| Abstract
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Montana 1:250,000 scale Land Use/Land Cover. Derived from USGS GIRAS files, some provided by the U.S. Bureau of Mines, others downloaded from the USGS World Wide Web server.The library tiles have the following source dates: Sandpoint 1981, Kalispell 1982, CutBank 1984, Shelby 1980, Havre 1982, Glasgow 1982, WolfPoint 1980, Spokane 1975, Wallace 1980, Choteau 1984, GreatFalls 1984, Lewistown 1985, Jordan 1982, Glendive 1974, Hamilton 1982, Butte 1984, WhiteSulphur 1972, Roundup 1982, Forsyth 1980, Ashton 1980, Miles City 1975, Elk City 1982, Dillon 1984, Bozeman 1972, Billings 1976, Hardin 1970, Ekalaka 1976, Dubois 1980, Cody, 1980.GIRAS is the U.S. Geological Survey's Geographic Information Retrieval and Analysis System. The U.S.G.S. digitized the data from 1:250,000 scale maps, which it created through field surveys and aerial photo interpretation. The minimum size of regions to be classified was 10 acres in urban areas, 40 acres in rural areas, linear manmade features at least 660 feet wide, and linear natural features at least 1320 feet wide.
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