Effect of Enlargement of a Photographic Image on Some Measuring Properties of Aerial Photographs

摘要

An aerial photograph enlarged to the scale 1:M, and obtained from an aerial negative taken from a great height, in many respects has better measuring properties than does a contact print from an aerial negative taken directly in the scale 1:M from a lower height. It is more feasible for the contour and composite surveys to conduct the photographing from as great a height as possible, taking into account the maximum enlargement ratio at which a satisfactory photographic quality of the aerial negatives is obtained. It is possible to conduct aerial photographing to large and medium scales of surveying, figuring on a subsequent magnification of the aerial photographs by 4 - 8 times. In addition, in many cases, the various establishments can successfully utilize the already available aerial negatives from prior surveys with an enlargement of the photo-image by 3 - 4 times, and sometimes even more. The enlargement ratios will increase in value in proportion to the development of science and technology. The use in production of high enlargement ratios for a photo-image will permit us to raise appreciably the output and economy of the aerial photogeodetic operations in contour and composite surveying without a decrease in the accuracy of the maps and charts.