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

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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.