| This dissertation presents the implementation of a new method for determining a near-optimum siting geometry for critical Reference Stations in a Ground Based Augmentation System (GBAS) installation. The models developed in this research characterize the frequency content of the residual system errors, determine and quantify the presence of correlated residual error between two or more Reference Stations, and assess the impact to the user in terms of navigation system error (NSE). The method couples results from ranging error assessments with quantification of navigation system error, rather than relying on estimates of navigation system error based on probabilistic analysis of the system errors. System performance based on the proposed method of GBAS Reference Station siting has shown to provide mean navigation error of less than one centimeter over a 24-hour period. This unique contribution to the development of GBAS technology is a key element to ensure that a GBAS installation provides corrections to the users with integrity, accuracy, and continuity. Due to inherent errors in basic GPS, the GBAS provides these local ranging corrections to basic GPS measurements for in-view satellites. The algorithms for computing ranging corrections assume that the measurements taken at each of the four Reference Stations are statistically independent from each other. Local multipath can negatively impact this assumption, so careful attention to siting of the Reference Stations is required. The siting method presented in this dissertation provides a model that is superior to all existing siting models dependent on probabilistic measures of system performance. |
