Sec. 24.53  Calculation of height above average terrain (HAAT).

    (a) HAAT is determined by subtracting average terrain elevation from 
antenna height above mean sea level.
    (b) Average terrain elevation shall be calculated using elevation 
data from a 30 arc second or better Digital Elevation Models (DEMs). DEM 
data is available from United States Geological Survey (USGS). The data 
file shall be identified. If 30 arc second data is

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used, the elevation data must be processed for intermediate points using 
interpolation techniques; otherwise, the nearest point may be used. If 
DEM data is not available, elevation data from the Defense Mapping 
Agency's Digital Chart of the World (DCW) may be used.
    (c) Radial average terrain elevation is calculated as the average of 
the elevation along a straight line path from 3 to 16 kilometers 
extending radially from the antenna site. At least 50 evenly spaced data 
points for each radial shall be used in the computation.
    (d) Average terrain elevation is the average of the eight radial 
average terrain elevations (for the eight cardinal radials).
    (e) The position location of the antenna site shall be determined to 
an accuracy of no less than &177;5 meters in both the horizontal 
(latitude and longitude) and vertical (ground elevation) dimensions with 
respect to the National Geodetic Reference System.
[ 58 FR 59183 , Nov. 8, 1993;  59 FR 15269 , Mar. 31, 1994]