Talk:Differential GPS

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[edit] WAAS not technically a DGPS

I removed / modified the following text from the article, but worry my edit is incomplete

The term can refer both to the generalized technique, as well as specific implementations using it. For instance, the FAA's WAAS system uses differential techniques to improve accuracy, broadcasting the corrections via L band satellite transmissions. Other examples of similar systems include the European Geostationary Navigation Overlay Service, Japan's Multi-Functional Satellite Augmentation System, Canada's CDGPS and the commercial VERIPOS, StarFire and OmniSTAR systems.

Technically, WAAS is not a Differential GPS system; it actually transmits updates regarding the GPS satellites themselves plus environmental delays, which is taken into account during the calculation process. This is different from DGPS which provides a "total error offset" or a "position error" which is simply added back into the local receiver's final calculated position. While the result (improved accuracy) is similar to DGPS, its a fundamental different process.

I am unsure about how the other systems operate, and so the reformatted text includes them, but this may need to be updated in the future. For instance, I believe the EGNOS is identical to WAAS, but am unsure how StarFire and OmniSTAR work. - Davandron | Talk 21:41, 14 December 2006 (UTC)