Do you not understand how GPS works? All GPS/GLONASS satellites are in motion, while WAAS/EGNOS satellites are geo-stationary. This is why your GPSr is constantly downloading new ephemeris data, which informs the GPSr when and where each satellite will be, and is required before any position can be calculated. The WAAS/EGNOS satellites transmit correction data that allow the GPSr to calculate current position more precisely. When calculating your position on Earth, the only unknown is your position. The GPSr knows precisely where each satellite is.