GPS interferometric reflectometry: applications to surface soil moisture, snow depth, and vegetation water content in the western United States

GPS interferometric reflectometry is a new environmental sensing technique that can be used to measure near-surface soil moisture, snow depth, and vegetation water content variations. The spatial scale of this technique, ~1000 m, is intermediate to that of other in situ sensors (<1 m) and satellites (>100 km). Soil moisture and snow depth retrievals have accuracies of 0.04 m/m and 0.04 m, respectively. These accuracies are sufficient for many hydrologic applications. Fortuitously, GPS interferometric reflectometry can be used with consumergrade off the shelf GPS instruments that are operated by the geodetic, geophysical, and surveying communities. This means that GPS data from thousands of sites are potentially available for environmental scientists seeking new in situ data for soil moisture, snow depth, and vegetation water content. The technique can be applied to data from existing archives or for new sites. Although the accuracy of the technique has only been evaluated for the GPS constellation, the technique can also be used for other navigation constellations such as GLONASS, Galileo, and Beidou. © 2016 Wiley Periodicals, Inc.