Measurement-Based Multipath Corrections for GPS Sites

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0003943LarsonDespite the development of an impressive GPS infrastructure for precise orbit determination and many advances in GPS modeling and analysis techniques, significant error sources remain. As continuously operating GPS arrays continue to be deployed throughout the world to study geophysical processes with signals below 1 mm/yr, the need to eliminate all systematic errors is critical. Multipath represents one of the largest errors in GPS applications today. There is currently no standard technique to remove multipath errors in high precision GPS software used by the geophysics community. Failure to correct for the multipath environment at a GPS site produces a time-varying systematic error in GPS estimates which degrades the accuracy of the system.Support form this grant will be used to develop an approach for correcting GPS multipath errors that borrows on technologies developed by aerospace engineers for spacecraft attitude determination. The technique uses the signal-to-noise ratio (SNR) to estimate corrections to the GPS phase observables. Although routinely collected by GPS receivers, SNR data are not currently used in high precision GPS software. This SNR based multipath correction technique can be used both on older datasets as well as new GPS data. And because the technique uses SNR data collected simultaneously with the phase data, it is sensitive to time varying changes at GPS sites. ***