9708251 Davis The Global Positioning System (GPS) is used by earth scientists for accurately recording strain in the Earth's crust in a wide range of applications that include the study of plate motions, intraplate deformation, pre-, syn- and post-seismic fault motions, pre-eruption volcanic activity, glacier flow, and sea level monitoring. In such applications, the positioning precision required is very demanding, usually on the order of a centimeter or less in the horizontal and vertical dimensions. The GPS receiver and antenna system is one of significant sources of error which, if better understood and corrected, could lead to significant improvement. This award provides funding for a team of experts at the Smithsonian Astrophysical Observatory, MIT, and the University NAVSTAR Consortium to develop algorithms to extract multipath effects from observed GPS signal-to-noise ratios, numerically model GPS antenna characteristics, and develop an on-site Multipath Calibration System for the purpose of reducing GPS errors below the centimeter level. ***
