Performance assessment of GPS augmentation systems

GPS augmentation systems such as the Wide-Area Augmentation System (WAAS) require independent performance evaluation. ISTI has developed the Performance Assessment System (PAS) for the FAA to independently monitor and evaluate the performance of the WAAS. The PAS uses National Satellite Test Bed (NSTB) receiver output, plus other sources of independent data, to calculate WAAS-compliant user position solutions. Accuracy and integrity performance is determined in near real-time from user position solutions distributed throughout the WAAS service volume. PAS is currently being enhanced to include near real-time ionospheric displays including a total electron content (TEC) map and independent evaluation of the ionospheric correction and the grid ionospheric vertical error (GIVE). The PAS is implemented as an n-tier, client-server, distributed software application using the Internet, Java, and the common object request brokering architecture (CORBA) as the core implementation technologies to make PAS capabilities available over the World Wide Web