金曜日セミナー:(2019年9月20日) Dr. Kristine Larson (University of Colorado Boulder)

GPS Can’t Do That, Can It?
How making GPS into a better seismometer led to the development of new snow, soil moisture, vegetation, and water level sensors

Kristine M. Larson
Professor Emerita of Aerospace Engineering Sciences
University of Colorado

About fifteen years ago I began working on developing techniques so that GPS could be used to measure ground displacements during large earthquakes. At the time, almost all geodesists estimated station positions once per day, as this is entirely adequate for tectonic applications.  Standard geodetic analysis tools (then and now) ignore the error caused by signals that reflect off the land surface. My group quickly realized that surface reflections were the largest error source in GPS seismology and developed tools to mitigate their impact. That early work in GPS seismology ultimately led us to new work in GPS interferometric reflectometry - where reflected GPS signals are used to turn a GPS antenna into a bi-static radar. The reflected GPS signals can be used to measure soil moisture, snow accumulation, tides and storm surges, permafrost melt, and vegetation water content.  In this talk I will first provide some background on GPS for tectonic and seismic applications, explain how GPS interferometric reflectometry works, and then share environmental products derived from GPS data.