Sec.  80.757   Topographical data.

   (a) In the preparation of profile graphs and in determining the location and
   height  above sea level of the antenna site, the elevations or contour
   intervals must be taken from U.S. Geological Survey topographic quadrangle
   maps, U.S. Army Corps of Engineers maps or Tennessee Valley Authority maps,
   whichever is the latest, for all areas for which maps are available. If such
   maps are not published for the area in question, the next best topographic
   information must be used. The maps used must include the principal area to
   be  served.  U.S. Geological Survey topographic quadrangle maps may be
   obtained from the Eastern Distribution Branch, U.S. Geological Survey, 1200
   South  Eads Street, Arlington, VA 22202, for maps of areas east of the
   Mississippi River, including Minnesota, Puerto Rico, and the Virgin Islands,
   and from the Western Distribution Branch, U.S. Geological Survey, Federal
   Center, Denver CO 80225, for maps of areas west of the Mississippi River,
   including Alaska, Hawaii, Louisiana, Guam and American Samoa. Sectional
   aeronautical charts are available from the Distribution Division, National
   Ocean Service, Riverdale, MD 20840.

   (b)  In  lieu  of  maps, the average terrain elevation may be computer
   generated, using elevations from a 30 second point or better topographic
   data file such as those available for the U.S. Geological Survey's National
   Geographic  Information Center or the National Oceanic and Atmospheric
   Administration's National Geophysical Data Center. In case of dispute maps
   will be used to determine the correct value.