SURVEY BY CAMERA

Evening Post, Volume CXXII, Issue 21, 24 July 1936, Page 11

SURVEY BY CAMERA

AM -EYE ON PROPERTY THE RATEPAYER PAYS A move has been made by the Wellington Ratepayers' Association towards a poll of ratepayers upon the question whether Wellington should not now change its system of rating from the unimproved value basis <land only) to the annual or capital basis (upon the value and rental value of buildings). If Wellington does decide upon a change—which is always a possibility, as it is in the nature of human understanding and partial understanding to vote for a change just because it is a change—the present- valuation rolls will go to the discard, at least temporarily, and new rolls will be prepared. ■:■-■■ A recent issue of "Flight," an English aviation journal, describes the new technique of checking rolls for annual value assessments, in. which every addition to buildings and offices is counted in as deserving of another little addition to the demand of the rate notice. . Today it is done from the air by quite a few municipalities. In the old days, says the article, a couple of men came along with chains or rods, poles, or perches, a telescopic high-water level, and a funny little telescope, with' which they kept peeping at one another. They walked round the house, trod on the geranium that Aunt Fanny gave you, and departed. The eventual outcome was a large-scale map and the extension to the dining-room-became known to the rating authorities. " Now/all is different. -An aeroplane I passes over, a shutter'clicks, a photograph is taken, and the job is done, AH over the country, authorities, local and otherwise, are using air-made maps.- ■ '"■■ "•■■. With the enormous growth of urban districts it is impossible for the existing maps to be revised speedily enough by ground methods, so the Ordnance Survey. people allocate areas to be photographed. Four hundred' square miles were done in 1935 and 490 square miles are to be; done this year. In addition, work is being carried out for ten borough and urban district councils independently. * EQUIPMENT USED. • Like most useful things, the process is comparatively simple. For ordnance map revision the machine flies on a series of parallel lines at 9000 ft and pictures are taken every few seconds, the exact period being based on the speeds of the wind and the aeroplane. A forward overlap - of about 60 per cent, is obtained, and the parallel lines are so arranged as to give 15 to 30 per cent, ovgrlap in the other dimension. The cantera, used automatically, attends to the winding of the film (which is 165 ft long and provides for 200 exposures 9in x 7in each), the setting of the shutter and the taking of the .photographs at predetermined intervals. A red light, and finally a green one, shows on the pilot's dashboard to warn him that the camera is about to expose, and he must then ensure, the machine is flying on a perfectly level-keel. ■ After the films are developed, contact prints are made to check whether there are any gaps in the overlap. The next process is to make a set of enlargements twice the linear dimension,; which brings the scale to thatiof the standard ordnance survey of l/'2sooth'. .These. are made on an enlarger, which has a tilting easel so that any slight deviation from :the absolute perpendicular of the camera can be corrected. INFINITE PAINS. The remainder of the process is mostly one of taking infinite pains. Each phonograph is carefully inspected, and the details seen are traced on to the existing maps. Even such ' small details as garden sheds are put in, so don't hope to get away with anything as large as a garage. Although, on the face of it, these surveys are expensive, most of them have proved profitable by reason of the increased rates obtained by the authorities—thus insult is added to injury. The aerial survey system is being employed in New Zealand also, not for the checking of garage and wash' house building by ratepayers in annual value areas, but tq complete the ordnance maps and for the preparation of special plans, maps, and reports. Aerial photography forms an important part in. Air Force activity in ail countries, and in New Zealand, where the equipment for other Air Force work is so limited, it forms an even larger proportion of total activities. .