The below quote is from the US AIM. Just looking for some information on what this correction message would actually contain.
Thought 1 wonders if the waas unit in the aircraft somehow takes this message (essentially a displacement correction dependant on lat and long), applies the lat long of the airport, and comes up with the local displacement error which is then applied to the gps position produced?
Thought 2 wonders if (as stated in the AIM) the correction message is not a distance, but includes the corrections to be applied for satellite clock errors (ie, a time correction), ehpemeris errors (ie a satellite position correction), and effects of ionosphere propagation (ie a time adjustment). The aircraft waas unit then uses these small corrections in satellite position and time, and thus calculates on it's own a more accurate position?
Is either Thought the correct one?
Thought 1 wonders if the waas unit in the aircraft somehow takes this message (essentially a displacement correction dependant on lat and long), applies the lat long of the airport, and comes up with the local displacement error which is then applied to the gps position produced?
Thought 2 wonders if (as stated in the AIM) the correction message is not a distance, but includes the corrections to be applied for satellite clock errors (ie, a time correction), ehpemeris errors (ie a satellite position correction), and effects of ionosphere propagation (ie a time adjustment). The aircraft waas unit then uses these small corrections in satellite position and time, and thus calculates on it's own a more accurate position?
Is either Thought the correct one?
3. Unlike traditional ground-based navigation aids, WAAS will cover a more extensive service area. Precisely surveyed wide-area ground reference stations (WRS) are linked to form the U.S. WAAS network. Signals from the GPS satellites are monitored by these WRSs to determine satellite clock and ephemeris corrections and to model the propagation effects of the ionosphere. Each station in the network relays the data to a wide-area master station (WMS) where the correction information is computed. A correction message is prepared and uplinked to a geostationary satellite (GEO) via a ground uplink station (GUS). The message is then broadcast on the same frequency as GPS (L1, 1575.42 MHz) to WAAS receivers within the broadcast coverage area of the WAAS GEO.