New Approaches to Retrieving Soil

Moisture from SAR data

Keith Morrison

University of Reading

Soil Moisture Workshop

25 January 2017

Soil Moisture from SAR

• Radar remote sensing uses backscatter

• Backscatter has a dual dependence upon surface-roughness and moisture

moisture, mv

texture (sand, clay)

Moisture Phase Sensitivity

C-band Radarsat

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Laboratory Investigation

Laboratory Investigation

Moisture – Phase Behaviour

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Morrison,K., Bennett,J.C. and Nolan,M. Using DInSAR to Separate Surface and Subsurface Features.IEEE Transactions on Geoscience and Remote Sensing, 51, 6, pp.3424-3430. 2013.

Morrison,K. Mapping Subsurface Archaeology with SAR. Archaeological Prospection, 20, 2, pp.149–160. 2013

The phase reflecting from a sub-surface feature is:

1) linear2) independent of incidence angle

Interferometric Model

F. de Zan, A. Parizzi, and P. Prats. A proposal for a SAR interferometric model of soil moisture IGARSS Proceedings, pages 630–633, 2012.

Model vs. Field

ESAR AgriSAR 2006

F. de Zan, A. Parizzi, and P. Prats. A proposal for a SAR interferometric model of soil moisture IGARSS Proceedings, pages 630–633, 2012.

Virtual Bandwidth SAR

(VB-SAR)

6.4GHz

VB-SAR – First Demonstration

Drying sandy loamC-Band, imaging geometry i=20°

Δmv=0.098 to 0.027

Real Bandwidth 0.15GHzVirtual bandwidth 3.38GHz

SAR Image

VB-SAR Image

Summary

Interferometry of soil shows:

• definite moisture-phase relationship

Understand phase change as:• return from within soil• surface return little changed• due to changing dielectric = proxy for moisture

Opportunities• added-value of backscatter-derived moistures• new insights• moisture profiles• sub-surface imaging

Exciting “discovery” phase:

• Groups to watch - University of Reading, ETH-Zürich, DLR.