REMOTE SENSING IN ARID REGIONS: THREE CASE STUDIES (SOUTHWESTERN KANSAS; MEATIQ DOME, EASTERN DESERT, EGYPT; AND KHARGA DEPRESSION, WESTERN DESERT, EGYPT).

摘要

Landsat multispectra; scanner (MSS) data have been combined with a variety of other datasets in three studies involving detection and monitoring of soil damage due to drought, mapping of rocks and sediments, and mapping of soil types and surface materials. Three distinct areas were studied: (1) Southwestern Kansas (near Garden City and Liberal); (2) Meatiq Dome (Eastern Desert, Egypt) and (3) Kharga Depression (Western Desert, Egypt).; From November 1975 through May 1976, severe wind erosion due to drought caused extensive damage to agricultural soils in Southwestern Kansas. Digital Landsat MSS data were used in conjunction with field mapping and Soil sampling to monitor changes to these soils over an eight-week period during the spring of 1976. Subtle changes in color and albedo, including progressive reddening of the area, were related to exposure of red subsoils and sands. Severity of wind erosion over this region appears to be controlled by land use.; Landsat data and sediment spectral reflectance measurements (from 0.4 to 1.1 micrometers) were combined with field mapping to map rock units in the Meatiq Dome, Egypt (26(DEGREES)N. Lat., 33(DEGREES)50'E. Long.). Two techniques were used to assist in mapping the Dome's complex igneous and metamorphic rocks: (1) Production of color composite images from Landsat data enhanced via principal components analysis, and (2) comparison of the Landsat data with principal components analysis, and (3) comparison of the Landsat data with sediment spectral reflectance measurements. Granitoid rocks within the Dome were distinguishable from the surrounding more mafic rocks, and boundaries established during field mapping were refined. The provenance and distribution of wadi sediments also were mapped in detail.; Surface materials in the Kharga Depression (25(DEGREES)10'N. Lat., 30(DEGREES)35'E. Long.) include vegetated oasis areas, sand-free soils, soils with thin, patchy sand cover, and sand-covered areas including barchan dune fields. Principal components enhancement of Landsat MSS data, followed by the use of simple clustering techniques, were used to map the surface materials in and near the Kharga Oasis. Four data clusters were delineated and used to thematically map surface units. Three of the clusters occur within oases, and the fourth cluster delineates sand-free soils and soils with patchy sand cover.