Effects of the soil surface roughness and soil moisture content on the soil spectral signature
The purpose of the current study is to simulate conditions and phenomena such as specular reflections and soil roughness that are encountered when airborne or satellite hyperspectral images are acquired. Relationships between soil moisture and soil surface roughness as well as their effect on the soil spectral signature are investigated. Seven natural (not sieved, not dried, undisturbed) samples of soils were used for the experiments. They have heterogeneous characteristics and their volumetric moisture content (VMC), as well as their surface roughness were artificially changed. The spectral measurements took place under laboratory conditions with a full spectrum (350nm-2500nm) ASD spectroradiometer. Spectral similarity measurements and spectral matching were applied on the soil spectral signatures in order to investigate sensibility of soil spectral signatures in various roughness and VMC values. To study the effect of soil moisture and surface roughness at the soil spectral signature, a new metric, the relative difference (RD) metric is defined and used. The variation of soil signature intensity in terms of surface roughness at different soil moisture levels is also investigated. Moreover, the Normalized Difference Soil Moisture Index (NSMI) was used for estimating the VMC. It was proved robust, yielding accurate results for soils that do not present staggering water on their surface.
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