is a new club consisting, so far, of two members: Frank King and myself. After the successful British Sundial Society conference, the Sunday morning was allocated to tours of the Greenwich Observatory. Quite independently, Frank and I had the intention of location the WGS84 meridian, some 90m east of the Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile phone, and I had an Axxera GPS tracker linked to my iPad. The images, if the system will let them through, show 0º 0' 0". Anyone else willing to join this new exclusive club? Plenty of places to straddle the line between the north pole and the south pole. Doug (and Frank) I have been looking up the reviews on Android GPS apps (though many of the comments are generally applicable) and it seems that (unless you use surveying equipment, or you are in the armed forces) up to ten metres accuracy is about the best that you can expect. GPS Test for Android or GPS Status for Apple (more limited - apparently Apple releases fewer secrets to developers) seem to be recommended to see how accurate you are. I guess, when you use those, the more dots you get near the centre of the circle, the better ? Apparently you should spin the device on three axes (preferably more than once each) to get a better fix (you need to get at least 4 satellites, preferably 6-9). This seems to work for most people, much better than waving in a figure of eight motion. If you travel, wait until you're outside (away from buildings, vehicles and trees) before you try to get a fix, so that it can learn the new location more quickly. Any other hints and tips ? Here are my results (indoors, and without spinning) from a few free Android apps :- Mobiwia GPS Status & Toolbox Lat. 51°52.68' N 0°35.71' W (third decimal place changing) GPS Status Test & Fix Lat. 51.878° N 0.595° W (fourth decimal place changing) GPS Averaging Lat. 51°52.68' N 0°35.71' W (third decimal place changing) Sciencewithandroid Precision GPS 51°52'41'' N 0°35'43'' W (first decimal place changing) So it seems that you can probably get precision of 0.001° or 0.01' or 1" which seems pretty good to me for free apps. -- -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 30/04/2014 19:27, J. Tallman wrote: I wonder how well Google Earth matches up with this in terms of precision? Has anybody ever checked? Best, Jim Tallman www.spectrasundial.com www.artisanindustrials.com jtall...@artisanindustrials.com 513-253-5497 If you search for 51 28 39.8 N 0 00 00 E Google Earth marks the prime meridian in yellow, but as you pan, it moves around relative to the ground, so I don't understand what's going on there. Anyway, the zero longitude co-ordinates appear to be in wasteland, so there is ample opportunity for somebody to mark a line there. -- -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 02/05/2014 07:56, Kevin Karney wrote: Shame on you all - abandon this ill conceived club!! The Sun was not involved in the conception of WGS84. You should all be expelled from the Sundial mailing list as heretics Kevin Karney Freedom Cottage, Llandogo, Monmouth, NP25 4TP Phone 01594 539 595. Mobile 07595 024 960 Wasn't there a talk about longitude at one of the BSS Conferences ? -- -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 02/05/2014 07:56, Kevin Karney wrote: Shame on you all - abandon this ill conceived club!! The Sun was not involved in the conception of WGS84. You should all be expelled from the Sundial mailing list as heretics Kevin Karney Freedom Cottage, Llandogo, Monmouth, NP25 4TP Phone 01594 539 595. Mobile 07595 024 960 That's a good conversation stopper ! -- -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
Shame on you all - abandon this ill conceived club!! The Sun was not involved
in the conception of WGS84. You should all be expelled from the Sundial mailing
list as heretics
Kevin Karney
Freedom Cottage, Llandogo, Monmouth, NP25 4TP
Phone 01594 539 595. Mobile 07595 024 960
> On 1 May 2014, at 20:26, Thibaud Taudin Chabot wrote:
>
> There is an android app called "GPS averaging" that can average many readings
> in order to get a more realistic value of the position.
> Thibaud
>
> At 10:44 1-5-2014, Frank Evans wrote:
>> Greetings, fellow dialists,
>> Ian Maddocks asks what dials are on whole number lat/long lines.
>>> During the BSS tour of Austria in 2002 we visited a pillar dial labelled
>>> "Nieder osterreich" which claimed to be exactly at 48 deg N, 15 deg. E. It
>>> is recorded in " Austria 2002; a sundial safari. Bulletin of the British
>>> Sundial Society, 14, 3, 104-109, 2002" with the following: "But following
>>> the Royal Society's motto Nulius in verba ("don't believe a word of it")
>>> our party produced several GPS machines and the monument' position was
>>> found to be a couple of thou. out. The suggestion that there were enough of
>>> us present to shift it to the correct location was reluctantly rejected."
>>> Frank 55N 1W.
>>
>> ---
>> https://lists.uni-koeln.de/mailman/listinfo/sundial
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
There is an android app called "GPS averaging" that can average many
readings in order to get a more realistic value of the position.
