TOPOGRAPHICAL MAPPING OF N.Z. IS IN PROGRESS

Bay of Plenty Beacon, Volume 15, Issue 70, 17 July 1950, Page 2

TOPOGRAPHICAL MAPPING OF N.Z. IS IN PROGRESS

The difficult but necessary task of preparing topographical maps of New Zealand, which was suspended during the war, is proceeding steadily and during the past few weeks men of the Lands and Sui’vey Department have been stationed in the heart of the almost inaccessible country near the Bay of Plenty. Topographical maps of limited areas of the Dominion have been made from time to time but it was not until there was a grave danger of a Japanese invasion that it was realised how little of this mapping had been done. Use In Warfare

In modern warfare, particularly with the greatly increased use of artillery shooting off maps at invisible targets, the possession of adequate maps of the country in which an engagement takes place is the prime importance and when the Japanese threat became real nearly all the resources of the Land and Survey Department supplemented by servicemen, were pressed into survey. A great part of the North and South Islands was mapped on a scale of one inch to the mile.

These maps do not now meet the peace-time needs of the Dominion, so the Lands and Survey Department is aiming to complete a new series of maps on a scale of 1/25,000. The first task has been to map the vast Rotorua-Taupo district and when this task is completed the maps will be of great value when the undeveloped portions of the area are being opened up. A lonely tent or a beacon on the summit of Mount Tarawera or some other peak, or small flags dotted about the country," are the only clues to the extent of the activity of the party. Selecting prominent, intervisible and suitably spaced heights, a party establishes trig stations. Often these points are reached only after a stiff tramp over unbroken country. Aerial Photographs

Observations with theodolites are made to each trig station and from the data obtained the position and height above sea level of each station is computed. These trig stations are the framework for the compilation of the maps. The trig stations are plotted on a mapping board and with the aid of clinometers, sighting vanes and other instruments, contours, roads, streams, buildings, fences and other topographical features are drawn in to the correct scale.

Aerial photographs are also employed in the production of the maps. By their use a much more accurate and detailed map is possible, particularly over expanses of fern and scrub in the type of country where the surveyors are working at present.