Height Above Average Terrain (HAAT): The height of the centre of radiation of the antenna above the average elevation of the terrain (AET) between 3 km and 16 km at 100 m intervals (in the case of low-power TV, distances from 0 to 5 km should be used instead) from the antenna along a particular radial. AET is calculated based on Geobase 50K Canadian Digital Elevation Data (CDED) 1 arc-second data for Canada, the United States Geological Survey National Elevation Dataset (USGS NED) 1 arc- second data for the continental U.S., and the NED 2 arc-second for Alaska. Determination of HAAT does not stop at the border or over bodies of water. Each HAAT determination shall incorporate the full 3-to-16 km radial segment and shall not be truncated at the border nor over bodies of water.
Maximum Height Above Average Terrain (maxHAAT): The largest of the HAAT values determined for eight standard radials spaced every 45 degrees of azimuth starting from true north.
HAAT in the Direction of the Affected TV Station: The largest of the HAAT values determined for standard radials spaced every 5 degrees of azimuth within an arc of ±22.5 degrees from a line between the WSD location and the closest point on the contour in the direction of the affected TV transmitter.
Above information extracted from DBS-01 at http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf10928.html#s4