A Real-Time Wide Area Differential GPS System

Abstract

This paper describes the system architecture, algorithms, and results from an operating Wide Area Differential GPS (WADGPS) system spanning the continental United States (CONUS). With single-frequency GPS user equipment and improved positioning algorithms, real-time root mean square (RMS) user position accuracy is typically better than 25 cm in the horizontal components and 50 cm in the vertical with current levels of ionospheric activity. Dual-frequency users have a slightly degraded accuracy of 35 cm horizontal and 75 cm vertical. There may be some degradation in single-frequency positioning during solar maximum or ionospheric storms. We expect that improvements in smoothing and editing techniques for the dual-frequency user will yield better positions than those yielded for single-frequency users during peak solar activity. In addition to commercial applications, the software for estimation of the WADGPS corrections is being adapted for use in the Federal Aviation Administration's (FAA) Wide Area Augmentation System (WAAS) and will be installed in the FAA's National Satellite Test Bed (NSTB).