Research Of Optimization Theory Of RAIM Prediction

Performance-based navigation (PBN) combines modern communication, navigation and surveillance technology to give full play to the performance of the aircraft and provide accurate flight guidance for all flight phases, which from departure to approach. Compared with traditional flight mode, which based on terrestrial radio navigation system, PBN operation uses Global Navigation Satellite System (GNSS) as the primary source of navigation and gives strict requirement on the accuracy, integrity, continuity and availability. Receiver Autonomous Integrity Monitoring (RAIM) is a kind of technique for integrity monitoring of GNSS using redundant information of satellites, it has been widely used because of the rapid testing speed and without any auxiliary. However, the number of visible satellite and their geometrical distribution will affect the credibility of monitoring results of RAIM technique and even make it unavailable, which is the safety risk. RAIM prediction is used to analyze the number of visible satellite and their geometrical distribution to estimate its suitability for integrity monitoring according to the performance requirements. The FAA, CAAC and ICAO issues some relevant advisory circulars, which require airlines must do RAIM availability prediction before planes take off when GNSS is used for civil aviation flight operations.Firstly, this paper introduced PBN operation and GNSS, expound the advantages and requirements of the application of GNSS in civil aviation. Secondly, combined with the related domestic and foreign technical standards, the paper analyzed RAIM algorithm and RAIM prediction algorithm, proposed some improvement and optimization based on the traditional RAIM prediction. Again, the RAIM prediction derivation of each module were presented; Building a large elliptical course model based on the WGS-84ellipsoid and speculating the four-dimensional position information of aircraft according to the flight plan; combined with Google Earth terrain database, the paper calculated the terrain mask angle by extracting elevation data through traversing terrain and accessed it as the basis for the decision of visible satellites. Finally, the optimized algorithm of RAIM prediction were realized completely using MATLAB software and some simulations for an airport’NPA, a PBN route and a RNP approach were given and discussed, the simulation results verified the effectiveness of the optimized algorithm.