Patent GB-445716-A (GB)
Title: Improvements in or relating to plotting maps
IPC: G01C11/00
Filed: 1934-10-23
Abstract: 445,716. Photogrammetric apparatus. TENNANT, W. J., 111, Hatton Garden, London.-(Miller, O. M. ; 156th Street, Broadway, New York, U.S.A.) Oct. 23, 1934, No. 30415. [Class 97 (i)] Stereogrammetric apparatus for plotting contour lines from a pair of overlapping photographs obtained from the ends of an aerial base, comprises adjustably - mounted supports for the photographs and optical observing- devices associated with the supports, the rays from the photographs being directed into the observing-devices by mirrors each having a small aperture through which an index mark is observed. The two mark images combine in the eyepieces to form a single stereoscopic image, the apparent height of which can be adjusted by displacing the mark carriers. The mark image can then be displaced over the image of the photographs at a constant apparent height to enable contour lines to be traced. The apparatus shown comprises a support 15, in the form of an open framework, on which is mounted a rectangular frame 38 supporting the carriers 10, 37, for the photographs, and the observing devices 13, 45. The frame 38 is mounted on the support 15 by legs 39, 40, 41, provided at their lower ends with wheels 42 resting on rails 43 to enable the frame to be turned in azimuth. The legs 40, 41 are pivoted at 80, 79 to the rear and front members 78, 77 of the frame and the leg 39 is slidably mounted in a block 81 to enable the frame to be tilted about the axis 79, 80. The eyepieces 13, 45 are secured to brackets 54, 55, secured to a transverse member 56 of the frame 38. A transverse member 57 having its ends 58, 59 pivotally mounted in the side members 51, 52 of the frame carries a bracket 61 which is attached to it by a pivot 62, the upper end of the bracket being formed as a circular guide 63 in which rests a bar 64 secured to the carrier 37. The " left-eye " photograph is mounted in the rear end of the carrier 37 which has at its front end a collimating lens, the axis of which passes through the centre of the guide 63. The rays from this lens are directed into the left-hand observing device by a mirror 46 which is rigid with the observing-means These means comprise, in addition to the eyepiece 45, a system of lenses and mirrors giving a wide field of view so that the whole of the photograph can be observed. The mirror 46 has a small central aperture 47 through which is seen a mark carried by an internally-illuminated tube 48. The support for the picture-carrier 10 comprises a cranked member 19 mounted on pivots 20, 21, coaxial with the pivots 79, 80, in fixed standards 22, 23. Pivoted at 27 to the member 19 is a bracket 24 provided at its upper end with pivots 30, 31 for arms 32, 33 supporting the carrier 10. The mirror 16 associated with the carrier 10 is rigidly carried by a bracket 14 secured to the support 15 in such a position that the axis 79, 80 passes through the aperture 17 of the mirror. A mark carried by an internally-illuminated tube 18 is observed through the aperture 17. The tubes 18, 48 are mounted in a carrier 49, the tube 18 being fixed in the carrier and the tube 48 being displaceable along a rod 86 by a screw 83. A bracket 99 secured to the carrier 49 is provided with stubs 97, 98 engaging a sleeve 96 slidably mounted on a rod 53. The carrier 49 is slidably mounted on a rod 88, the downturned ends 90, 91 of which are slidably mounted in sleeves 92, 93 connected by pivots 94, 95 to the frame 38. The upper end of the rod 53 is secured to a carriage 100 carrying a marker 11 by which the contour lines are traced on a surface A mounted on the upper part 12 of the support 15. The carriage 100 is slidably mounted on a bar 101 provided at its ends with sleeves 102 which are slidably mounted on rods 103 carried by the support. It is assumed that on each photograph the optical centre is known, and that the photograph includes images of at least three ground points which have been located by triangulation. The carriers 10, 37 are angularly adjusted with the aid of these known datum points, the method of adjustment being fully described in the Specification. On looking through the eyepieces the observer sees the stereoscopic mark image superposed on the stereoscopic image of the photographs, and by displacing the carriage 100 a number of points can be obtained at which the mark image touches the landscape image. These points are all in the same horizontal plane so that the marker 11 in moving through them traces a contour line. Lines at various heights can be obtained by vertically adjusting the carrier 49.