Authors: Jeffrey Colby*, Appalachian State University, Michael Bishop, Texas A&M University, Brennan Young, Texas A&M University, Roberto Furfaro, University of Arizona, Enrico Schiassi, University of Arizona, Zhaohui Chi, Texas A&M
Topics: Remote Sensing, Mountain Environments, Physical Geography
Keywords: mountain environments, multispectral imagery, Nanga Parbat Himalaya, topographic correction, radiation-transfer cascade, radiometric calibration, topographic complexity
Session Type: Poster
Presentation File: No File Uploaded
Research involving anisotropic reflectance correction (ARC) of multispectral imagery to account for topographic effects has been ongoing for approximately 40 years. A large body of research has focused on evaluating empirical ARC methods, resulting in contradictory results. Consequently, our research objective was to evaluate commonly used ARC methods using first-order radiation-transfer modeling to simulate ASTER multispectral imagery over Nanga Parbat, Himalaya. We accounted for atmospheric absorption and scattering, direct and diffuse-skylight irradiance, land cover structure, and surface biophysical variations to evaluate ARC methods in reducing multi-scale topographic effects. Our results clearly revealed that the empirical methods we evaluated could not reasonably account for multi-scale topographic effects. The CCOR and SCS+C methods were able to remove topographic effects, given the Lambertian assumption, although atmospheric correction was required, and we did not account for other primary and secondary topographic effects that are thought to significantly influence spectral variation in imagery acquired over complex mountains. Collectively, our simulation and evaluation procedures strongly suggest that empirical ARC methods cannot be used to address the problem of multi-scale topographic effects in imagery. Results indicate that atmospheric correction is essential, and most methods failed to adequately produce the appropriate magnitude and spatial variation of surface reflectance in corrected imagery. Results were also wavelength dependent, as topographic effects influence radiation-transfer components differently in different regions of the electromagnetic spectrum.
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