AERIAL MAPMAKERS.

Hawera Star, Volume XLVIII, 25 September 1924, Page 9

AERIAL MAPMAKERS.

PROBLEMS FOR NEW ART.

The many fine maps of the war zones made by means of photography from aeroplanes during the war suggested the possibility of superseding the ground surveyor and his theodolite by airmen and the camera, and three years ago the Government appointed a committee to consider this possibility. The committee, however, it is understood, has come to the conclusion that aerial surveys for all purposes are not at present practicable, and that such a method of map-making, except where the- area to be surveyed is flat, is neither -as efficient moo* as economical as the old method. , The excellence of the war maps made from aerial photographs was largely due to the fact that in most cases fairly reliable maps of the regions were in existence, which provided definite points by means of which the air photographs could he joined up. But where, maps pi unsurveyed districts are acquired no such reference points are available. There is also the difficulty of airmen engaged in photographing the ground beneath always keeping at thef same altitude, witlr the axis" of the camera vertical, and maintaining this altitude at something like l'0,000ft: Very satisfactory air -maps have been made 'showing the general features of a country by means of oblique photographs, which embrace a • much lugger area thaii- vertical photographs, and can be taken at very much lower altitudes.'

, But at present no reliable method has been devised, of obtaining accurate air photographs of .hilly country so as to. show the varying ecu tours, and there are few countries so. flat as to provide ideal opportunities fc.r mapping from the aii’. - Some of the finest air maps are those of towns and big . cities. Such, a map has just been completed) of New York, and its suburbs, some 400 square miles, on the generous scale of one inch to 600 ft.) It vis a marvel of detail, and shows clearly everything on the ground below—every street land alley, .each building, whether a- small house or a skyscraper,, every isolated tree and back garden, and all the craft on the river, together. with the varying degrees of oedestrian and vehicular congestion in different- parts of the city. To produce a map of '.his kind, by the-tedious method of the ground surveyor would be practically impossible.: owing to. the ,time arid -Just Hi/oived, and undoubtedly such detailed iir maps of cities would he of very great- advantage to municipal authorities.

Experts' are busy attempting to solve the problems of map-making from the air, so that whatever the nature of the ground it will be accurately and permanently recorded on the aerial, photograph. The problems are partly mathematical, and until they m : e completelv solved the airman-sur-veyor can only give us reliable town -'lans and mans of flat -regions; but he can also obtain fairly reliable maps of lan*? areas at present almost unmapped bv reason- of the difficulty of covering them by the tbeodilite • and the plane-table. Tbri lias already been largelv accomplished in Canada and; Australia, the coastline of Australia being now known with remarkable accuracy as a result of the flight ro”nd the great continent- recently achieved by Winy-Commander Goble cud F 1 vino--Officer MaMntvre. And, as recently detailed in the Observer, air pho'tqgraps of Stonehenge have hewobtained which clearly show the gr°at avenue which fdr over 200 years has beeir completelv obliterated, and was entirely invisible from the ground.