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This data set contains Indian Treaty boundary lines from the Illinois Public Land Survey System.
The nominal scale is 1:62,500. As of 2003, the data are typically distributed in geographic coordinates (longitude and latitude), decimal degrees, and the North American Datum (NAD) of 1983, and this is the default spatial reference of the ArcSDE feature dataset in which the data are stored. The data were originally developed, however, in a custom Lambert Conformal Conic projection and were distributed in that coordinate system for several years.
The data were digitized in the late 1960s and in 1984-85 from 7.5- and 15-minute USGS topographic quadrangles. Errors in the location of a given feature are dependent on the accuracy of the original maps and on the accuracy of digitizing. Estimates are that features have an average locational error of at least plus/minus 100 feet.
For more information on this and other datasets, please visit the <a href="http://clearinghouse.isgs.illinois.edu/data/plss/indian-treaty-boundary-lines">Illinois Geospatial Data Clearinghouse</a>. |