GPS Solutions

, Volume 12, Issue 3, pp 173–177

Using GPS multipath to measure soil moisture fluctuations: initial results

  • Kristine M. Larson
  • Eric E. Small
  • Ethan Gutmann
  • Andria Bilich
  • Penina Axelrad
  • John Braun
Original Article

DOI: 10.1007/s10291-007-0076-6

Cite this article as:
Larson, K.M., Small, E.E., Gutmann, E. et al. GPS Solut (2008) 12: 173. doi:10.1007/s10291-007-0076-6

Abstract

Measurements of soil moisture are important for studies of climate and weather forecasting, flood prediction, and aquifer recharge studies. Although soil moisture measurement networks exist, most are sparsely distributed and lack standardized instrumentation. Measurements of soil moisture from satellites have extremely large spatial footprints (40–60 km). A methodology is described here that uses existing networks of continuously-operating GPS receivers to measure soil moisture fluctuations. In this technique, incoming signals are reflected off and attenuated by the ground before reception by the GPS receiver. These multipath reflections directly affect signal-to-noise ratio (SNR) data routinely collected by GPS receivers, creating amplitude variations that are a function of ground reflectivity and therefore soil moisture content. After describing this technique, multipath reflection amplitudes at a GPS site in Tashkent, Uzbekistan are compared to estimates of soil moisture from the Noah land surface model. Although the GPS multipath amplitudes and the land surface model are uncalibrated, over the 70-day period studied, they both rise sharply following each rainfall event and slowly decrease over a period of ∼10 days.

Keywords

GPS Multipath SNR Soil moisture 

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Kristine M. Larson
    • 1
  • Eric E. Small
    • 2
  • Ethan Gutmann
    • 2
  • Andria Bilich
    • 1
  • Penina Axelrad
    • 1
  • John Braun
    • 3
  1. 1.Department of Aerospace Engineering SciencesUniversity of ColoradoBoulderUSA
  2. 2.Department of Geological SciencesUniversity of ColoradoBoulderUSA
  3. 3.UCARBoulderUSA