AERIAL SURVEY WORK

Hokitika Guardian, 7 January 1931, Page 2

AERIAL SURVEY WORK

TRIUMPH OF PHOTOGRAPHY.

LONDON December I t

News about the progress of aerial uirvey work in Northern Rhodesia provides striking illustration of tile superiority of air photography to ground survey methods. The area photo graphed comprises no less than 63,000 square miles. Experienced surveyors estimate that had ground methods alone been available the work ol mapping this immense territory would have occupied more than ten years. The air-borne camera lias completed the photography of the entire area in the phenonu mil time of four^, months. A mosaic of overlapping photographs, some taken obliquely and some vertiaily, is providing the basis of detailed maps, which will be finished and delivered next June—less than eightteen months after the air surveyors began work. From the information thus obtained, geologists, mining prospectors, tax-gatherers, road and railway engineers, and power and water experts will be enabled to draw knowledge to assist tlieili iii their diverse tasks. The first step ill intensive development of the ui'ell, in fact, has been token by the survey aeroplanes. FIRST SURVEY AEROPLANE.

The time occupied to picture an area of this size is unusually short even in the annals of air survey. Two years might reasonably have elapsed oetween the taking of the first photograph and the last. The speeding-up is largely due to the employment of a specially designed British twinengined biplane, the first survey areoplane built in the world. An air survey craft should possess uninterrupted view downwards, bot.i vertically and ohliquly, so that t..e camera may be operated from the cabin dr cockpit without obstruction from any part of the aeroplane. The polit must have unrestricted view; on him rests the responsibility of steering aircrilft, accurately up and down over the strips of country photographed, immunity from forced landings, especially in desolate or little known territory, is desirable. The British survey aeroplane used by the Aircraft Operating Company in Northern Rhodesia, equipped with two 500 li p. motors, is able to maintain level flight at a height of 9000 feet on the powera of one engine alone. On full power the machine climbs rapidly to 20,000 feet and can fly there for as long as seven hours at a time without descending to re-fuel. This quality Of endurance makes possible the survey of an area of no less than 30,000 square miles from a single ground base; thus is explained the speed of the work accomplished. Actually the area, the largest ever mapped in a single air survey enterprise, was photographed from three ground bases only, a feat impossible of achievement without the endurance and safety of the twin-engin ed machine.

British aircraft are to-day surveying large areas of South America, Africa, Canada, India, Burma, and Australia. In South America the successful British survey of Rio de Janerio and its envirous has induced the authorities oi Buenos Ayres to request’ tenders for the survey of the Argentine city and the surrounding territory.

AIR MAPS OF SPAIN. In Europe the biggest air survey scheme yet attempted is likely to be begun next year in Spain. The project covers more than one-hali of the totai area of Spain and is to be employed for the production of maps on which to base the incidence of land tax on all property. It is estimated that an air survey could be accomplished in a quarter of the time taken by ground methods—the Spanish official calculations allots ten years to air survey and forty or fifty to the ground surveyors. Spanish departmental officials have discussed the scheme with British aerial survey experts in London. A report is being prepared for submission to the Spanish Government, and a meeting to decide final plans will, it is expected be held in Madrid early in the New Year.