Thibaud
At 10:44 1-5-2014, Frank Evans wrote:
Greetings, fellow dialists,
Ian Maddocks asks what dials are on whole number lat/long lines.
During the BSS tour of Austria in 2002 we visited a pillar dial
labelled "Nieder osterreich" which claimed to be exactly at 48 deg
N, 15 deg. E. It is recorded in " Austria 2002; a sundial safari.
Bulletin of the British Sundial Society, 14, 3, 104-109, 2002" with
the following: "But following the Royal Society's motto Nulius in
verba ("don't believe a word of it") our party produced several
GPS machines and the monument' position was found to be a couple
of thou. out. The suggestion that there were enough of us present
to shift it to the correct location was reluctantly rejected."
Frank 55N 1W.
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
Greetings, fellow dialists,
Ian Maddocks asks what dials are on whole number lat/long lines.
During the BSS tour of Austria in 2002 we visited a pillar dial
labelled "Nieder osterreich" which claimed to be exactly at 48 deg N,
15 deg. E. It is recorded in " Austria 2002; a sundial safari.
/Bulletin of the British Sundial Society, /14, 3,//104-109, 2002"with
the following: "But following the Royal Society's motto /Nulius in
verba/ ("don't believe a word of it") our party produced several GPS
machines and the monument' position was found to be a couple of thou.
out. The suggestion that there were enough of us present to shift it
to the correct location was reluctantly rejected."
Frank 55N 1W.
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 30/04/2014 20:19, Patrick Powers wrote: Hi Ian, Exactly so, and it would be interesting to see what dials there were on such a whole number list. But the snag in all this though is that the definitions have all been changed. The arrival of satellite technology brought with it a global redefinition of the whole earth's ellipsoid and in 1999 the International Reference Meridian (IRM) was decided. This is fixed but not fixed relative to a point on the earth! It currently passes something like 5.31 arcseconds east of Airy's meridian or 102.5 metres (336.3 feet) at the latitude of the Royal Observatory, Greenwich. But since 1999 and as a consequence of continental drift and plate tectonics, the IRM has shifted a few centimetres West back towards the Airy meridian. Airy will eventually be right (again!). That must surely be a time for REAL celebration? In the UK WGS84 latitudes and longitudes are changing at about 2.5 cm per year in a north-easterly direction. In 1989, the International Reference Meridian passed an estimated 102.478 m to the east of the Airy Transit Circle at Greenwich. There’s more about this here: http://www.thegreenwichmeridian.org/tgm/articles.php?article=7 So, members of the ‘Zero Meridian Club’ are chasers after ephemera. They will need to keep coming back every few years simply to catch up... Patrick A reason to continue ! -- -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
Hi Ian, Exactly so, and it would be interesting to see what dials there were on such a whole number list. But the snag in all this though is that the definitions have all been changed. The arrival of satellite technology brought with it a global redefinition of the whole earth's ellipsoid and in 1999 the International Reference Meridian (IRM) was decided. This is fixed but not fixed relative to a point on the earth! It currently passes something like 5.31 arcseconds east of Airy's meridian or 102.5 metres (336.3 feet) at the latitude of the Royal Observatory, Greenwich. But since 1999 and as a consequence of continental drift and plate tectonics, the IRM has shifted a few centimetres West back towards the Airy meridian. Airy will eventually be right (again!). That must surely be a time for REAL celebration? In the UK WGS84 latitudes and longitudes are changing at about 2.5 cm per year in a north-easterly direction. In 1989, the International Reference Meridian passed an estimated 102.478 m to the east of the Airy Transit Circle at Greenwich. There’s more about this here: http://www.thegreenwichmeridian.org/tgm/articles.php?article=7 So, members of the ‘Zero Meridian Club’ are chasers after ephemera. They will need to keep coming back every few years simply to catch up... Patrick From: Ian Maddocks Sent: Wednesday, April 30, 2014 6:14 PM To: Douglas Bateman ; Sundial list Subject: RE: The GPS zero meridian club Hi Doug Well there's already a very similar web site confluence.org/ This is for people trying to stand on points of exact degrees intersecting (according to WGS84) I have stood on two such points 54. N 2. W (on a lonely bit of moorland above Skipton, UK.It's very boggy , be careful ;-) ) and 52 N 5 E (Just next to a roundabout near Utrecht in the Netherlands). Trying to think back to my browsing of the site I don't recall any dial connections but then most of these confluences do lie the middle of nowhere . A more pertinent question might be what dials are on whole number lat / long lines (and why) Good luck with the membership drive! Ian Maddocks Chester, UK --- Original Message --- From: "Douglas Bateman" Sent: 30 April 2014 17:37 To: "Sundial list" Subject: The GPS zero meridian club This is a new club consisting, so far, of two members: Frank King and myself. After the successful British Sundial Society conference, the Sunday morning was