This data is ordered by the WADNR numbering scheme,.i.e. by row and column. Each 7.5' quad has a unique ID number. The first two digits of the ID number count down from 49 degress. The last two digits count east from 125 degrees.

The information that follows the quad number is extracted from the file header. Some of the names are not the official quad names. The header may contain information about the origianl photos, the software, and the contour interval.

Most of these Digital Elevation Models are derived from the digitized contour lines (at 40' or smaller intervals) on the 7.5' (1:24000) quad sheets. Some were derived from aerial photographs at a coarser sampling interval. You should consider whether you would prefer to use the 10-meter DEMs instead. Although to 10-meter DEMs are derived from the same contours, they are made with better algorithms. 10-meter DEMs resampled to 30 meters will range from slightly better to worlds better than these 30-meter DEMs.

The USGS posts a seamless dataset at http://edcnts14.cr.usgs.gov/Website/store/viewer.htm