Journal ArticleDOI
Measuring soil moisture with imaging radars
P. Dubois,J.J. van Zyl,T. Engman +2 more
TLDR
An empirical algorithm for the retrieval of soil moisture content and surface root mean square (RMS) height from remotely sensed radar data was developed using scatterometer data and inversion results indicate that significant amounts of vegetation cause the algorithm to underestimate soil moisture and overestimate RMS height.Abstract:
An empirical algorithm for the retrieval of soil moisture content and surface root mean square (RMS) height from remotely sensed radar data was developed using scatterometer data. The algorithm is optimized for bare surfaces and requires two copolarized channels at a frequency between 1.5 and 11 GHz. It gives best results for kh/spl les/2.5, /spl mu//sub /spl upsi///spl les/35%, and /spl theta//spl ges/30/spl deg/. Omitting the usually weaker hv-polarized returns makes the algorithm less sensitive to system cross-talk and system noise, simplifies the calibration process and adds robustness to the algorithm in the presence of vegetation. However, inversion results indicate that significant amounts of vegetation (NDVI>0.4) cause the algorithm to underestimate soil moisture and overestimate RMS height. A simple criteria based on the /spl sigma//sub hv//sup 0///spl sigma//sub vv//sup 0/ ratio is developed to select the areas where the inversion is not impaired by the vegetation. The inversion accuracy is assessed on the original scatterometer data sets but also on several SAR data sets by comparing the derived soil moisture values with in-situ measurements collected over a variety of scenes between 1991 and 1994. Both spaceborne (SIR-C) and airborne (AIRSAR) data are used in the test. Over this large sample of conditions, the RMS error in the soil moisture estimate is found to be less than 4.2% soil moisture. >read more
Citations
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Journal ArticleDOI
The Soil Moisture Active Passive (SMAP) Mission
Dara Entekhabi,Eni G. Njoku,Peggy O'Neill,Kent Kellogg,Wade T. Crow,W. Edelstein,Jared Entin,Shawn D Goodman,Thomas J. Jackson,Joel T. Johnson,John S. Kimball,Jeffrey R. Piepmeier,Randal D. Koster,Neil R.W. Martin,Kyle C. McDonald,Mahta Moghaddam,Susan Moran,Rolf H. Reichle,Jiancheng Shi,Michael W. Spencer,Samuel W Thurman,Leung Tsang,Jakob van Zyl +22 more
TL;DR: The Soil Moisture Active Passive mission is one of the first Earth observation satellites being developed by NASA in response to the National Research Council's Decadal Survey to make global measurements of the soil moisture present at the Earth's land surface.
Journal ArticleDOI
Inversion of surface parameters from polarimetric SAR
TL;DR: It demonstrates how three polarimetric parameters, namely the scattering entropy, the scattering anisotropy, and the alpha angle may be used in order to decouple surface roughness from moisture content estimation offering the possibility of a straightforward inversion of these two surface parameters.
Journal ArticleDOI
Estimation of bare surface soil moisture and surface roughness parameter using L-band SAR image data
TL;DR: Application of the inversion algorithm to the co-polarized measurements of both AIRSAR and SIR-C resulted in estimated values of soil moisture and roughness parameter for bare and short-vegetated fields that compared favorably with those sampled on the ground.
Journal ArticleDOI
Operational readiness of microwave remote sensing of soil moisture for hydrologic applications
Wolfgang Wagner,Günter Blöschl,Paolo Pampaloni,Jean-Christophe Calvet,Bizzarro Bizzarri,Jean-Pierre Wigneron,Yann Kerr +6 more
TL;DR: In this article, the authors reviewed recent progress made with retrieving surface soil moisture from three types of microwave sensors -radiometers, Synthetic Aperture Radars (SARs), and scatterometers.
Journal ArticleDOI
The use of Imaging radars for ecological applications : A review
TL;DR: In this article, a panel of 16 scientists met to review the utility of SAR data for monitoring ecosystem processes and found that the demonstrated capabilities of imaging radars for investigating terrestrial ecosystems could best be organized into four broad categories: classification and detection of change in land cover; estimation of woody plant biomass; monitoring the extent and timing of inundation; and monitoring other temporally-dynamic processes.
References
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TL;DR: In this article, the relationship between various linear combinations of red and photographic infrared radiances and vegetation parameters is investigated, showing that red-IR combinations to be more significant than green-red combinations.
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Journal ArticleDOI
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