AERIAL SURVEYORS

Dominion, Volume 12, Issue 83, 2 January 1919, Page 5

AERIAL SURVEYORS

■- -.• Aeroplanes have opened a new field for preliminary survey. Whereas in the past millions of pounds and a great amount of time were expended in expolatory survey in bush and timber country by the old methods,, nowadays by means of aerial photography an enormous area of new country may be as accurately mapped aa in:the days'of the theodolite, cliainman, and axeman, in a'shorter time and at less expense. And there will'be the additional advantage of a true; portrayal of the special landmarks on the ground and the taking in of .all intervening country that was only-roughly estimated- in the earlier days. The photographic expert can tell approximately from the light and shade effects / the elevation of contours. The height of prominent ridges, hills, and mountains can be nscortained with suffi-' ciqnt acuracy by flying low over them and taking the altimeter readings on the instrument board of the aeroplane. The pocket altimeter was usually utilised in the old days with no greater accuracy. The method pursued would probably be this: ; A clearing would be made close to the termination of some main dr base survey line. This would serve as an aerodrome. •Here quarters and temporary' hangars would be erected. • . / . 7 Starting from this point, photographic surveys would be taken in some given compass direction oacli day, weather.perFrom theso.main photographio lines, when completed, the interveningareas would be filled in, starting from any desired point on the already prepared photographs, and thus the whole terrain wotald become a photographic map. In all probability the camera would be exposed from a given elevation, thus facilitating the' mapping of distances. Having completed the goneral photographic survey of any one area, the prominent landmarks and high ground Vould/j be selected and their 1 elevation found by the' altimeter' in tho machine, and aiiy special feature could Be noted by low exposures of camera. This would be the part of the . pilot and mechanics. Then-would come tho work of photo-J graph or and draughtsman. Between them they, would .check the ground distances hy means of. old survey lines and. tying-in posts, previously marked so as to be easily distinguishable in an aerial photograph, and any given' known distanco marked: on the ground and photographed would bo a sufficient test of the accuracy of the camera and instruments. It would then only be necessary to make the usual survey map from the. photographic map, and this could bo done at a greatly reduced cost'in labour and time. As civilisation pnshed its w&y into the wild country and .the land was oleared, so could an aciirato ground and geological survey be made.—"R.A.F.," in the "Daily Mail."