Distribution Information 7. Quadrangle names and standard identifiers are included with the data set. The current version corrects problems identified in the February 1992 version. Attribute restructuring in March 1996. The 100K and 250K index layers are derived from this parent layer.
All polygons are closed and lines intersect where intended.
The source attributes were tied to the lower left corner of each quad. By generating a point coverage from these coordinates and shifting the point positions to the northwest, label points for this coverage were effectively created. The coverage was then projected into UTM Zone 15. OLD USGS standard, New USGS standard.