Research on GPS Receiver Autonomous Integrity Monitoring Based on Parity Space Algorithm

Abstract

While GPS can unquestionably provide the accuracy position for such demanding real-time applications as aircraft precision approach and landing. In order to make the navigation system operate continuously without performance degradation, it is important to detect and exclude faults that cause the accuracy and integrity risks. Receiver Autonomous Integrity Monitoring (RAIM) methods on GPS have become a focus of research in recent years. RAIM includes fault detection and fault isolation. Fault detection requires at least one redundant measurement. Fault isolation requires at least two redundant measurements. In the paper, based on the parity space RAIM algorithm is given for fault detect and isolation. According to the different distribution of test statistic's probability density function (PDF) in normal and failure conditions, RAIM was analyzed in statistical aspect in detail. In order to decide whether or not the corresponding navigation measurement will exist fault, the test statistic value is compared to the thresholds that have been set to meet the demand of the integrity requirements. If a fault can be detected, when six or more satellites are available, according to the relation between the test statistic value and the decision thresholds, a measurement fault can be isolated. The validation and analysis based on the real GPS data show that the method is feasible and practical to detect and isolate fault satellite.