AERIAL SURVEY
% STRIKING ADDRESS
SPEEDY AND SOUND
VISION OF AN EXPERT
(From "The Post's" Representative.) ••.■.:••:'. • ..LONDON, January 26. .Considered figures of tie cost of aerial survey;: and mapping"■ in uncharted re^i°H °Ohe world which were cited in an important paper read before oil technologists in London provide indisputable" evidence—based on years'of experience—of theV'.air-borne- camera's superiority to all methods of ground survey. Not only is the aerial system incomparably speedier, it is also far less expensive than employment of ground expeditions; further, the time saved means that territory surveyed may be developed, and opened up to commercial enterprise at an earlier date, with consequent incalculable gain to the prosperity of the regions affected.
Major H. Hemming,' the author of the paper, one of the world.'s leading authorities on air survey, has directed in the field many thousands of hours of photographic flying. He- is taking a chief part in the negotiations which may lead to the adoption of a. comprehensive scheme for an aerial mapping of the Empire—four-fifths-of which is at present inadequately charted, if at all—and he looks to see the survey aeroplane recognised all over_ the world as the .only practical vehicle for- sur-' veyor,. cartographer, and engineer. He recalled that tho Aircraft Operating Company and the Air Survey Company—both British companies—had accomplished between them the bulk of this work yet undertaken in the Empire, with the exception of Canada, where aerial survey is a Government activity. The companies mentioned have made photographic and reconnaissance; surveys in Africa, India, Bui-ma, Irak, and ; Latin. • America aggregating 200,000 square-miles in area. All of this work was done without any artificial support from Governments in..-the'shape of subsidies. In Canada, where exceptionally quick, and simple methods of air photography may be employed because of the flatness of most of the territory surveyed, approximately 400,000 square ■ miles has been mapped from the air. THE METHODS ADOPTED. Major Hemming described the two methods of , photographic surveying, •which differ in the "angle of attack" of the camera. Most informative —and essential in all but flat country—is the method in which all' photographs are taken as near t^ie vertical as possible, providing a true vertical map of the . ground flown over. Pictures are taken from a height of 10,000 to 15,000 feet, according to the scale required and the lens useq\ Successive photographs arc arranged to overlap each other fore and aft to the extent of 50 or 60 per cent, and laterally by about 20 .per cent. The overlap, enables that part of the Srea common to two photographs to-be ■ examined in a stereoscope; which shows the ground.standing out in perspective and affords the geologist with' an efficient means of viewing detail of ground structure. . .'. . Very accurate flying is. essential in aerial survey. The aeroplane-; must be maintained in flight at constant height and speed, and kept in perfect - trim. Course must be followed without deviation; here gyroscopic, /control of the kind afforded by that remarkable -British device the "automatic pilot" has recently given, excellent results in serVice". •-":-";.'••-•■■"■■■■;•■■ :V f-;-«iis:-.^! ";i.;:; r-yj Vertical mapping is employed when the scale sought is up, to 1 in 50,000, and is essential in many kinds of aerial jwork, such as might:be done for■ oil pipe-line construction. ..'■ The alternative method-—oblique photography—is feasible when: the country/.to be mapped is relatively flat and small-scale maps are sufficient. /The oblique photography is' easy to read, because it/provides, a view similar to that obtained from a-high1 hill.. . ••■V-l;-;/> ■ , LARGE AREAS RECOMMENDED. Major Hemming declared that the maximum benefits of this fascinating : method of locating the Empire's hidden secrets can be secured only, if; really large areas are surveyed. Aerial photography can be completed so ■ .'quickljr that'only a comparatively few aircraft are required for survey of the largest possible territory anywhere in tho world. The flying machines slionld be located at suitable bases and sent from the site of one contract ,to another—in order to take advantage of weather, which ' plays' ,'a most important part', because clear skies are essential if good, clear pictures 'are toVbe'obtained. A few hours' flying may.provide enough material for several months of mapping wort on the ground; iplainly, ■ 'as he pointed out, the, existence of a sound co--ordination " scheme would enable ' sur-: -vey aeroplanes '.to? be switched from one area to another as dictated by weather Conditions, and avoid' piling up -cost in periods of enforced idleness on the ground. He cited the example of the ' Northern-Khodesian survey; tho entire "vast area was photographed in fifty: flying hours, leaving the aeroplane avail■able for other work,' but the rest of the work on the ground took fifteen months to finish. ■ ' : Tackling big areas much reduces the cost. The Khodesian; survey cost only £1 a square mile, and took only eigh4een months, though the company had . to do all the work, including making the maps and laying down astronomical control. A comparative figure for the cost of ground survey in such country cannot be given; there is no doubt that ground methods would have been .prohibitive both in time and "cost. FALSE ECONOMY. . Major Hemming added: "One of the greatest advantages of air surveying, that of speed, has curiously enough proved to be one of its greatest handicaps. The survey may bo completed so. rapidly by '■■ air methods that payment may'have to ; ;be made within, say, two years, instead 6f perhaps sis years if groundl methods- bo employed. As the former may cost a third of; the latter, the fact that a largbr amount of money may be required within the two years' period has prevented contracts being got., This is false economy, which unfortunately is very prevalent today, and is holding up development, of benefitito the Empire and to trade." Addressing himself directly to oil men,-Major Hemming suggested many ways in which aeroplanes might be used to advantage in the administration and working of oilfields. Carriage of drill-, ing machinery and casing in twentyfour lengths to otherwise inaccessible regions, transport of workmen and engineers, fighting oilfield fires by a system of air-borne fire-fighting equipment, and conveyance of medical officers and dangerously sick men were among them. He added that the modern light aeroplane, cheap to run and easy to handle, might be used to great effect by the geologist and engineer, or by the executive officer engaged on oilfield work. Many different types of British aeroplane are employed nowadays on aerial survey, ranging from modified singleengined light craft tffbig 1000 h.p. twinengined biplanes specially designed for the work. In this sphere of aerial activity the British designer was again in the van of progress; the first real survey aeroplane in the world was built in a British factory, and was employed to •signal advantage on the big Northern Hho.desian survey.
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Bibliographic details
Evening Post, Volume CXV, Issue 60, 13 March 1933, Page 5
Word Count
1,119AERIAL SURVEY Evening Post, Volume CXV, Issue 60, 13 March 1933, Page 5
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