The office technical staff of draughtsmen and computers also became more and more specialised as survey records accumulated and the demand for published maps increased. Expert cartographers were trained to draw maps for publication; computers helped to maintain the efficiency and accuracy of the survey records. After the First World War the staff of the Department of Lands and Survey was employed mainly on settlement surveys for returned servicemen and, until 1935, when the effects of the depression had worn off, no outstanding advances were made in the field of surveying and mapping. The Department had made some efforts in 1911 and again in the late 1920s to carry out observations for the laying down of a geodetic triangulation for the more effective control of topographical mapping, and for linking up the existing local triangulations into one coordinated whole. An organised attack was begun in 1935 and it was completed in 1940. Thus it was possible, during the Second World War, to have a provisional grid for military mapping.

Some advance was being made overseas in the use of aerial photography to help to produce topographical maps, particularly for military purposes. Techniques and equipment were being developed whereby contours and physical features could be plotted down by stereoscopic methods from overlapping pairs of photographs with the minimum of field survey work. In 1935 the Department, through a national mapping committee, began the 1 : 63,360 (1 mile to an inch) topographical map series. The Air Force bought the necessary aerial camera and by the end of 1935 had photographed 500 sq. miles of the Hawke's Bay district. At the same time the Department bought two simple stereoscopic plotters which could plot down topographic detail from each overlapping pair of photographs from survey control points identified on the ground by the surveyor.

When war broke out in 1939, priority was given to the production of maps and charts for defence needs. Most of the professional and technical staffs at head office and in the districts were diverted to this essential work. At the same time the Army hired a private aerial survey company on contract to supply aerial photographs of strategic areas as a basis for detailed topographic mapping. This company still operates under agreement and supplies all of the official aerial photographs. By the end of the war, with considerable help from the Army, 1,500 sq. miles, covering fortress areas, had been mapped on a scale of 1 : 25,000, and 50,000 sq. miles (half the area of New Zealand) on a scale of 1 : 63,360 (1 mile to an inch). In 1947 the full responsibility for the production of military maps and charts and the representation of the armed services at all overseas military mapping conferences was vested in the Surveyor-General.

After the war the Department adopted new equipment and new methods and new techniques in surveying, in aerial photography, in photogrammetry, in cartography, in map printing, and in computing, all of which had been developed and proven by overseas survey and mapping agencies. Some of these developments included the precise measurement of distances by radar; the production of the distortion-free lens for aerial photography; the development of photogrammetric plotting equipment for the precise measurement and contouring of aerial photographs; the use of distortion-free mediums for drawing and type-set lettering for cartographic reproduction; the use of improved photographic processes for plate production for map printing; and the use of electronic computers for involved and high mathematical computations.

Thus the office of the first Surveyor-General at the Bay of Islands in 1840 has grown into the present surveying and mapping organisation which controls and directs all land-title surveys of civil and military topographical mapping and aeronautical charting; triangulation and trilateration for precise survey control; development surveys for land settlement and housing; and special precise and detailed mapping for the planning and location of highways, railways, airports, drainage and irrigation, and hydro-electric schemes.

by Russell Gladstone Dick, I.S.O., formerly Surveyor-General, Department of Lands and Survey.

• Appendices to the Journals of the House of Representatives, Annual Report of the Surveyor-General (C. 1 of each year)
• Descriptive Atlas of New Zealand, McLintock, A. H. (ed.) (1959)
• Catalogue of Maps, Department of Lands and Survey (1959)
• New Zealand Surveyor, (1889– ) (twice yearly)
• N.Z. Institute of Draughtsmen News (1956–60) (irreg.)
• New Zealand Draughtsman (1956– ) (annually).