National Geographic : 1914 Jun
MAP-MAKING FROM PHOTOGRAPHS This photograph was taken by a camera specially designed for photo-topographic work (see page 669). The rear frame ofthe inner camera box is supplied with notches to mark the horizon and the principal lines. All these notches print on theedges of the negatives, giving ready means for checking distortions in the prints, and at the same time showing the scale in conjunction with thecross-lines. Inthis picture, reading from left to right, two triangulation stations are shown, then a camera point (marked No. 4), then the height(in meters) offour peaks, etc. From such photographs it is possible to construct an accurate map of the region within the field of vision.