System integrity and track accuracy methodology for traffic information service-broadcast (TIS-B)

Abstract

Safe Flight 21 (SF 21) is a joint effort by the government and industry to improve the safety, efficiency, and capacity of the National Airspace System (NAS). SF 21 is exploring the use of automatic dependent surveillance-broadcast (ADS-B), broadcast services, and related enabling technologies to provide common, real-time traffic information to both air traffic controllers and flight crews. One of the deliverables based on R. L. Bourgeois and F. R. Castella (2003) for The Johns Hopkins University Applied Physics Laboratory (JHU/APL) under the Federal Aviation Administration (FAA) Contract DTFA01-02-C-00046 is a report defining computations for the system quality and integrity parameters; navigation accuracy category (NAC), navigation integrity category (NIC), and surveillance integrity level (SIL) for the traffic information service-broadcast (TIS-B) capability being proposed for the NAS. The ADS-B system messages contain fields (NAC, NIC, and SIL) to report the quality of the aircraft position and velocity estimates. For the ADS-B system the values for these fields are derived from the global positioning system (GPS) using information about the GPS constellation, available satellites, etc. The computations are then mapped into the quantized values to be transmitted. The TIS-B system forms target position and velocity estimates from radar reports. The algorithms used within the GPS system to compute the NIC and SIL values are not directly applicable to the TIS-B system. This report presents a methodology to compute the integrity parameters for the TIS-B target report messages.