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 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  ±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]