Differential GPS ground station

The ground system improves the aircraft positional accuracy by recording 1-sample-per-second raw gps pseudorange, carrier phase, and carrier doppler frequency data (RANGECMP log) at a fixed and known location for use in post-flight processing. It is largely obsolete since the OmniSTAR / TerraStar correction real-time corrections services have been used, but may still be useful in locations such as high latitudes where the real-time corrections are difficult to receive.