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Kristine Larson and her colleagues at the University of Colorado at Boulder used GPS signal reflections (which are a source of unwanted noise in geodetic applications) to measure near-surface soil moisture and its change with time. Soil moisture observations are critical for weather and climate forecasts, both to improve agricultural yields and to mitigate the impact of drought and extreme weather events. A GPS-based soil moisture network would complement planned satellite soil moisture missions, providing thousands of calibration points across the globe.
Other related links:
http://www.springerlink.com/content/m76550834v2n4242/
http://arstechnica.com/science/news/2009/01/exploiting-the-noise-in-gps-data.ars
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Figure 1 - At a PBO station in Marshall, Colorado, the reflected GPS signals (colored dots in figure, above) show a strong correlation with in situ soil moisture measurements (gray band); both display soil drying after discrete rainfall events (blue bars). Larson, K.M., Small, E.E., Gutmann, E., Bilich, A., Axelrad, P., and Braun, J., 2008a, Using GPS multipath to measure soil moisture fluctuations: initial results: GPS Solutions, v. 12, no. 3, p. 173-177. Larson, K.M., Small, E.E., Gutmann, E.D., Bilich, A.L., Braun, J.J., and Zavorotny, V.U., 2008b, Use of GPS receivers as a soil moisture network for water cycle studies: Geophysical Research Letters, v. 35, p. 24.
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