Comparison of ADS-B Verification Methods: Direct TDOA and MLAT

Abstract

Automatic Dependent Surveillance—Broadcast (ADS-B) is an emerging means of aeronautical surveillance for air traffic control. Aircraft periodically broadcast positional updates to ground stations. Although ADS-B outperforms traditional radars in terms of accuracy and update rate, positional verification—a technique used to check the validity of the position report—is necessary to counter anomalies. In this study, two different methods were compared when the ground stations measure time difference of arrival (TDOA). One is direct; the test statistic is essentially the difference between the measurement and a prediction calculated from the position report. Another method is multilateration (MLAT)-based and two-step; the emitter position is firstly estimated, whereupon the difference between the estimated and reported positions constitutes the test statistic. As a result of the comparison, a performance difference, which depending on the number of receivers, was revealed. This is an useful suggestion for implementing ADS-B when the existing multilateration infrastructure is exploited.

Keywords

• Automatic dependent surveillance—broadcast (ADS-B)
• multilateration (MLAT)
• time difference of arrival (TDOA)