allocated to tours of the Greenwich Observatory. Quite independently, Frank and I had the intention of location the WGS84 meridian, some 90m east of the Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile phone, and I had an Axxera GPS tracker linked to my iPad. The images, if the system will let them through, show 0º 0' 0". Anyone else willing to join this new exclusive club? Plenty of places to straddle the line between the north pole and the south pole. Doug (and Frank) --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 30/04/2014 19:33, Brooke Clarke wrote: Hi Richard: Prior to GPS each country had their own datum, but if you want GPS to truly be Global then you need a common datum. There were other datums prior to the World Geodetic System of 1984 (WGS84, http://en.wikipedia.org/wiki/WGS84#Longitudes_on_WGS_84) but it's the one that's the default in most GPS receivers. In military GPS receivers there's a choice of dozens of datums. The location of zero degrees is based on the Earth's rotation as measured by star observations that are more accurate now that we use atomic time rather than the Earth's rotation as a clock. http://www.prc68.com/I/DAGR.shtml Because of plate tectonics, i.e. most of the ground is moving all the time in three dimensions, including bed rock on mountains where telescopes have their foundations, there's really no such thing as a fixed location on Earth. When they do laser ranging to the moon one of the corrections is the elevation of the telescope at the instant when the laser is fired and at the instant when the return pulse is received. Called Earth Tides, and caused by the same forces that cause ocean tides. It's measured by a very sensitive gravity meter. http://en.wikipedia.org/wiki/Earth_tide Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Many thanks for that - and I thought corrections for sundials were bad enough :-) -- -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
Hi Richard:
Prior to GPS each country had their own datum, but if you want GPS to truly be Global then you need a common datum.
There were other datums prior to the World Geodetic System of 1984 (WGS84,
http://en.wikipedia.org/wiki/WGS84#Longitudes_on_WGS_84) but it's the one that's the default in most GPS receivers. In
military GPS receivers there's a choice of dozens of datums. The location of zero degrees is based on the Earth's
rotation as measured by star observations that are more accurate now that we use atomic time rather than the Earth's
rotation as a clock.
http://www.prc68.com/I/DAGR.shtml
Because of plate tectonics, i.e. most of the ground is moving all the time in three dimensions, including bed rock on
mountains where telescopes have their foundations, there's really no such thing as a fixed location on Earth. When they
do laser ranging to the moon one of the corrections is the elevation of the telescope at the instant when the laser is
fired and at the instant when the return pulse is received. Called Earth Tides, and caused by the same forces that
cause ocean tides. It's measured by a very sensitive gravity meter.
http://en.wikipedia.org/wiki/Earth_tide
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
rmallett wrote:
On 30/04/2014 17:37, Douglas Bateman wrote:
This is a new club consisting, so far, of two members: Frank King and myself.
After the successful British Sundial Society conference, the Sunday morning was
allocated to tours of the Greenwich Observatory. Quite independently, Frank and
I had the intention of location the WGS84 meridian, some 90m east of the
Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile
phone, and I had an Axxera GPS tracker linked to my iPad.
The images, if the system will let them through, show 0º 0' 0". Anyone else
willing to join this new exclusive club? Plenty of places to straddle the line
between the north pole and the south pole.
Doug (and Frank)
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
I would be all in favour of marking the zero meridian for the whole of its length on land, if that's the intention.
Why is the difference 90 metres ? Wikipedia says 200 metres ("102.5 metres east of its last position") at
http://en.wikipedia.org/wiki/Meridian_%28geography%29 - see also
http://en.wikipedia.org/wiki/Prime_meridian
http://wikimapia.org/3323604/Meridian-Building says :-
"Curiously, whether by accident or design, the location of the WGS84 0° meridian is marked in Greenwich by the
presence of a waste basket on the path leading more or less due east from the observatory containing the transit
telescope."
Is it the old thing about GPS receivers being deliberately inaccurate to preserve military secrets, or is it that
dedicated GPS receivers are more accurate than smart phones and tablets ? I know that Harriet James used a hand held
GPS receiver when measuring the location of my house.
--
--
Richard Mallett
Eaton Bray, Dunstable
South Beds. UK
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
I wonder how well Google Earth matches up with this in terms of precision? Has
anybody ever checked?
Best,
Jim Tallman
www.spectrasundial.com
www.artisanindustrials.com
jtall...@artisanindustrials.com
513-253-5497
On Apr 30, 2014 1:57 PM, rmallett wrote:
>
> On 30/04/2014 17:37, Douglas Bateman wrote:
>>
>> This is a new club consisting, so far, of two members: Frank King and myself.
