Arctic Mapping B

404 PHOTOGRAMMETRIC ENGINEERING ARCTIC MAPPING B. W. Waugh, Surveyor General, Department of Mines and Technical Surveys, Ottawa, Canada SYNOPSIS heen plotted, and 150,000 sq. miles have Present program of tricamera reconnaissance been controlled for contouring; 30,000 sq. mapping; difficulty of sparse horizontal con miles remain to be photographed. trol; the rigid camera mount an aid to ac The plotting is carefully done and the curacy; ice photographs used in bridging water resulting planimetry is of a higher order gaps; radar photographs used in extending than reconnaissance. Working sheets for control; interpretation; contouring by radar special field purposes, as geology, are altimetry; locating isogonic lines; topographic made at suitable scales as required. mapping. CONTROL This paper deals with the actual prep aration of the maps of the Canadian Arctic. As the mapping progressed northward To meet the insistent demand for aero the astronomical control points became nautical charts during World War II, all more scattered and the regular 60 mile the mapping material available was as spacing stretched to as much as 300 miles. similated into complete coverage of Can In the north Arctic Islands' an area of ada at the one inch to eight mile scale. The 300,000 square miles has only 17 reliable map sheets developed in the Arctic were ground control points, whereas conven found to be highly unsatisfactory and in tional plotting requires about one hun complete. In general they consisted of dred. Under these conditions advantage small areas of exploratory sketches, here must be taken of all favorable appliances say topography in broken line, and large and circumstances conductive to accuracy. blank spaces. There was no information THE RIGID CAMERA MOUNT concerning relief. Probably the most important of the ap PRESENT PROGRAM pliances is the rigid camera mount de· The present program, initiated in 1944, scribed by W IC Ross. Plots resulting from comprises complete coverage by adequate its use are not only more accurate but the aeronautical charts at scales of 1 inch to speed with which they are produced is 8 miles and 1: 1,000,000 (1 inch to 16 increased by about ten per cent. The in miles, nearly). Larger scaled maps are creased accuracy is particularly effective surveyed from time to time as required by when the distance between control points civil development or military needs. It can is great. reasonably be anticipated that it will The constant known relationship of the eventually be necessary to cover the Arc cameras is an aid in strengthening plots tic with contoured maps at a scale of where data are missing due to clouds, 1:250,000 or 1 inch to 4 miles. water or snow. THE AEROl'AUTICAL CHARTS ICE PHOTOGRAPHS The planimetry for the aeronautical Ordinarily there is a difficulty in tying charts is extracted from tri-camera or tri the plots of islands together because of the metrogon air photographs; the contouring water gaps between,them. The intersection is from radar altimetry control. The method generally used is never very satis 1: 1,000,000 series conforms to the well factory and the errors in it increase with known ICAO index and specifications. the distance and multiply with extended The one inch to 8 mile charts, Canada's systems. In the Arctic Islands, as W IC version of the 1: 500,000 scale, are in the Ross has explained, advantage is taken of National Topographic Series Index and are the ice by photographing it when it is on a transverse mercator projection. The sufficiently melted to form water pools general practice is to plot details to suit which may be identified from photo to the 8 mile scale and make deletions and photo. Accurate plots may be made for adjustments at the manuscript stage for there are no changes in relief, and, with a the 1 :1,000,000 scale. Over 60 percent of the constant photographic height, a constant 11 million square miles of the Arctic has scale. PANEL ON ARCTIC MAPPING 405 RADAR PHOTOGRAPHS have been used to test and correct the scale of the plots. Radar photographs taken by the U.S.A.F. have proven to be of great help MAGNETIC MAPPING in bridging gaps between controls. The Isogonic lines 'are essential to aeronauti method adopted is to mosaic the photo cal charts. Since 1943 the Dominion Ob graphs using common image points pricked servatory has established magnetic sta on the overlap between carefully selected tions on all the main islands of the Arctic pairs. Photos at a scale of one inch to 15 Archipelago and the contiguous mainland. miles using a range of about thirty miles There are now over 400 stations north of per photo have given good results. A test 60 degree latitude. The position of the over a 250 mile strip gave a maximum north magnetic pole area has been deter error of 1 mile. A circuit 640 miles in