AIR SURVEY WORK

Dominion, Volume 29, Issue 150, 20 March 1936, Page 12

AIR SURVEY WORK

Photography of Area in Hawke’s Bay GOOD PROGRESS MADE Good progress is being made with the air survey of 1000 square miles of Hawke's Bay, which has been undertaken by the Lands and Survey Department and the Defence Department, anil the Surveyor-General, Mr. 11. E. Walshe. said yesterday that the actual air photography on the area had been completed. Draughtsmen of the Lands ami Survey Department were now working on the photographs, and the task should be completed in about six mouths. The next district which it was intended to survey by air was that between Kaipara and Auckland. This work would be done from the Royal New Zealand Air Force Base, Hobsonville. whose personnel had carried out the work in Hawke's Bay. Plans had also been made for some work in the South Island. The only other air survey work done by his department was a small area near Nelson, which bad been surveyed and mapped by this means experimentally some years ago

The use of this photographic information has necessitated the draughtsmen of the Lauds and Survey Department mastering a new technique, and working with the mirror stereoscope, an intricate instrument by which the draughtsman can see hiils and valleys in photographs which, when viewed singly, would appear lo depict an area of flat laud. . A certain amount of work has to be done to the photographs by the draughtsman before the actual work is begun. He lias tq determine the plumb point or centre of vertical focus which enables the remainder of the photograph to be interpreted accurately on each exposure and then to mark in the contours, which can be traced from examination of the prints under the mirror stereoscope. Among the departments which require maps and plans that cau be produced by air survey are the Mines Department, the Department of Agriculture, the Forestry Department, the Geological Survey, the Public Works Department, the Lands and Survey Department, and the Defence Department, as well as the Department of Scientific and Industrial Research