| This thesis is concerned with a theoretical development of Receiver Autonomous Integrity Monitoring (RAIM) algorithms. Integrity characterizes a navigation system ability to provide timely warning to users when the Global Positioning System (GPS) should not be used for navigation. RAIM algorithms detect, identify GPS anomalies and satellite failures and provide the Horizontal Protection Level (HPL). HPL means the smallest detectable horizontal position error with given probabilities of a false alert and missed detection. The developed algorithms use carrier phase measurements, which compared with code measurements can provide precise positioning and an extremely high level of GPS integrity due to setting a very tight fault detection threshold and HPL. First the linear model based on accumulating a few epochs of single difference carrier phase measurements is presented. Then the estimated integer ambiguities available from the positioning solution are used to develop the other single difference linear model. The typical fault detection and identification methods, used for code measurements, are applied to these linear models, leading to various single difference algorithms. The double difference method is also derived. The maximum position separation technique is used to derive the position space based method, implemented through a set of Kalman filters. Finally, computer simulations are performed to compare the developed various algorithms. |
