Height Above Average Terrain

This worksheet may be used to calculate your repeater transmitting antenna’s Height Above Average Terrain (HAAT). This data must be supplied in order to properly coordinate your repeater.  Using the FCC HAAT calculator below is a much quicker, accurate means of determining HAAT.  The instructions below can be used as a means of understanding the concept of HAAT.

FCC HAAT on-line tool

For the FCC HAAT calculator, click here or here’s an older version.
NOTE: The FCC calculator uses meters, not feet.

Information Needed:

  1. Exact Station Location (Be sure you convert GPS readings to Degrees, Minutes, and Seconds. NO decimals!):
    2.   ______ Degrees  ______ Minutes ______ Seconds  North Latitude
  ______ Degrees  ______ Minutes ______ Seconds  West Longitude
  2. Transmit site ground elevation above sea level: ________ Feet
  3. Height of center of antenna above the ground: ________ Feet
  4. Antenna Make and Model: ______________________________________
  5. Identification of topographical map used: ____________________
  6. On the topographical map, plot 8 radials at 45 degree increments, centered on the transmitter location. Then plot 5 circles at 2-, 4-, 6-, 8-, and 10-mile radii, centered on the transmitter location. Determine the ground elevations at the 40 points of intersection of the 8 radials and 5 circles. Enter these into Table I. (See Figure 1 at the bottom of this document).
    7.                             Table I
+--------------------------------------------------------------+
|              |                          Radial               |
|  Circle      +-----------------------------------------------+
|  Radius      |   0 |  45 |  90 | 135 | 180 | 225 | 270 | 315 |
+--------------------------------------------------------------+
|  2 miles     |     |     |     |     |     |     |     |     |
+--------------------------------------------------------------+
|  4 miles     |     |     |     |     |     |     |     |     |
+--------------------------------------------------------------+
|  6 miles     |     |     |     |     |     |     |     |     |
+--------------------------------------------------------------+
|  8 miles     |     |     |     |     |     |     |     |     |
+--------------------------------------------------------------+
| 10 miles     |     |     |     |     |     |     |     |     |
+--------------------------------------------------------------+
  7. Determine antenna height above sea level:
    8. Transmit site ground elevation:          ____________ feet
Add antenna height above ground:        +____________ feet
Equals antenna hieght above sea level:  =____________ feet
  8. Determine average ground elevation:
    9. Add the ground elevation of all 40 points in Table I:  ________
Divide by 40                                            /  40
Equals average ground elevation                       =________
  9. Now calculate antenna HAAT:
    10. Antenna height above sea level:    _________
Minus average ground elevation: -  _________
Equals antenna HAAT:  =  _________

    Figure 1:

    Image