Chatham Islands Geodetic Datum 1979 (CIGD1979)

Chatham Islands Geodetic Datum 1979 (CIGD1979) was previously used to define positions on the Chatham Islands. New Zealand Geodetic Datum 2000 (NZGD2000) is now the official datum used in the Chatham Islands, superseding CIG1979 from March 1998.

Chatham Islands Geodetic Datum 1979 (CIGD1979) was the official geodetic datum used in the Chatham Islands until March 1998. CIGD1979 had itself superseded Chatham Islands Geodetic Datum 1971 (CIGD1971). CIGD1979 was a horizontal datum, providing a consistent 2-dimensional position for a coordinate in the format latitude (Φ) and longitude (λ).

A geodetic datum is a reference system that defines how positions are represented. This includes:

Chatham Islands Geodetic Datum 1979 (CIGD1979) was used from 1981 to 1998 when it was replaced by New Zealand Geodetic Datum 2000. The origin of CIGD1979 was defined by the position of the mark Astro Station, with the geodetic code 5505. The orientation of the datum was established through astronomical observations at 4 stations during in 1968, 1970 and 1979. It was defined as the observed angle of 115° 58' 47.03 between Kahunene No 2, geodetic code BARW, and B Kapangatakahu, geodetic code BARX.

Key parameters for the Chatham Islands Geodetic Datum 1979.
NameChatham Islands Geodetic Datum 1979
Coverage areaThe Chatham Island group between 177.54°W – 177.25°W and 43.3°S – 44.64°S
EPSG code6272
Coordinate systemGeographic
Reference frameAstronomic datum
Reference ellipsoidInternational 1924
Prime meridianGreenwich
Deformation modelN/A
Reference dateN/A