Sec.  80.759   Average terrain elevation.

   (a)(1) Draw radials from the antenna site for each 45 degrees of azimuth
   starting with true north. Any such radial which extends entirely over land
   from the antenna site to the point of +17 dBu field strength need not be
   drawn.

   (2) If the distance from the antenna site to the point of +17 dBu field
   strength  between any of the 45 degrees radials would be less than the
   distances calculated along these radials, an additional radial between such
   adjacent radials must be plotted and calculations made in each case. Each
   additional radial must be that radial along which it appears by inspection
   that transmission loss would be greatest.

   (b) Draw a circle of 16 km (10 statute mile) radius using the antenna site
   as  the  center.  Divide each radial into 320 meter (0.2 statute mile)
   increments inside the circumference to the 3.2 km (2 statute mile) point.

   (c) Calculate the height above sea level of each 320 meter (0.2 statute
   mile) division by interpolating the contour intervals of the map, and record
   the value.

   (d) Average the values by adding them and dividing by the number of readings
   along each radial.

   (e) Calculate the height above average terrain by averaging the values
   calculated for each radial.

   [ 51 FR 31213 , Sept. 2, 1986, as amended at  58 FR 44953 , Aug. 25, 1993]