These polygons are buffers around the points which represent the mine location. The buffers have an area of one acre. The points were plotted on 7.5' quadrangle maps which were the source for digiti- zing. The extent ofthe mines is unknown and the buffers were added to satisfy software restrictions. Areal accuracy cannot be estimated.
Positional accuracy is estimated based on the precision of the location.
The positional accuracies of the points are estimated to be 800 and 1600 meters, respectively. These are used to represent up to three levels of mining. Others may be 0 and blank. Tics are placed at the corners of each county. It resides in the Natural Resources Geographic Information System library.