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Cedar Rapids, Iowa | The WAAS test was done last August on firmware v3.57. Obviously the atmospheric conditions are going to have changed a lot since then. I do not know which satellite the correction data was coming from, but I thought the WAAS data is now the same from both satellites?
I've been told that SF1 is a dual frequency correction, although I haven't seen any official word of that being true or not. If so, that could be why SF2 is more stable than WAAS.
Translation: On WAAS, the reported position was within 30 inches of the "center" position, 99.7% of the time over 24 hours. On a shorter time scale such as pass-to-pass, it will have a lot less drift.
I've also read told that WAAS was created for aviation primarily as a method of feedback to know if the GPS data is good. The accuracy improvement wasn't the primary focus. Instrument landings usually use a set of radio transmitters, one one each side of the runway, running on different frequencies. The airplane has a receiver that can figure out where the plane is relative to the center line of the runway. Thus GPS and WAAS are used once airborn, but usually other methods are used for assisted landings.
-Lance | |
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Static Accuracy Testing of SF1
