AERIAL SURVEY

Evening Post, Volume CX, Issue 151, 24 December 1930, Page 6

AERIAL SURVEY

MAPPING OUT WILDS

BRITAIN PIONEERING THE WAY

News about the progress of aerial survey work in Northern Rhodesia provides striking illustration of the superiority of air photography to ground survey methods. The area photographed from the air comprises no less than 63,000 square miles. Experienced surveyors estimate that had ground methods alone been available the work of mapping this immense territory would have occupied more than ten years. The air-borne camera has completed the photography of the entire area in the phenomenal time of four months. A mosaic of overlapping photographs, some taken obliquely, and some taken Vertically, is providing the basis of detailed; maps, which will be finished and delivered next June —less than eighteen months after the air surveyors began work. From the information thus brought to hand the geologist, the mining prospector, the tax gatherer, the road and railway, engineer, and the power and water experts will be enabled to draw knowledge which will assist them in their diverse tasks. The first step in intensive development of the area, in fact, has been taken by the survey aeroplanes. WORLD'S FIRST SURVEY 'PLANE. 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 between the taking of the first and the last photographs. The speeding-up is largely due to the employment of a specially designed British twin-engined biplane, the first survey 'plane built in the world. An air survey craft should possess uninterrupted view downwards, both vertically and obliquely, so that the camera may be operated from the cabin or cockpit without obstruction from any part of the aeroplane. The pilot must have unrestricted view; on him rests the responsibility of steering the aircraft 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 'plane used by the Aircraft Survey Operating Company for the work in Northern Rhodesia, equipped with two 500-h.p. motors, is able to maintain level flight at a height of 9000 feet on the power 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 in Rhodesia. Actually, the area, the largest ever mapped in a single air survey enterprise, was photographed from c three ground bases only, a feat impossible of achievement without the endurance and safety of the twin-engined 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 Bio de Janeiro and its environs has induced the authorities of Buenos Aires to request tenders for the survey of the great Argentine city and the surrounding territory. . - . . . AIR MAPS OF SPAIN. In Europe the biggest air survey scheme yet attempted is likely to_ > ; begun next year in Spain. The project covers more ths,n. one-half of the total 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 anair survey could be accomplished in a quarter of the time taken by ground methods—the Spanish official calculation 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.