About the USGS data formats: You can get "Data Users Guides" from the USGS on their various data formats, such as the 1:2000000,1:100000, or 1:24000 dlgs, DEMs, Land Use and Land Cover Digital Data... Call 1-800-maps or 1-703-860-6045 or write to Earth Sciences Information Center USGeological Survey 507 National Center Reston, VA 22092 -N.