Improved urban navigation with direct positioning and specular matching

This paper introduces an assisted GPS direct positioning estimation (DPE) technique in conjunction with visibility and specularity matching techniques based on 3D building information for positioning in an urban environment. Results from static experiments in the city of Denver, CO are presented. The locations are chosen to demonstrate conditions where GPS signals reach the receiver in several different ways: a direct-line-of-sight (DLOS) path only; a combination of DLOS and non-line-of-sight (NLOS) paths known as multipath; and a strictly NLOS path with buildings blocking the DLOS path. Use of signal visibility and specular reflection predictions within the DPE can improve positioning. We show that when we explicitly account for visibility and have some indication of specularity the RMS position error is reduced from approximately 30 to 10 meters.