SURVEY FROM THE AIR

Stratford Evening Post, Issue 9, 2 August 1930, Page 2

SURVEY FROM THE AIR

MAPPING IN AUSTRALIA

HOW PHOTOGRAPHY HELPS Tiemendous strides have been made in recent years in aerial survey, and Australia is to reap the benefit, for the Air Force is about to commence a survey of about 500 square miles of land that has wm er h be !. ore i bGCn mapped - Other areas vnl be dealt with subsequently, and it l Jn kely tnat before the end of th e vear 3000 square miles will be surveyed from the air. A considerable amount of this class of vork has already been done by the Australian Air Force, the jobs including ordinary topographical mapping, photographs for the Navy Department, for charting purposes, town surveying for municipal purposes, forestry survey work or oil research at Papua, and the photographing of areas in South Australia to ascertain the geological structure of the earth. The camera used for the work is of a special type which is mounted in the observer’s cockpit in the aeroplane, with the. lens pointing through a hole in the floor. Each picture taken is 7in by 7in and is adaptable for scales of from one m 2000 to one in 25.000. Most of the work is done with the aeroplane at a height of 12.000 feet. The pictures are taken in parallel strips on a film, one of which is sufficient to photograph a total area of nearly 200 square miles. This area can be photographed completely in about two and a half hours. Each ‘picture on the film is an individual one, the outer portions of which overlap a portion of the picture on the previous nlrn This ensures that no part of the territory is left unphotographed. lively picture taken is automatically numbered by the special apparatus in the camera, which also records in the film the height at which it was taken, the levels of the plane, the date, and the tune to the nearest second. This leaves no margin for error when the photographs are being pieced together for the completed mosaic. A special stereoscopic instrument enables contours to be corlectly indicated. The temperature at 12,000 feet is usually about zero, or below and both pilots and photographers have to be expertly trained to carry out the work successfully. The aeroplane has to bo kept on a straight course up and down the area being photographed and must be kept level and at a uniform height.

I Flight-Lieutenant G. Packer, the Air j Force expert on aerial survey work, who I explained the process of operation, said j that flying was not as expensive as was generally thougnt. The cost for conI tinuous operation in aerial survey was about 10/- a square mile. Fie added that a certain amount of ground work was usually necessary for the most successful survey. One of the biggest aerial jobs done recently by the Air Force was the mapi ping of 600 square miles in the vicinity of Sydney. This was done for the local authorities to help them when making sewerage and water connections. The Air Force was paid for the actual cost of the work, and benefited from the experience given the pilots and photographers.