Effect of Terrain Masking on GPS Position Dilution of Precision

Published values for position dilution of precision (PDOP) that will be achieved with the GPS 21 primary satellite constellation have assumed an unobstructed view of the sky. Masking of the receiver field of view due to terrain will be an important consideration for many applications. This paper presents an analysis of PDOP for a GPS receiver in an idealized valley. It is shown that PDOP varies significantly with time of day, can be large for a substantial fraction of a 1 day period, and is a strong function of latitude. The results characterize GPS receiver performance relevant to land vehicles, aircraft at low altitudes, and some precision guided missiles.