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The U.S. Geological Survey is currently producing land use and land cover maps and associated overlays (e.g., political units) for the United States. These maps are being digitized, edited, and incorporated into a digital data base. The data will be available to the public in both graphic and digital form, and statistics derived from the data will be published. To accomplish these tasks the Geographic Information Retrieval and Analysis System (GIRAS) has been designed and developed. GIRAS is designed to accept digitizer input, provide comprehensive editing facilities, produce cartographic and statistical output, permit retrieval and analysis of data, and exercise data base management tasks. The editing and output procedures are currently operational and utilize an arc segment, polygon approach in a production mode. The system incorporates facilities for gridding the polygon data to make it compatible with grid-based data sources. Current system development is focused upon an interactive data base to enable immediate retrieval and display of map information. Users will be able to search for either locations or attributes and display results in a graphic or tabular form.
Mitchell et al. (Sat,) studied this question.