Modeling the spectral reflectance of wet soils
Abstract
The technical objective of the proposed effort is to develop a physics-based model that functionally describes the effect of wetting on soil reflectance. The proposed effort seeks to achieve the stated technical objective by developing adaptations to the description of the interaction of light with wetted particles that could be incorporated into a physical model. The proposed effort will begin with a series of controlled experiments using well-characterized soils and proxy materials (e.g., well-sorted silica particles and glass spheres). The soil characteristics (bulk density, porosity, moisture content, etc.) will be adjusted for each sample in order to observe the resulting change in reflectance. Several size ranges of each material will be used (e.g., 50, 100 and 200 microns). The selection will enable adjustment of the pore sizes and the ability to distinguish experimentally among the several mechanisms controlling reflectance (Fresnel reflectance, multiple internal reflections, absorption by water and by particles, etc.). The density (and thus the pore space) of the samples will be adjusted both by conducting experiments using a range of different particle sizes, and by adjusting the density for a particular particle size using air pluviation. These experiments will provide the basis for the development and initial testing of a radiative transfer model. The Hapke model will be used as a starting point since it is the physics-based model that is most widely used and cited. Modifications, however, will be required; and simpler, phenomenological models, optimized to the experimental results, will also be considered. The proposed research effort will be directed toward refining and reconfiguring the models to better represent the observed data. Furthermore, experiments will be expanded to examine more realistic soils with the goals of understanding the underlying optics of reflectance from granular materials and, as far as possible, adapting the model to account for more realistic conditions (e.g., complex mixtures, surface roughness, crusting, local inhomogeneity, etc.).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 12, 2017
- Source ID
- W911NF1510071
Entities
People
- William Philpot
Organizations
- Army Contracting Command
- Cornell University
- United States Army