Gps-based Precision Approach and Landing Navigation Emphasis on Inertial and Pseudolite Augmentation and Differential Ionosphere Effect

The Di erential Global Positioning System-based precision approach and landing architectures proposed by the Federal Aviation Administration (FAA) include the Wide Area Augmentation System (WAAS) and the Local Area Augmentation System (LAAS) for performing landings in Category (CAT) I and CAT III minima, respectively. The Required Navigation Performance (RNP) for GPS-based satellite navigation systems includes accuracy, continuity, integrity and availability. Previous studies have demonstrated that both the WAAS and the LAAS can provide the required accuracy. Current research focuses on the issues of integrity, continuity and availability. Speci cally, pertinent research indicates that both systems are susceptible to possible interference and jamming that could damage their continuity and availability. Additionally, the carrier smoothed code algorithm is the current choice by the FAA for LAAS. The algorithm's in uence on the error due to the di erential ionosphere remains unexamined. Therefore, this thesis discusses the following topics: Inertial backup of GPS-Based precision approach and landing systems. This topic includes { Accuracy and continuity evaluation of an integrated WAAS/INS system. { Accuracy comparison among various LAAS algorithms and the integrated LAAS/INS system. { A backup system based on the integration of three pseudolites (PLs) with INS. The impact of the di erential ionosphere error on the LAAS. This topic includes iv { Evaluation of the threat. { Seeking solutions and evaluating their costs and bene ts. Experimental data are used to develop the error models for both the WAAS and LAAS and the linear covariance analysis technique is used for the performance analysis. Analysis results indicate the following: Integrating an INS with WAAS can provide a temporary backup for GPS outages. This temporary backup is accomplished by using the INS which has been calibrated by the WAAS position update to satisfy the CAT I requirement. GPS outages clearly demonstrate the integration bene t of the WAAS/INS. However, the possibility of extending the integrated system performance to satisfy the CAT II requirement is limited. The performance of the integrated LAAS/INS system is comparable to that of the LAAS using a carrier phase algorithm. The 3-PLs/INS system can provide touch down performance in the absence of the data link, pseudolite synchronization and GPS signals. The di erential carrier smoothed ionosphere delay (DCSID) ensures that the ionosphere spatial decorrelation error is not negligible. This research has identi ed the DCSID as a threat to LAAS availability and an in uence on the time constant of the carrier smoothed code. The DCSID e ect can be controlled via the ionosphere monitoring and calibration algorithm developed herein. However, this will require an increase in the bandwidth of the data link that transmits the ground monitored ionosphere gradients.