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Sunnyvale, CA | In an earlier post
http://talk.newagtalk.com/forums/thread-view.asp?tid=21187&mid=1447...
I stated the time constant for WAAS ionosphere corrections was 6 hours. I wish to make a correction to this statement. The maximum update interval for the WAAS ionosphere data is 5 minutes, which means that WAAS ionosphere corrections will improve greatly a non-DGPS position which uses the broadcast ionosphere model with a much longer time constant, which is on the order of 6 hours. Because of the effects of sunspots on the ionosphere, the error of GPS will vary over the 11 year sunspot cycle. We are near the minimum of the sunspot cycle allowing GPS to perform very well compared to how it will perform when the sunspots start increasing in a few years. For more information about sunspots you can look at the web site http://www.spaceweather.com/
When the sunspots do increase, one of the strategies for better GPS performance will be the use of dual frequency receivers which will allow a direct measurement of the delay caused by the ionosphere or the use of nearby beacon reference stations. | |
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correction on an earlier post about WAAS
