Soil-water measurement using synthetic aperture radar in mountainous rangeland areas

Sudhir K. Goyal; Mark S. Seyfried; James A. DeShazer

doi:10.1117/12.262871

18 December 1996 Soil-water measurement using synthetic aperture radar in mountainous rangeland areas

Sudhir K. Goyal, Mark S. Seyfried, James A. DeShazer

Proceedings Volume 2907, Optics in Agriculture, Forestry, and Biological Processing II; (1996) https://doi.org/10.1117/12.262871
Event: Photonics East '96, 1996, Boston, MA, United States

Abstract

Airborne synthetic aperture radar (SAR)-derived soil moisture (m_v) estimates were evaluated using field measured and distributed hydrologic model simulated m_v values in the Reynolds Creek Experimental Watershed (RCEW), located in a semi-arid mountainous watershed in Southwest Idaho. A soil moisture inversion algorithm was developed by comparing L-HH SAR sigma⁰ (dB), corrected for surface roughness and topographic effects, with field measurements. The algorithm was found to be consistent with an algorithm developed in a previous study done on other rangelands. The corrected SAR-based soil moisture maps show relatively dry conditions at lower elevations and vice-versa, which is consistent with field observations. Change detection was found to give results similar to those from the corrected SAR, but it tends to give lower soil moisture values than the field measured or corrected SAR-based approaches. Out of the two SAR-based approaches used for the determination of m_v, change detection is simpler and adequate for the measurement of soil moisture changes. The corrected SAR approach is relatively difficult but it is better for the areas where absolute m_v measurements are required and SAR data under dry conditions are not available. The hydrologic model tended to overestimate surface m_v, which is what SAR senses. This was due to the failure of the model in accurately accounting for surface evaporation processes unless subsoil was relatively dry. In general, the overall trends in m_v, especially for 1989 and 1991, were reasonably represented but probably a little over the actual values. The soil moisture simulation model, corrected SAR, and ground measurements provided a unique mounds to study the moisture changes and distribution patterns in rangelands with an imaging SAR.

Citation Download Citation

Sudhir K. Goyal, Mark S. Seyfried, and James A. DeShazer "Soil-water measurement using synthetic aperture radar in mountainous rangeland areas", Proc. SPIE 2907, Optics in Agriculture, Forestry, and Biological Processing II, (18 December 1996); https://doi.org/10.1117/12.262871

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