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xander Occasional Visitor
Joined: Jun 16, 2005 Posts: 32
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Posted: Fri Jun 17, 2005 11:00 pm Post subject: WAAS in UK? |
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Is there any advantage of using WAAS setting in the UK (and Europe)? Improved accuracy over here? WAAS seems to be an American only standard http://www.garmin.com/aboutGPS/waas.html , but is it compatable with our EGNOS? |
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Tinker15 Occasional Visitor
Joined: Jun 11, 2005 Posts: 2
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Skippy Pocket GPS Verifier
Joined: 24/06/2003 00:22:12 Posts: 2946 Location: Escaped to the Antipodies! 36.83°S 174.75°E
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Posted: Fri Jun 17, 2005 11:55 pm Post subject: |
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WAAS, EGNOS, MSAS etc are collectively known as Space Based Augmentation Systems (SBAS) and they are compatible with each other. Garmin should probably call it SBAS rather than WAAS.
EGNOS is running in test mode - it has been for quite a while now and is over a year late for it's "go live" date.
You can pick up the signals by switching WAAS on and looking for sats 33, 39 or 44 on your Garmin. You have to have a good view of the sky for about 15 minutes before it gets enough data for a "3D Differential Fix" and you get the D symbol against all the sats. The GPS claims that it's accuracy improves to about 2 meters but I haven't independantly verify this against a surveyed location.
When WAAS is on the GPS uses more processing power than with it off so you may see the map redraw happen a bit slower.
Enjoy! _________________ Gone fishing! |
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DPL Regular Visitor
Joined: Dec 09, 2004 Posts: 127 Location: Coventry
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Posted: Sat Jun 18, 2005 3:33 pm Post subject: |
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Skippy wrote: | ...You can pick up the signals by switching WAAS on... |
Skippy
Tried this and...nothing. Using an external antenna for best reception there were five satellites acquired and the accuracy was posted at 20 feet. After enabling WAAS for an hour the same five sats were up but accuracy was 31 feet.
Sats 33, 39 or 44 were not acquired or listed _________________ Garmin C320 & Garmin Quest |
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DPL Regular Visitor
Joined: Dec 09, 2004 Posts: 127 Location: Coventry
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Posted: Sun Jun 19, 2005 3:09 pm Post subject: |
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Different result today...7 sats acquired and GPS screen showed "3D differentiation" and accuracy of 7 feet. The whole process took around 30 secs. Sat 33 was listed, but no 39 or 44. Individual sat bars had a 'D' or 'O' in them (hard to tell which) that seemingly came and went with no discernible pattern. _________________ Garmin C320 & Garmin Quest |
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Skippy Pocket GPS Verifier
Joined: 24/06/2003 00:22:12 Posts: 2946 Location: Escaped to the Antipodies! 36.83°S 174.75°E
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Posted: Sun Jun 19, 2005 10:54 pm Post subject: |
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DPL wrote: | Different result today...7 sats acquired and GPS screen showed "3D differentiation" and accuracy of 7 feet. The whole process took around 30 secs. Sat 33 was listed, but no 39 or 44. |
Wow, that's quick.
The WAAS satelites are numbered 33 to 51. In the UK I usually see 33, 39 and 44.
In London, I see 39 in the South East and 44 is East South East (quite low in the sky so hard to "see" sometimes). I'm not convinced that 39 is transmitting any useful information though because my Quest sees it then switches back to 33 after a little while.
The symbol is a D and means "Differential". The correction data is transmitted seperately for all the satelites so you might have a D for some but not for others.
The Quest can lock onto 12 sats, with WAAS on it reserves two slots for the 33-51 WAAS sats. Initially, it cycles through all the possible numbers until it picks one up. Once it has had a fix for a while then it seems to settle on 44 and cycle between 33 and 39.
I don't think 39 gives any useful information, my Quest sees it then moves on to searching for 33 again. _________________ Gone fishing! |
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DPL Regular Visitor
Joined: Dec 09, 2004 Posts: 127 Location: Coventry
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Posted: Mon Jun 20, 2005 8:41 pm Post subject: |
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Skippy wrote: | Wow that's quick... |
Probably because I'm running a Garmin external antenna on the car roof Acquisition of sats has always been quick when this is connected (£70 or so and it gets my recommendation). The Quest antenna takes about 30secs to acquire on a good day (not tried it with WAAS on though), up to 3 minutes if there's dense cloud cover. (Unit is RAM mounted on the dash top of a Ford Focus C-Max with heated screen)
Still only saw up to sat 33 today...and plenty of 'D's. Accuracy was 7 feet 8) The technology's impressive but a bit academic really - with road lock on I can't envisage any performance gain for car/road use _________________ Garmin C320 & Garmin Quest |
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