The Chatham Islands Geodetic Datum 1979 (CIGD1979) was defined in 1981 by an adjustment of survey observations and measurements undertaken in 1968, 1970, 1977 and 1979.
It superseded the Chatham Islands Geodetic Datum 1971 (CIGD1971).
The origin of CIGD1979 is defined by the position of the mark Astro Station (geodetic code 5505, (43° 57' 23.60" S, 176° 34' 28.65" W). Orientation is provided by the adjusted azimuth determined by astronomical observations at four stations during 1968, 1970 and 1979. It is defined as 115° 58' 47.03" from Kahunene No 2 (geodetic code BARW) to B Kapangatakahu (geodetic code BARX).
The main parameters for CIGD1979 are summarised below:
|Name:||Chatham Islands Geodetic Datum 1979|
|Reference ellipsoid:||International 1924|
|Reference frame:||Astronomic datum|
In 1998 the NZGD2000 superseded CIGD1979 as the official geodetic datum in the Chatham Islands.