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 
typographical 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,

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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]