AUGMENTING GPS BY GROUND-BASED PSEUDOLITE SIGNALS FOR AIRBORNE SURVEYING APPLICATIONS

Abstract

This paper discusses some issues associated with the implementation of ground-based pseudolite augmentation for GPS airborne surveying applications. For instance, not only should two antenna offsets (one on the top of, and the other underneath, the platform) be corrected for, but the number, the location, and the geometric distribution of the pseudolites on the ground has to be carefully considered. Initial analyses have shown that the accuracy requirement for the attitude parameters is dependent on the magnitude of the offsets between the two antennas. In addition, a series of simulations has demonstrated that pseudolite augmentation can significantly improve the quality of the positioning solutions, especially the vertical component accuracy (due to the negative elevation of the pseudolites). The optimal number and locations of the pseudolites are dependent on the satellite geometry. Based on selected optimization criteria, a comprehensive search would typically be needed for a specific application. A geometric analysis and measurement testing procedure for this purpose will be described in this paper.