ABSTRACT

This chapter discusses the physics of electromagnetic radiation and later the spectral signature characteristic of objects and materials. Objects reflect electromagnetic radiation emitted by other objects and emit radiation of their own. In theory, spectral signatures permit the identification of materials and features on the earth’s surface, such as crops, forests, or minerals, however, there are complicating factors. Spectral pattern recognition is usually based upon independently processing each image pixel data. The chapter describes several fundamental laws related to radiation that are necessary in the context of remote sensing. The notion of a blackbody is theoretical because in nature all objects reflect at least a small portion of the radiation that strikes them. Remote sensing apparatus are designed to take advantage of the atmospheric windows in order to form images; it makes little practical sense to build a device sensitive to a portion of the electromagnetic spectrum that is filtered out by atmospheric gases.