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Aviation History
1948
1948 - 0579.PDF
1948 FLIGHT 473 complex pantograph type which ITS, except clrift, in one step. the record on the paper ; and (d) in axes due to drift, fn addition, the profile is recorded in curvilinear co-ordi- nates which haVe. to be rectified to rectilinear. An instru- ment can be built of a will correct for ill factors, excep To eliminate drift, it is necessary to return to the base jjne. Base lines \0 be established wilJ va^ according to the area, but for small areas will consist p:rone across the centre of the line of flights. The base line is flown in each direction giving two small profiles. However, during the time of flight, drift will have caused a few gamma difference in the total field at the starting point. It is now assumed that this variation was linear, and the correc- tion is applied to the whole profile. A common datum now exists for the area to be surveyed, and each profile of the flight is corrected to this by identifying the point at which it crossed the base line and joining the profile fo it. It is now a comparatively simple matter to plot the profile on to a good base map, and with this done the geophysicist takes over. Dealing with the question of instrument availability, Wing Cdr. Kendall stated that, in America, at least five instruments are on the market, three types being in actual operational use. He then gave a resume of the work being carried out which, however, represents only a part of the surveys completed. The U.S. Geological Survey have several M.A.D. instruments, and have surveyed 180,000 square miles in the U.S.A. and Alaska. The Geological Survey of Canada have three M.A.D. instruments, and propose to survey in time the whole . Dominion, issuing the data with their geological sheets. The Gulf Research and Development Com- pany have surveyed large areas in Canada with their own instrument on their own behalf, mainly for oil. Two American licensees of Gulf Re- search have, in eighteen months, completed about one million pounds' worth of surveys, mainly for oil companies. This represents at least 250,000 square miles. The largest contract was in the Bahamas, but other large jobs have been done in Venezuela, Colombia, Cuba, the U.S.A. and Canada, and a great deal of further work is con- templated. The lecturer concluded his paper by summarj main reasons for the importance of this ^^ under these headings: Elimination of grou^tnterference: On the ground the record is confusedf*P!filumerous small -*-* anomalies from small and insig- nificant bodies at or near the sur- face. These are eliminated with the airborne in- strument. Depth determin a- tion : With the air instrument, the same - body can be flown over at two different heights, thus enabling the size and depth of the body to be calculated with, reasonable certainty. High accuracy: The airborne instrument is extremely sensitive and, with automatic orientation and vector squaring, can provide profiles which can be read to one gamma. The continuous profile is a great advantage over the spot recordings made on the ground Speed : The normal output per instrument should be 7,000 line-miles per month, or 100 times the speed possible with a ground instrument. Low cost: Given reasonable areas, the cost should be one-tenth that occa- sioned with a ground instrument. Accessibility: witVl Diagrammatic representation of the earth and its magnetic lines of force with Equatorial and Polar strengths. Diagram of aircraft showing towed position of the "bird" and, in dotted line, alternative mounting positions for the M.A.D. unit. the methods de- veloped, no area is inaccessible whether over trees, swamps, desert or water. These several advantages, against which there are no com- parable disadvan- tages, clearly state the very strong case that exists for employ- ing airborne means of geo- physical explora- tion, even in cir- cumstances where the qualities peculiar to the airborne system are not an essential. The lecturer gave it as his opinion that the airborne mag- • netometer is but the forerunner of other airborne geophysi- cal instruments, and observed that promising development is in hand in the U.S.A. and Canada in connection with geiger counters, electro-magnetic surveys, gravity meters and the installation of instruments helicopters. The state to-day is ,t lead, zinc, copper, iron ore and are being consumed faster than they are being located. Geologists claim that these elements exist in abundance, but where easy to locate have largely been found. Thus the work of geophysical exploration is becoming both pro- gressively more difficult and pro- gressively more urgent. It would appear that concentration must be directed increasingly toward the use of physical methods, and of these the airborne schemes would seem to offer the most useful solu- tion. Unfortunately, development in this direction has so far been con- fined to North America, and if the lead British mining com- panies have held in the past is to be maintained, comparable developments should take place in the United Kingdom. \ **" cup . Schematic diagram of detector coils and servo motors housed in the "bird." With • NORTH SEA EXERCISES "C'XERCISES will take place in the North Sea on May 13th-L> and 14th, during which a composite Naval force will be attacked by aircraft and submarines, and submarines willbe located and attacked by aircraft. The forces will include two battleships of the King George V class, H.M.S. Anson andH.M.S. Howe; one fleet carrier (H.M.S. Implacable); one cruiser (H.M.S. Superb); eleven destroyers; four frigates; tensubmarines; and eight Naval air squadrons, comprising about 85 aircraft. In addition, a total of about 50 aircraft ofBomber, Fighter and Coastal Commands of the R.A.F. will take part These will include Lincolns and Lancasters ofBomber Command, Hornets of Fighter Command and Sunder- lands and Lancasters of Coastal Command. , The attacking—"Blue"—forces will be controlled fromArea Combined Headquarters at Pitreavie, Scotland, and will be under the command of Admiral Sir Frederick H. G.Dalrymple-Hamilton, K.C.B., Flag Officer Commanding Scot- land and Northern Ireland, aud Air Vice-Marshal E. J. King-ston-McCloughry, C.B.E., D.S.O., D.F.C., Air Officer Com- manding No. 18 Group, Coastal Command. The defending—"Red"—forces will be commanded by. Flag Officer Com- manding 2nd Cruiser Squadron. The Senior Officer Submarineswill be in command during an exercise involving only sub- marines and aircraft.The area covered by the two-day exercises will be roughly between the Orkneys and Stavanger, on the Norwegian coast(56 to 60 degrees North. 1.5 degrees West, 2.5 degrees East). After the exercises the ships will proceed to home ports.
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