Sec. 22.159  Computation of average terrain elevation.

    Average terrain elevation must be calculated by computer using 
elevations from a 30 second point or better topographic data file. The 
file must be identified. If a 30 second point data file is used, the 
elevation data must be processed for intermediate points using 
interpolation techniques; otherwise, the nearest point may be used. In 
cases of dispute, average terrain elevation determinations can also be 
done manually, if the results differ significantly from the computer 
derived averages.
    (a) Radial average terrain elevation is calculated as the average of 
the elevation along a straight line path from 3 to 16 kilometers (2 and 
10 miles) extending radially from the antenna site. If a portion of the 
radial path extends over foreign territory or water, such portion must 
not be included in the computation of average elevation unless the 
radial path again passes over United States land between 16 and 134 
kilometers (10 and 83 miles) away from the station. At least 50 evenly 
spaced data points for each radial should be used in the computation.
    (b) Average terrain elevation is the average of the eight radial 
average terrain elevations (for the eight cardinal radials).
    (c) For locations in Dade and Broward Counties, Florida, the method 
prescribed above may be used or average terrain elevation may be assumed 
to be 3 meters (10 feet).