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]