§  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]