FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1950
1950 - 0720.PDF
FLIGHT THE WORLD IN CAMERA . . . magnetometer, another instrument devised by the Photo- graphic Survey Corporation, Ltd., is used to measure the magnetic field strengths of the area over which it is flown. From readings obtained, it is possible to superimpose over a photographic mosaic map a -' contoured '' map of mag- netic changes, and from this correlated plan the experi- enced geophysicist is able to assess the likelihood of certain minerals being present in quantity. Oblique air photography, as distinct from vertical map- ping photography, is the more spectacular, aspect of air survey. The pictures on pages 466 and 467—only a very small selection from the library of Aerofilms, Ltd.—empha- size the pictorial value of " obliques." But their practical uses are manifold. Factory layout, irrigation, forestry and snow surveys all come within its scope, and for the archaeologist it has shown up many hitherto unsuspected sites. These ancient sites can be made apparent in two ways. One is by photographing an area at a time when the sun is low and the lighting throws small irregularities of the ground into strong relief; by this means some of the most indistinct earthworks can be clearly seen. The second method of revealing these traces of ancient habitation is especially interesting. Wherever man has lived the ground immediately surrounding his habitation becomes more fertile by virtue of his refuse and drainage, and this extra fer- tility lasts for hundreds of years after the man and his home has passed into oblivion. An observer on the ground can see nothing ; but from the air, during the period of standing crops, the outline of the site is clearly laid out in vegetation of a hue (usually darker green) differing Two Williamson products. Left, the Williamson- Ross multiplex equipment for producing con- toured maps from air photographs and, above, the O.S.C. Mark 2 air camera which is one of the most advanced instruments of its kind in the world. It takes a square 9inx9in photograph. from that of its surroundings. During the winter, when there are no crops and the ground is under the plough, not the faintest sign of any sort can be seen, but with the spring and summer growths the effect of the subtle chemical difference in the earth's constituents makes itself apparent from the air once more. It is curious that, despite the increasing importance of air survey through the years, only one true survey aircraft, designed and built specially for the task, should have been produced. This was the Gloster Survey, a twin-engined machine produced twenty years ago for the Aircraft Operat- ing Co., Ltd. A number of conversions and adaptations have been made, and the gallant old Avro Anson has done trojan work ; to-day there are, of course, specialized ver- sions of both the Bristol Freighter and Percival Prince. High performance as such is not necessary, but a high ceiling is very important, as are also good controls. Since flying over vast, uncharted areas is one of the major tasks of a survey aircraft, reliability is an essential. Economy of operation is also just as important as in other spheres of unsubsidized commercial aviation. Long range is re- quired, because the machine may be operating far from its base, and it may be that the nature of the task in hand will require many hours in the air. The ability to operate from unprepared sites is an obvious virtue for any aircraft which is likely to be used in the remote and unpopulated parts of the globe, and amphibious types clearly have their value for some types of survey. The air survey companies of Britain have shown the old-time pioneer spirit and have travelled the world over to carry out many contracts. Those of the Hunting Group all grew from the small beginnings of the first commercial air photographic company, Aerofilms, Ltd., formed in 1919 For map-revision work and photo mosaics correctionf or tilt is made on a special Wild enlarger in which the negative and printing paper are fixed in articulated holders. Below, fitting new photographs on to an existing map. Huntings are busy producing mosaics of London to scales of six inches and twelve inches to the mile.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
