Algorithm for Three-Dimensional Geodetic Positioning Based on Measurements of Automatic Dependent Surveillance-Broadcast Signals

摘要

This paper develops a non-precision geolocation algorithm for airborne vehicles that can serve as a redundant navigation system for use during locally limited GNSS availability, can be used to validate on-board satellite navigation systems to detect local spoofing attempts, and can be used to validate Automatic Dependent Surveillance - Broadcast (ADS-B) position reports. The algorithm utilizes the proliferation of ADS-B equipped aircraft as airborne navigation aids in an RF angle of-arrival (AOA) and angle-of-elevation (AOE) based geodetic positioning algorithm. With multiple GNSS quality navigation aids available, mean horizontal position errors are observed to be less than 500 meters and the mean vertical position error is less than 10 meters. However, as expected, the quality of the navigation aids has an effect on the accuracy of the algorithm. As the quality and number of navigation aids decrease, so too does the accuracy of the algorithm. However, even under a worst-case scenario, the algorithm provides reasonable estimates that can provide a lateral position estimate within 3.7NM and an altitude estimate within 497 meters (95% containment). Perhaps more significantly, the improved algorithm is also capable of validating reported ADS-B altitude of equipped aircraft and is a perfect candidate for coupling with an INS or simply adding a barometric altimeter measurement to aid the vertical position estimate. This work presents a non-precision means of determining an airborne vehicle's geodetic position, even in the absence of GNSS. In addition, this algorithm can be used to validate GNSS position reports in a GNSS spoofed environment and can serve as a means to validate ADS-B position reports from suitably equipped aircraft operating in proximity to the host vehicle.