Patent GB-442854-A (GB)
Title: Improvements in and relating to methods and apparatus for measuring and reproducing bodies of all kinds by photographic surveying
IPC: G01C11/00
Filed: 1934-05-14
Abstract: 442,854. Photogrammetry. HORNER, E., 10, Am Karlsbad, Berlin. May 14, 1934, No. 4900. [Classes 97 (i), 97 (ii), and 98 (ii)] For producing maps &c. of three dimensional bodies and particularly of the surface of the earth from stereoscopic photographs two or more projection chambers 40, Fig. 2, containing the stereoscopic photographs are fixed relatively to a drawing and measuring table 5 in positions corresponding to those when the photographs were taken, an optical model of the object photographed being formed without the interposition of ray reflecting means by the intersection of corresponding rays above the table and being explored by a mapping device 4 displaceable over the table and furnished with an index plate 3 on which the corresponding rays intersect. The magnification of the projections is about 6À2 to 8. Small bright sources of light 6 are used for projection and are connected to the mapping device 4 by links 7, 8, pivoting about the objectives of the projection chambers so that the main rays are directed on to the index plate 3, which is vertically adjustable on the device 4. Fig. 4 shows a projection chamber with means for effecting internal orientation of the photographic plates. Aiming devices 10, 11, 12, fixed on the objective support 9 are directed towards fixed marks 13, 14, 15 on the plate carrier 16 by tilting the carrier 9 by means of screws 17, 18, 19. The carrier 9 is adjustable in a dovetail groove 22. A fixed reflector 21 at the mark 14 and a scale 20 enable the aiming device 11 to be used for determining the distance of the objective from the plate. The external orientation is effected by using a mark on the plate indicating the plumb point (i.e. the point at which the plumb line through the objective met the plate during exposure). If the plumb points are not marked on the plates, the projectors are adjusted in their supporting frame 26 by trial and error to produce an optical model in the space between the projectors and the table 5. Points lying in the same plane are fixed in the optical model by pointers 30, 31, 32 adjustably mounted in the frame 26. The table 5 which is formed as the diametral plane of a universally adjustable hemisphere 27 carried by telescoping supports 28 operated by an endless band 29, is moved so as to contact with the three pointers 30, 31, 32. The accuracy of the adjustment may be increased by providing. the pointers 30, 31, 32 with mechanical, electrical, visual, or acoustic signalling devices for indicating the contact pressure. An aiming device 36 on the part 4 at right angles to the table 5 enables the plumb points to be located on the plates. Luminous marks 37 are universally suspended vertically below the front principal points of the objectives to assist this operation. The table 5 is then restored to the horizontal and the external orientation of the projection chambers effected by means of aiming device 36 and the marked plumb points on the plates. In order to increase accuracy in the determination of the ray intersections the mark on the index plate 3 may be replaced either by a diffraction grating or a reflecting cone in which case the rays unless they intersect precisely at the apex of the cone will be reflected from its conical surface to a surrounding spherical bowl where their separation will be clearly visible. The device 4 carries a pricker or pencil vertically below the mark on the index plate 3. For control purposes the photographs may be stereoscopically observed simultaneously with the determination of the ray intersections. Semi-transparent reflectors 38, Fig. 2, are provided in the direct path of the rays from the projectors so that projected images may be cast via the reflectors 41 on to lateral image planes 39 carried by the table 5. Alternatively twin projection chambers coupled to the main projection chambers may be used for projection on to the planes 39. The stereoscopic picture may be viewed in the oculars 42 which are provided with observation tubes 43 extending underneath the planes 39. Stereoscopic marks adapted to appear in the images on planes 39 at a point corresponding to that determined by the intersection of rays on the index plate 3 are projected on to planes 39 by lamps 47a carried by the device 4 and geared so that their separation increases or decreases as the index plate 3 is raised or lowered. Various modifications for viewing auxiliary projections of the photographs for control purposes either stereoscopically or pseudostereoscopically are described. Mouldable material may be made to coincide with the optical model. The relief model thus obtained may be coated, e.g. by spraying, with a lightsensitive layer, placed in coincidence with the optical model and the latter photographically recorded. Before development the contour lines &c. may be recorded photographically by projecting on to the relief model a photograph of a previously prepared map. Specifications 182,912, [Class 97 (ii)], 342,683, and 355,443 are referred to.