Multipath Correction for Global Positioning System Satellite Range Measurements

Two methods are proposed to reduce GPS range and carrier phase multipath. Both methods are based on the assumption that multipath can be described as a function of elevation and azimuth. The proposed methods determined site-specific "multipath correction maps". The first method forms linear combinations of the four GPS observation types to compute range multipath as a function of elevation and azimuth. The advantage of this method is its simplicity and its potential for automatically updating the "multipath correction maps". However, the method is based on approximations that must be verified as part of the proposed research. For the second method we will design a "zero-multipath" antenna setup. This "zero-multipath" antenna, operated on a high, portable tower shall be used in differential mode to monitor multipath at a selected site. This second technique can determine site-specific corrections in real-time or post-processing GPS processing packages. During Phase I we will develop hardware, software, and experimentally test the feasibility of both multipath reduction approaches.