specific surficial deposits and landscapes. Sensors can measure the directional flux of electromagnetic energy emanating from the earth's surface as a function of wavelength, viewing direction, and (or) polarization state (Baumgardner, Silva, Biehl, and Stoner, 1985, 1-4).
Two major advantages to using radar for imaging, as opposed to Landsat Thematic Mapper (TM) images, a more conventional source of remote-sensing data, are that radar can penetrate cloud cover, making every image useful, and that it can detect surface roughness in greater detail than Landsat. While Landsat reads reflected solar radiation from surface vegetation or landforms, imaging radar emits its own signal and reads the "backscatter," the returning signal that carries an image of the surface.
Direct linkages between remote sensing observations and soil properties involve the measurement of radiation emitted or scattered from the soil surface. Indirect linkages involve correlation of vegetation cover and landform with soil properties. Establishing such linkages, therefore, requires a basic understanding of (1) the interactions among soils, landscapes, and vegetation and (2) the scattering, absorption, and emission of electromagnetic energy from both vegetated and unvegetated surfaces.
Understanding of the long-term spatial and temporal trends of soil moisture fluctuations is also valuable in studies of desertification. It is generally unclear if soil moisture deficits are the cause or result of desertification, but they certainly accompany it. Long-term analysis of soil moisture in key desert fringe areas may increase understanding of the desertification process and improve the management of those sensitive areas. Soil reflectance represents a cumulative effect of a heterogeneous combination of mineral, organic, and fluid matter. The major factors influencing a soil's spectral reflectance signature include: mineralogy (mainly iron, Fe), organ...