| The Global Positioning System has demonstrated great potential to improve civilian aviation. However, before GPS can be used as a primary navigation system, the system's integrity and accuracy must be enhanced to meet the safety standards set by the Federal Aviation Administration.; To meet these requirements, the FAA proposed and initiated the development of the Wide Area Augmentation System for GPS. WAAS augments GPS with a ground network of GPS receivers to deliver the Wide Area Differential GPS corrections and system integrity alerts, as well as adding an extra ranging signal from a geo-synchronous satellite to increase the continuity and time availability of the service. This augmentation will enable WAAS to be the primary navigation system for en route flight, terminal area approach, and non-precision approach, and can provide accurate vertical guidance for Category I precision approach.; This thesis presents the real-time WAAS implementation to meet the accuracy requirement of Category I precision approaches, especially includes algorithms for calibrating interfrequency biases, and for creating an ionospheric grid model. A feedback algorithm for generating the confidence level of the ionospheric correction shown in this thesis is proven to be useful. Furthermore, an integrity monitoring indicator using {dollar}chisp2{dollar} has been proposed for detecting local ionospheric disturbances, which may represent the most significant threat to WAAS in the coming solar maximum around the year 2000. |
