Objects having different surface features reflect or absorb the electromagnetics radiation in
different ways. The reflectance properties of an object depend on the particular material
and its physical and chemical state (e.g. moisture) the surface roughness as well as the
geometric circumstances (e.g. incidence angle of the sunlight). The most important surface
features are color, structure and surface texture.
These differences make it possible to identify different earth surface features or materials by
analyzing their spectral reflectance patterns or spectral signatures. These signatures
can be visualized in so called spectral reflectance curves as a function of wavelengths.
This chapter reviews the remote sensing of 3 basic types of Earth features: 1) clear
water, 2) green vegetation, and 3) dry bare soil.