Acquisition - Processing Steps
Manual interpretation of aerial photographs acquired from NASA high-altitude missions and other sources were first used to compile the land use land cover maps. Secondary sources from earlier land use maps and field surveys were also incorporated into the LULC maps as needed. At a later time, the LULC maps were digitized to create a national digital LULC database. The evolution of this process resulted in the creation of the Geographic Information Retrieval Analysis System (GIRAS).
Initial source preparation involves the transfer of field survey information, photo classification detail and associated line work to a base map for digitization. This may be done through stereo compilation or monoscopic transfer techniques. Adjacent maps are also checked to ensure continuity. The maps are digitized and the appropriate classification codes are assigned for processing through GIRAS and checked for accuracy. All LULC data conform to the Universal Transverse Mercator (UTM) projection.
Extent of Coverage
Applications and Related Data Sets