§  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]