Kōrero: Modern mapping and surveying

Whārangi 4. Mapping and surveying, 1950–1980

Ngā whakaahua me ngā rauemi katoa o tēnei kōrero

From the 1950s, with growth in areas such as road making, dam building and forestry, other government departments established their own surveying branches. They also needed base maps, which were most often provided by the Department of Lands and Survey.

The introduction of the metric system in 1969 initiated a new map projection for New Zealand, the New Zealand Map Grid (NZMG). Previously, both islands had been mapped onto separate projections – the NZMG provided one projection for the whole country. A new series of large-scale topographical metric maps (NZMS 260) was also begun, with the first (T12 Thames) published in 1977.

West Coast primary triangulation

No further work had been done on New Zealand’s primary triangulation in the 1950s and 1960s, except for replacing a station that had been destroyed by erosion, Muarangi (near Dargaville), in 1958. The 1970s saw increased interest in the West Coast of the South Island for forestry and hydroelectricity, and it was decided to extend the first-order net over the north-western coast. New technology, such as helicopters for flying teams in and out of stations, and electromagnetic equipment for measuring distances, meant the extension took only two months to complete in 1974.

White ghost of the coast

In 1949 the Royal New Zealand Navy embarked on a programme to re-survey the coast and harbours, as many of the existing charts were at least 100 years old. No-one in the recently formed navy had survey training, so the Australian and British navies provided trained officers to get the programme started. The Australian navy leased a survey craft to New Zealand, HMNZS Lachlan, which became fondly known as ‘the white ghost of the coast’. In 1960 W. J. L. Smith became the first New Zealander to take command of the vessel and the survey.

Mosaic maps and orthophotos

Aerial photos cannot be used directly for maps because of distortions caused by the curvature of the earth, the angle of the camera and the topography of the land – especially on rugged terrain, common in New Zealand. However, the New Zealand Mapping Service did issue a number of mosaic maps from 1944 onwards, not as replacements for topographical maps, but to assist planning for development. The series NZMS 3 eventually provided extensive coverage of New Zealand, especially the North Island, with the last sheet being published in 1982.

Orthophotos, on the other hand, are aerial photos that have been corrected to remove the distortions. They can then be overlaid with map data (such as property boundaries) to combine the visual information of a photograph with the detail of a map. They are particularly useful for large-scale engineering projects and town planning. The techniques of creating orthophotos were developed in the 1960s, and the first area of New Zealand to be covered by orthophoto maps was the Clutha–Alexandra valley in Central Otago, in 1978–79. This was at the request of the Ministry of Works and Development, which was then planning the Clutha Dam. In 1977 the Department of Lands and Survey bought a computer system to produce orthophotos.

Me pēnei te tohu i te whārangi:

Melanie Lovell-Smith, 'Modern mapping and surveying - Mapping and surveying, 1950–1980', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/modern-mapping-and-surveying/page-4 (accessed 8 May 2021)

He kōrero nā Melanie Lovell-Smith, i tāngia i te 24 Nov 2008, updated 17 Aug 2018