Estimates are that features have an average locational error of at least plus/minus 100 feet.įor more information on this and other datasets, please visit the Illinois Geospatial Data Clearinghouse. Errors in the location of a given feature are dependent on the accuracy of the original maps and on the accuracy of digitizing. The data were digitized in the late 1960s and in 1984-85 from 7.5- and 15-minute USGS topographic quadrangles. The data were originally developed, however, in a custom Lambert Conformal Conic projection and were distributed in that coordinate system for several years. 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.
Polygon attributes identify meridian, township, range. Line attributes identify state, township and range boundaries, principal meridians, and base lines. View In: ArcGIS JavaScript ArcGIS Online map viewer Google Earth ArcMap ArcGIS Explorer View Footprint In: ArcGIS Online map viewer Service Description: This dataset contains townships from the Illinois Public Land Survey System in line and polygon form.
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