>>
>>
>>
>> After the successful British Sundial Society conference, the Sunday morning
>> was allocated to tours of the Greenwich Observatory. Quite independently,
>> Frank and I had the intention of location the WGS84 meridian, some 90m east
>> of the Greenwich brass strip. Frank had an eTrex tracker and an app on his
>> mobile phone, and I had an Axxera GPS tracker linked to my iPad.
>>
>>
>>
>> The images, if the system will let them through, show 0º 0' 0". Anyone else
>> willing to join this new exclusive club? Plenty of places to straddle the
>> line between the north pole and the south pole.
>>
>>
>>
>> Doug (and Frank)
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> ---
>>
>> https://lists.uni-koeln.de/mailman/listinfo/sundial
>>
>>
>>
>
> I would be all in favour of marking the zero meridian for the whole of its
> length on land, if that's the intention. Why is the difference 90 metres ?
> Wikipedia says 200 metres ("102.5 metres east of its last position") at
> http://en.wikipedia.org/wiki/Meridian_%28geography%29 - see also
> http://en.wikipedia.org/wiki/Prime_meridian
>
> http://wikimapia.org/3323604/Meridian-Building says :-
>
> "Curiously, whether by accident or design, the location of the WGS84 0°
> meridian is marked in Greenwich by the presence of a waste basket on the path
> leading more or less due east from the observatory containing the transit
> telescope."
>
>
> Is it the old thing about GPS receivers being deliberately inaccurate to
> preserve military secrets, or is it that dedicated GPS receivers are more
> accurate than smart phones and tablets ? I know that Harriet James used a
> hand held GPS receiver when measuring the location of my house.
>
>
> --
>
> --
>
> Richard Mallett
>
> Eaton Bray, Dunstable
>
> South Beds. UK
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The GPS zero meridian club
On 30/04/2014 17:37, Douglas Bateman
wrote:
This is a new club consisting, so far, of two members: Frank King and myself.
After the successful British Sundial Society conference, the Sunday morning was allocated to tours of the Greenwich Observatory. Quite independently, Frank and I had the intention of location the WGS84 meridian, some 90m east of the Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile phone, and I had an Axxera GPS tracker linked to my iPad.
The images, if the system will let them through, show 0º 0' 0". Anyone else willing to join this new exclusive club? Plenty of places to straddle the line between the north pole and the south pole.
Doug (and Frank)
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
I would be all in favour of marking the zero meridian for the whole
of its length on land, if that's the intention. Why is the
difference 90 metres ? Wikipedia says 200 metres ("102.5 metres
east of its last position") at
http://en.wikipedia.org/wiki/Meridian_%28geography%29 - see also
http://en.wikipedia.org/wiki/Prime_meridian
http://wikimapia.org/3323604/Meridian-Building says :-
"Curiously, whether by accident or design, the location of the WGS84
0° meridian is marked in Greenwich by the presence of a waste basket
on the path leading more or less due east from the observatory
containing the transit telescope."
Is it the old thing about GPS receivers being deliberately
inaccurate to preserve military secrets, or is it that dedicated GPS
receivers are more accurate than smart phones and tablets ? I know
that Harriet James used a hand held GPS receiver when measuring the
location of my house.
--
--
Richard Mallett
Eaton Bray, Dunstable
South Beds. UK
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
RE: The GPS zero meridian club
Hi Doug Well there's already a very similar web site confluence.org/ This is for people trying to stand on points of exact degrees intersecting (according to WGS84) I have stood on two such points 54. N 2. W (on a lonely bit of moorland above Skipton, UK.It's very boggy , be careful ;-) ) and 52 N 5 E (Just next to a roundabout near Utrecht in the Netherlands). Trying to think back to my browsing of the site I don't recall any dial connections but then most of these confluences do lie the middle of nowhere . A more pertinent question might be what dials are on whole number lat / long lines (and why) Good luck with the membership drive! Ian Maddocks Chester, UK --- Original Message --- From: "Douglas Bateman" Sent: 30 April 2014 17:37 To: "Sundial list" Subject: The GPS zero meridian club This is a new club consisting, so far, of two members: Frank King and myself. After the successful British Sundial Society conference, the Sunday morning was allocated to tours of the Greenwich Observatory. Quite independently, Frank and I had the intention of location the WGS84 meridian, some 90m east of the Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile phone, and I had an Axxera GPS tracker linked to my iPad. The images, if the system will let them through, show 0º 0' 0". Anyone else willing to join this new exclusive club? Plenty of places to straddle the line between the north pole and the south pole. Doug (and Frank) --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
