GB317216A - Apparatus for plotting maps from air photographs - Google Patents

Abstract

317,216. Barr & Stroud, Ltd., and Barr, A. Aug. 1, 1928. Photographic surveying-instruments. - Apparatus of the epidiascope kind for plotting on a map surface details of the area represented on an aerial photograph when the map positions of three or more control points which can be identified on the photograph are known, comprises a photograph holder A, a map holder B, and between them a lens system C, all mounted on a base D. The photograph holder comprises a board 1 to receive a paper print which is illuminated by lamps 5. The holder can be adjusted about a vertical axis 2, preferably by Bowden wires 3. The map holder comprises a frame 6 carrying a transparent plate 7 over which is placed a sheet of tracing paper &c. so that the image of the photograph formed on the back of the paper can be seen from the front to enable details to be traced in. The frame 6 is adjustable about a horizontal axis 8 by screws 9 and may also be arranged to be rotatable in its own plane. The lens system is mounted so as to be adjustable about a horizontal axis 14 and a vertical axis 16 in a frame 12 which is vertically adjustable in a standard 10, the latter being adjustable in a transverse direction in a block 11. Both the board 1 and the block 11 are adjustable to and fro along the baseboard D to enable the scale of the projected image of the photograph to be brought into agreement with that of the map. The parts are adjusted until the projected images of the three control points on the photograph coincide with the same three points as shown on the map. The lens system can then be separately adjusted to obtain the best definition over the area to be mapped. A diapositive illuminated from the back may be used for projection instead of the paper print.,