FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1922
1922 - 0556.PDF
/ SEPTEMBER 28, 1922 MAP-MAKING AND AERIAL PHOTOGRAPHY Canada's Use of the New Method ALTHOUGH it is realised that rapid and excellent work can be dime by taking vertical photographs and, piecing the separate exposures together, thus obtain a photographic map of any town or district, the speed and accuracy which this new method, opened up by the advent of aircraft, can give is, perhaps, less generally appreciated. In this connec tion it would be difficult to find a better example than the accompanying hydrographic chart and aerial photographic mosaic of the same are*, the St. Lawrence River and canals in the vicinity of Cornwall Island, showing the town of Cornwall, Ontario. From the General Progress Report of the' Air Board of Canada, covering a period of six months (from October 1, 1921, to March 31, 1922), we quote the following notes :— " Attached to this report are two illustrations showing comparisons between mosaics and maps made from actual cellent, and so closely did the prints from the original negatives match that no rectification of the individual negatives was found necessary. This shows that .under good flying condi tions and with careful and skilled piloting remarkably accurate results can be obtained. " Owing to constant changes in light and shade on the water surfaces, due to ripples caused by the varying winds, passing watercraft and other natural conditions, it was found impossible to obtain even matching in texture of the pictures forming the mosaic over such areas. To obviate the patchy appearance due to this, the water areas were brushed over so as to give a uniform texture. With this exception the mosaic was made direct from prints off the original negatives without retouching or rectification of any kind. " The possibilities of time and labour saving in map-making can readily be seen from the comparison. Aerial surveying A comparison between an aerial mosaic and a hydrographic chart of the St. Lawrence River and Canals in the vicinity of Cornwall Island, showing the town of Cornwall, Ontario. The mosaic and chart are ti the same scale, and cover an area of over 10 square miles. The comparison will indicate the accuracy with which topo graphical detail is revealed in aerial photographs and the possibilities of their use in the revision of existing maps. The taking of the photographs in this instance (140 exposures in all) required but a single flight of 2J hours. ground surveys. The maps used in this case are charts made by the Corps of Engineers of the United States Army and issued by the United States Lake Survey Office. Probably no more accurate mapping and finer reproduction could be chosen for comparison purposes. The mosaics were made during last summer by the Air Board for the Canadian Section of the International Joint Commission for use in connection with their report on the St. Lawrence Waterway project. The detail in both suffers somewhat from repro duction and the reduction of scale. This is specially so of the mosaic, as it has had to be re-photographed several times with consequent loss of sharpness in detail. " The pictures were taken from a D.H.4 aeroplane, at an altitude of 8,000 ft., with a K.i film camera made by the Eastman Kodak Company, flown from Ottawa Air Station by Flight-Lieut. H. L. Holland. The flying conditions were ex- H H Senior Officers' School ARMY ORDER 308, just published, states that the following are among the officers who have attended the 9th Course at the Senior Officers School, Woking, from May 26 to August 18, 1922 :— R.A.F.—Squad-Leader H. J. F. Hunter, M.C., and Squad.- Leader A. J. Butler, M.C., A.F.C. by photographic methods is being rapidly developed, and scientists in many countries are working on the development of maps, accurate to scale and elevation, from oblique and vertical aerial photographs. Mosaics such as are shown here do not pretend to absolute accuracy, and cannot at present take the place of maps made from ground surveys. They are rather supplementary to them, giving an actual reproduction of the terrain as it exists, and showing it in much greater detail than the most carefully made map can do. " Provided a series of points, recognisable from the air, were fixed on the ground along a stretch of country of which a map was required, the whole of the detail of the map could be transferred from vertical aerial photographs taken and the laborious process of traversing the whole could be dispensed with." E 13 Pilot's Rescuer Rewarded THE Board of Trade, on behalf of the Air Council, have awarded a gold watch to William Thomas Hawkins, Rescue Boatman of Forth Bridge, and £5 each to his assistants, Richard Marshall and John Allan Ritchie, in recognition of their services in rescuing a flying officer who fell into the Firth of Forth in his Sopwith Camel, on May 29 last. 556
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
