DOQQs are Digital Orthophoto Quarter Quads - each Quad is split into 
NW, NE, SE, and SW quadrats.  Therefore, to obtain an entire quad
requires that you download 4 files.  The quarter quad is indicated in
the download file name.

The DOQQs are being made available in Idaho Transverse Mercator (IDTM)
projection, and have been compressed into MrSID format.  To view these
images in ArcView, it is necessary to add the MrSID extension to your
project.  This is a standard ArcView extension and is installed with
the program.  To view these images in ArcInfo requires version 8.

If you have any questions or problems with any of these files, contact
Kindra Serr at (208) 282-3606.