Sec.  73.312   Topographic data.

   (a) In the preparation of the profile graphs previously described, and in
   determining the location and height above mean sea level of the antenna
   site, the elevation or contour intervals shall be taken from United States
   Geological Survey Topographic Quadrangle Maps, United States Army Corps of
   Engineers Maps or Tennessee Valley Authority maps, whichever is the latest,
   for  all areas for which such maps are available. If such maps are not
   published for the area in question, the next best topographic information
   should be used. Topographic data may sometimes be obtained from state and
   municipal  agencies.  The  data from the Sectional Aeronautical Charts
   (including bench marks) or railroad depot elevations and highway elevations
   from road maps may be used where no better information is available. In
   cases where limited topographic data can be obtained, use may be made of an
   altimeter in a car driven along roads extending generally radially from the
   transmitter site.

   (b)  The  Commission  will  not  ordinarily  require the submission of
   topographical maps for areas beyond 24 km (15 miles) from the antenna site,
   but the maps must include the principal city or cities to be served. If it
   appears necessary, additional data may be requested.

   (c) The U.S. Geological Survey Topography Quadrangle Sheets may be obtained
   from the U.S. Geological Survey Department of the Interior, Washington, DC
   20240. The Sectional Aeronautical Charts are available from the U.S. Coast
   and Geodetic Survey, Department of Commerce, Washington, DC 20235. These
   maps may also be secured from branch offices and from authorized agents or
   dealers in most principal cities.

   (d) In lieu of maps, the average terrain elevation may be computer generated
   except in cases of dispute, using elevations from a 30 second, point or
   better topographic data file. The file must be identified and the data
   processed  for  intermediate  points  along  each  radial using linear
   interpolation techniques. The height above mean sea level of the antenna
   site must be obtained manually using appropriate topographic maps.

   [ 28 FR 13623 , Dec. 14, 1963, as amended at  31 FR 10126 , July 27, 1966;  49 FR 48937 , Dec. 17, 1984;  58 FR 44950 , Aug. 25, 1993;  63 FR 33877 , June 22,
   1998]