Abstract
Although characteristics of visible and near-infrared spectra (0.4 - 2.5 micrometer) of rocks are dominated by electronic processes and molecular vibration processes that is related to chemical composition and structure of rocks, external behavior of spectra of rocks is adjusted by some factors, such as environmental conditions, physical structure of surface and viewing geometry, etc. The spectra of rocks can vary with the changes of these factors to a certain extent. It is obvious that variability of spectra of ground objects would degrade the interpretability of remote sensing images, and especially degrade the effectiveness of techniques of discriminating rocks based on remote sensing spectral features and spectral indexes to a large extent. To discriminate earth surface mineralogy and lithology more effectively and efficiently by remote sensing, especially by hyperspectral remote sensing, requires a good knowledge of variability of spectra of rocks. This paper describes and analyzes variability of reflectance spectra of rocks sampled in Zhangjiakou district of Hebei Province of China, under different light incident direction and incident angle, viewing direction and viewing angle, surface forms of rocks, grades of samples, and types and extents of weathering, etc.
