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ADS-B message contents evaluation and breakdown of anomalies

Automatic Dependent Surveillance Broadcast (ADS-B) data from the Grand Forks International Airport ground receiver was explored in this investigation. The results highlight some anomalies in the message contents including partial message loss, drop out, altitude discrepancy. The ADS-B payload data frame contains the aircraft position (latitude, longitude), altitude, aircraft status (ground/air), quality indicators as well as a few other pieces of information. These are important navigation information, which are crucial for separation and collision avoidance. Our primary assessment reveals that the message contents were sometimes inconsistent from nominal conditions. This study took the raw archived binary data sets, and converted to a readable format. An exploratory analysis was conducted where several unusual characteristics were identified. Drop outs were spotted, which implies that the ADS-B update period exceeds one second. There are cases of partial message content losses and some data showed drift from the nominal value. Discrepancies between geometric and barometric altitude were also noticed. Introducing unmanned aircraft to National Airspace (NAS) will significantly increase the volume of traffic. Therefore, prior to the complete implementation of ADS-B, it is important to address, understand and monitor these deficiencies. This will help to improve system performance to design assurance levels appropriate for both manned and unmanned aircraft.