Surveillance accuracy analysis of ADS-B supporting the separation service in western China

Currently, the Civil Aviation Administration of China (CAAC) is developing a promising new surveillance technology Automatic Dependent Surveillance-Broadcast (ADS-B) in western China, with the aim of resolving the lack of surveillance methods there caused by the complex terrain and costly maintenance. By virtue of ADS-B technology, more timely, accuracy and abundant information about aircraft could be provided. Consequently, the separation service may potentially be more feasible and efficient, which means the minimum safe-separation distance between aircraft could be achieved more credibly and thus the airspace capacity would be increased. However, because the traditional separation standards are developed only for radar, it cannot be straightly utilized by ADS-B technology. In this paper, the latest progress of ADS-B development in western China is introduced. Then the measured position accuracy is considered for evaluation of ADS-B performance. In virtue of these methods, real flight test data from Chengdu to Jiuzhai was collected and used to analyze the accuracy quality to support the separation service in western China. During the validation flight tests, the true locations of the aircraft are determined by onboard real-time kinematic (RTK) receiver. The downlink ADS-B position reports are used to verify the ADS- B error model and calculate the separation error. For the measured position accuracy, an assessment method is proposed to compare ADS-B with radar data, and ADS-B is proven to provide accuracy performance equal to or better than traditional radar. For the separation position accuracy, the separation between two waypoints is estimated and compared with the RTK baseline data. Sometimes the two points may be tracked by different sensors and thus the errors caused by asynchronous updates should be unified, which is solved by extrapolation algorithms. According to the ADS-B accuracy analysis results and required surveillance accuracy of radar in support of separation service, ADS-B surveillance method is capable enough to accommodate the separation service of radar.