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WAAS Changes?
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Doug S
Posted 4/17/2006 10:52 (#5889 - in reply to #5865)
Subject: RE: WAAS Changes?


Gentlemen,

Excellent discussion on WAAS. Up here in the Northern Canadian grain belt the WAAS changes are very welcome for my producers. We used to find AOR-W at an azimuth of 120 and an elevation on 10 degrees. That is the only WAAS source that we could access so needless to say that using WAAS in ag. was a bit of a challenge. It has been very interesting to watch AOR-W move to it's new position, azimuth 220 @ 22 degrees. I do a lot of developmental work and signal testing here for various companies, as this is the "black hole" of ag GPS in North America. One company sent me their latest beta software 2 weeks ago and said, i"f if will run up there we'll release it". When the new WAAS signals are fully implemented I have calculated an elevation of 28 degrees here, and with the increased power, we should be in good shape as far as signal aquisition.

The problem in Canada is the WAAS correction itself. The extrapolations that need to be applied to the ionospheric model broadcast with WAAS does not always match with reality here. According to one of the GPS engineers I test for, in one test last week, of the 7 sats being used in the solution, 5 did not have a valid ionospheric model in the correction. Tough to work with that. There is a new WAAS refernece station being set up at Winnipeg, which will help Manitoba users, and perhaps help the rest of us because of it's latitude.

I have done extensive testing this winter on the new CDGPS differential correction that has been developed for western Canada, and the results have been very promising. Excellent signal, and very good corrections. I am showing static accuracies equal to or slightly better than WAAS when the sky is "good", and much superior performance when the sky has it's challenges. For those followers of this forum in western Canada, (and there are many!) check out the CDGPS signal. It may be the answer until the WAAS network is fully implemented. The CDGPS weathered the geomagnetic storm this past friday much better than the WAAS did. There are a few receivers that have CDGPS capabilities built in. They are costly, but they are also dual freq. receivers. You can also purchase "add ons" to use the CDGPS with a wider variety of receivers.
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