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Calculation of Effective antenna heights(eff_hgt) using the SRTM3 Terrain Database

version 1.0
Data is available for America, Eurasia and Africa up to 60 degrees North only. Data holes were filled by interpolation or with DTED0 data.
To ensure proper results, please enter degrees, minutes and seconds as shown below. Leading zeros are not required.
Longitude (ex: 281836) latitude (ex: -152512) Antenna height (ex: 150)
East/West = /- North/South = /- meters agl
EFFHGT is the effective height of the transmitting antenna, which is the height of the antenna above terrain height averaged between distances of 3 to 15 km in the direction of the receiving antenna. In the absence of effective antenna height data, the values resulting from this query can be pasted into T01/T02 electronic notice forms.
The effective height of the antenna above average terrain (EHAAT) is the average of the antenna heights above the average terrain (HAATs) for eight radials spaced every 45 degrees of azimuth starting with true north. The height of the antenna above average terrain (HAAT) is the height of the centre of radiation of the antenna above the average elevation of the terrain between 3 to 16 km from the antenna for each radial. EHAAT is only used locally in Region 2.
Image below is for info only.
Projection information for each data file in SRTM3.
Projection Geographic (latitude/longitude)
Datum WGS84
Zunits Meters above mean sea level
Hunits 3 arc-seconds of latitude and longitude
Spheroid WGS84
Original code fromGreg Hand of NTIA/ITS:
SRTM3v2 data from USGS:
Code modified by D. Botha; Web version 1.0 by J.-M. Paquet 060518.
comments to: manara @


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Updated : 2003-04-14