Quality of reported NACP in surveillance and broadcast services systems

The Surveillance and Broadcast Services System (SBSS) is tasked in part with fusing NAS radar surveillance data with ADS-B data in order to provide (1) Validated ADS-B reports to ATC, and (2) a complete picture of ADS-B equipped and non-equipped aircraft to participating Traffic Information Services-Broadcast (TIS-B) clients. In order to support these functions, the multi-sensor tracker (MST) within the SBS system must translate the ADS-B avionics reported NACp to a measurement covariance in order to complete the IMM-Kalman fusion process. It is important that the reported NACp, within the confines of the NACp construct, provide an accurate assessment of the position quality contained in the respective ADS-B report with respect to the reported time of applicability. This paper assesses NACp jitter position quality through analysis of more than one million ADS-B reports recently collected in the SBSS network. Characterizations are made for each NACp number for which there are sufficient data, and distinctions are made in characterizing NACp quality between UAT, 1090 ES (DO-260) and 1090 ES (DO-260A).