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Aviation History
1951
1951 - 0625.PDF
6 April 1951 Yellowknife is typical of the "larger" towns in the survey area. 408 Squadron, consisting of eight long-range Lancaster 10 aircraft, each equipped with three Fairchild F.224 cameras precision-mounted in a single mount. The cameras are tied-in to each other to within 10 seconds of arc, and each camera is jig-drilled to be interchangeable without disturb- ing the calibration. In addition, these aircraft carry William- son Ordnance Survey cameras for vertical coverage. Vertical photography is primarily allotted to No. 414 Squadron, which is entirely committed to this work, although aircraft of No. 408 may take vertical photographs when tri-camera areas are not available. No. 414 is equipped with 14 Dakota Mk 6 aircraft with long-range cabin tanks and a cabin well for a Williamson Ordnance Survey camera. ' Whenever possible tri-camera coverage is obtained before vertical photography is attempted. Although this involves an additional year's delay in producing the maps to the scale of four miles to the inch, it means that much-improved maps become available earlier for use by commercial firms wishing to explore almost virgin territory. The normal day for a photo detachment starts at about 3 a.m., when the duty crew checks the final weather fore- cast and prepares to make a flight to check actual weather. The first aircraft are usually airborne by 5 a.m. j if conditions are clear, the others are called into the air by radio. On an average flight the aircraft is climbed gradually to approximately 10,000ft and the search for clear areas con- tinued at that altitude. In this way a great deal of oxygen is conserved. If and when a clear area is sighted the aircraft climbs to 20,000ft and the crew make final preparations for the photo-line flying. Cameras are given a short test run, the solar navigator (an adaptation of an astro-compass) is set up, and the aircraft is trimmed carefully for straight and level flight. The trips to the operational area are done on dead-reckoning navigation, since existing maps are very in- accurate. A three-course wind is usually found before starting down the first line to give the navigator a course to fly and to help him in checking the end of a line. Once the area is reached the navigator takes over and directs the pilot to the beginning of the first line to be attempted. Turn onto line is done about 15 to 20 miles back from the start of the line shown on the map. The drift is checked carefully and the solar navigator started. Mean- while the camera operator checks the interval and drift on his view-finder and levels the camera. As the start of the line approaches the navigator gives the order to start the camera. On the line the navigator is busy checking drift every ten minutes at least, and making new settings on the solar navigator. In between times he is trying to pick up pin- points and also sketch in on his flight-line map any details which may help him on his next line. The second pilot assists the navigator in map reading while the first pilot is occupied in maintaining the required heights within ± 50ft and holding course to within less than one degree. This calls for intense concentration and not all pilots can measure up to it, especially when flights may last as long as ten hours. Uninviting terrain—and more July ice—photographed on Victoria Island. One of the major problems in the north is maintaining direction. The best magnetic compass becomes erratic in higher latitudes and the vacuum-driven gyros do not stand up very well.- Even gyros corrected for the mean latitude of the operations may go unserviceable and precess excessively after a very short time. The solar navigator is used to direct the pilot for straight-line flying, and the astro compass is used to supply settings for the gyro instruments. Another major problem is servicing the aircraft in the more isolated bases. No hangars or other permanent facili- ties are available at such places as Norman Wells, Yellow- knife, or Coral Harbour, and the work must be done in the open—in rain, snow, or sun as the case may be. Dust is another constant torment to the hard-worked ground crew. Refuelling has to be done from barrels, and even with port- able electric- or petrol-operated pumps this is a long pro- cess. Often the caches are established some distance from the nearest taxi area and the barrels must be manhandled to the vicinity of the aircraft. In spite of the limited facilities remarkable records of serviceability are achieved. One squadron maintained 100 per cent serviceability on twelve aircraft for approximately a month, during which they flew 1,700 hours and photograped 120,000 square miles. Film exposed in the field is shipped to No. 1 Photo Establishment at Rockcliffe for processing. Possessing one of the world's finest and most modern aerial photographic laboratories, this establishment plays a vital part in the overall programme. The exposed roll films are sent in with a full report listing the area covered, weather conditions at the time of exposure, height and speed of aircraft, and other details. The film is put through continuous processing machines for development, and is turned out at the rate of five feet a minute. The negatives are then placed on annota- ting tables with glass tops lit from underneath. Here the film is given an initial check for accuracy and quality, and each negative is numbered to allow instant identification. Possible gaps in the area being covered, caused by camera failures or lack of forward overlap, are spotted at this stage. The negatives are then printed and laid out hi a mosaic. The mosaic shows whether any lateral gaps exist as a result of errors in navigation. The lay-down, as this mosaic is called, is then photographed and, if there are gaps, the detachment which flew the lines is notified and prints of the lay-down are sent out to be used in doing the re-fly. The R.C.A.F. is not responsible for map making. The finished prints are turned over to the Department of Mines and Technical Surveys or the Army Survey Establishment which are responsible for the compilation of maps. The survey programme is primarily for the compilation and correction of maps, but the photographs serve many other purposes. They have proved to be useful in mineral exploration, water-power development, forest and agricul- tural surveys, and town-planning investigations and are made available to both Government agencies and com- mercial organizations.
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