mined by stations which completely sur length tied to three astronomic fixes was round it, and a check of its movement is used to control the north end of Baffin maintained by two magnetic observatories Island. Photos have also been used to in the Canadian Arctic. establish the relationship between some of the Arctic Islands. They are, of course. LARGER SCALED MAPS used only when no more accurate means In the 1930's several uncontoured one is availahle. inch to four mile map sheets within the Canadian Arctic were mapped with oblique INTERPRETATION photography by the perspective grid or 'Generally, with the exception of marsh Canadian Method. and low flying indefinite coast lines, the There is now no set program for one interpretation of topographical features inch to four mile mapping or larger. How for the one inch to 8 miles scale is not dif ever it can be expected that contoured ficult. In the exhibit you wi·ll find photo maps of a considerable part of the .Arctic graphs illustrating the terrain of the new will be required at a scale of 1 inch to 4 Prince Charles Island in Foxe Basin, the miles or 1: 250,000. Photography will be large meteoric crater in Ungava, odd fea vertical. It will necessarily be spread over tures on MellviIIe and Ellef Ringnes, Is a considerable period of time because the lands which look like volcanoes, and some photographic weather each year is very strange land formations lying off shore short and because of other difficulties. from Ellef Ringnes and Borden islands. An operation carried out this past sum mer may indicate one method to be used CONTOURING in establishing horizontal' control. The No elevations established by conven position of a photographic plane in flight tional means are available to control con was determined by electronic measure touring. Using the sea as a bench mark ments from tri-lateration stations previ elevations are established by airborne ouslyestablished. In this way the positions radar altimeters in straight lines sixteen were determinedof the ground plumb points miles apart. In an experimental flight with of photographs taken along east-west the altimeter a profile 440 miles in length flight lines spaced at 20 minutes in latitude between control elevations has been made. and north-south lines spaced at one degree Eighty per cent of the water elevations in longitude. An area of about 60,000 established were in error less than 20 feet square miles was controlled. and eighty per cent of the land elevations In many areas the only means of ob less than 30 feet. This accuracy is suf taining vertical control will be by radar ficient to control 500 foot contours, and altimeter. Local distribution of elevations there is no known reason why the lengths may be undertaken by the helicopter of flights cannot be greater than 440 miles. aneroid combination. No accurate eleva There should, therefore, be no technical tions are available for use at larger scales. difficulties in obtaining complete coverage Mapping photography may be from an by taking full advantage of the long sea altitude of about 35,000 feet. inlets of the Arctic. On the small number of tri-camera CONCLUSION flights on which radar altimeter profiles The foregoing is based on present day have been recorded the camera heights knowledge and practice. The discoveries 406 PHOTOGRAMMETRIC ENGINEERING and developments of tomorrow may radi International Congress of Photogram cally change the picture. For one thing metry in September of last year. Mr. the effect of radar altimeter measure Blachut is continuing his investigation. ments on photogrammetry is not fully Developments along other lines are prob as-sessed. Dr. Lyle G. Trorey touched on ably in the making. At any rate it seems the subject in his paper before your Soci safe to say that before the Canadian Arctic ety on January 11,1950. Mr. T. J. Blachut is completely mapped, mapping processes of the National Research Council, Otta will be much simpler than they are today. wa, gave a paper on the subject before the MAPPING IN THE ARCTIC* Gerald FitzGerald, Chief Topographic Engineer, U. S. Geological Survey SYNOPSIS move its important trading post 50 mile" This paper discusses briefly the mapping and up the Porcupine River. Two more moves charting of Alaska from 1898 to the present and ten years later the post was finally time. It emphasizes the development of meth established on the 141st meridian. ods and techniques used principally by the In 1881 the U. S. Signal Service estab Geological Survey in conducting Arctic map lished a meteorological and magnetic sta ping operations, with special emphasis on the tion at Point Barrow where observations use of Trimetrogon coverage combined with earlier planetable surveys to produce the were made for longitude and latitude.

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