Earth resources: A continuing bibliography with indexes, issue 21

A bibliography list of 369 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1979 and March 31, 1979 is presented. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economic analysis.