POLAR PHOTOGRAPHY

Hawera Star, Volume XLIX, 8 January 1930, Page 8

POLAR PHOTOGRAPHY

MAPPING FROM THE AIR DIFFICULTIES IN' ANTARCTIC CAPTAIN McKINLEY'S PREPARATIONS (Copyright by Sydney "Sun” and New York "Times.”) LITTLE AMERICA. Nov. 10. The photographic survey during the flight to the South Pole from Little America, will, if successful, make a record of this region which can be returned to civilisation and studied at leisure 'by those who are interested in the formation of the South Pole Continent, (says Captain Ashley McKinley.) Such a survey is difficult because elevations will be constantly changing. The work must be done in cold more severe than is usually experienced at home in a surveying flight, and every moment in the photographer’s time must be utilised to the best advantage.

Such flights are not repeated, and there will be no opportunity to make good deficiencies in the record. Probably no flight ever offered so great an opportunity to demonstrate the value of aerial photography as a surveying method. Here is a, virgin country, a vast unknown plain, upheaved ice showing the presence of land beneath it, and a rampart of mountains, of which almost nothing is known-

" MOSAIC STRIP MAP. We hope all this will be recorded, made into a mosiac strip map and brought back for the geologist, the glaciologist and others to pore over and decipher the meaning of its contours. Aside from the pleasure of flying over such an unknown land there is the pleasure of contributing something new and of vafue and scientific knowledge, even though the one who records it, as in this case, is incapable of interpreting its symbols. As a task it should probably be unique, as there has never been made a single trip map 1600 miles long on one flight. One must keep one’s lingers crossed and hope that nothing jams, for a defect in the mechaniscm of the camera at such a eriticaf time or some other interup.tion would be quite sufficient to impel a harassed surveyer to jump out on the nearest peak and, as our columnists say, end it all. But if everything goes well, it will be a map which in length and content will be new and of great value. It is always rash to predict what may be done in exploration. AIMING OF CAMERA. The camera is aimed through holes in either side of the ’plane, where canvas flaps have been made to fasten around it to keep out. the ic-.v wind. Pictures will be made of one side ol the route going out and of the other coming back if the same route is taken, and as they are taken at an angle they will cover a large territory. / . The photographs wifi be- obliques, taken at 20 degrees from the horizontal and overlapped so as to give a continuous strip from our base, which is on the coast, to the .South Pole, about 800 miles inland. Fbom these photographs additions and verifications- can be mads on the existing fine-maps, or hand-drawn, and a- photographic mosaic can be: constructed. ' .

The mosaic is made of overlapping photographs laid and;pasted on amount or base,on which has been plotted all existing control data. Controls may be defined ns all data used to fix points on which to construct a mosaic or linemap. . ' These data are always related to some point located on the earth’s surface, and an exactly (accurate survey cannot be made with it. The images on each photograph are matched with like images contained on the next nhotograiph slip, in this manner forming a composite picture of the entire area contained in the exposed film. BARRIER DETAIL. The first picture of this long mosaic, we hope, will show the great ice harrier and Little America. Then the strip starts across the harrier. While most of the barrier is flat, there are many rises and depression.?, crevasses' and .sasturgi, all of which will help the glaciologists to. determine the general character of this great sheet of ice and ‘possibly what underlies it. All details will be shown to scale in the aerial photographs. At about 400 miles from the base the glacerised mountains with bare rock extending through the ice will appear in the photographic strip. These photographs will greatly interest geologists. The photographs, taken at 20 degrees from the horizontal, will include the horizon appearing about 12 degrees from the top of each photograph. The length of the area covered on each picture will vary from 42 miles at 1000 feet altitude to 132 miles at 30,000 feet. The flight, as planned, will average about 5000 feet above the surface, so that the strip will cover an area about BUO miles long and 81 miles wide DIFFICULTIES OUTLINED. Exploration aerial mapping is necessarily conducted under much more difficult circumstances than mapping in a civilised country. The polar flight will he especially complicated in this way, as the ’plane will fly at varying altitudes, necessitating a varying time interval between exposures so as to obtain the proper overlap.

In other words, the surveyor must calculate his altitude and make adjustments between each picture, and the intervals between exposures are only two minutes long. To obtain sufficient data to control the maps to be made from the photographs there must be recorded between the exposures the altitude temperature, ground speed, dead reckoning, any observations Commander Byrd makes, and bases laid by the dog teams as they are passed.

Between times one can take a nap or look at the scenery. And, when possible, the hands must be warmed in fur bags fastened to one's legs so as to keep the fingers from becoming entirely rigid. Fortunately the flight passes over Captain Roald Amundsen's did route to the Pole, so that his records of ground elevations can he used to determine approximately, in conjunction with our barometric readings, our height above the earth's .surface. Captain Amundsen’s observations are being checked as far as the mountains by Dr. Laurence Gould of the geological party. The .strips being started at Little America, which is accurately located, and ending at the Pole, the two points will serve to control the ends of the etrip.

ARMY AIR. CAMERA. The aerial camera used on this flight is the regulation United States Army Air Corps camera, containing a long roll of paper for recording data, a thermometer, a barograph, and a stopwatch-

Covers have been attached from the camera. apertures to the ’plane to the cover of the camera to keep out the sub-zero air, which would otherwise come in at 100 miles an hour. These, covers may keep the aerial surveyor from ending up with frozen hands, as most of the work must be done without gloves. Convenient devices have been madein Little America to meet the unusual conditions under which the survey is made. Among them is a stand attached to the camera containing instruments for recording data. This camera contains in each magazine, three of which will he carried, 75 feet of hypersensitised panchromatic film nine inches wide, and takes 110 exposures, -seven by nine inches, on each roll-

The camera is semi-automatic, a crank being turned for each exposure, exposed film being passed into place, a pressure plate released to allow the film to move freely and reset to hold the film in a perfect focal plane. It also sets the shutter. The camera weighs 34 pounds ana is constructed of aluminium. It is made with the same precision as any other surveying instrument. The usual 12-inch focal length lens lias been replaced by one of 91-inch focal length in order that the greatest coverage for the size of the exposed film can be obtained. Three extra rolls of film and a changing bag are being carried in order that oictures can be taken on the return flight. This will make it possible to take 660 pictures during the flight.