Patent GB-1056784-A (GB)
Abstract: 1,056,784. Photo-grammetry. SOC. D'OPTIQUE ET DE MECANIQUE DE HAUTE PRECISION. March 26, 1964 [March 26, 1963; June 26, 1963], No.12928/64. Heading G1F. A photo-grammetric plotting machine comprises two rods 5, 6 (one of which and its associated mechanism is shown in Fig. 1), which represent in effect lines drawn from homologous points on a pair of stereophotographs the two rods being articulated at a point 4 which is representative of the ground point under consideration, the two rods also being mounted in universal joint devices provided with transducers for providing electric signals representative of the inclinations of the two rods, and a stereo-comparator provided with carriages for the two photographs, binocular viewing means, and further transducers connected to the first transducers for correlating the movements of the carriages and electrical signals representative thereof with the inclinations of the rods. The point 4 can move vertically on a carriage 3 and horizontally on carriages 2, 1. Each rod is slidably mounted in a sleeve 7 articulated on a fork 8 about an axis 9. The fork 8 is pivotally mounted in a cradle 13 about an axis 10 and operates an angle detector 19. Each rod also engages a slotted member 12 pivotally mounted about an axis 11 perpendicular to the axis 10. Movement of the member 12 about the axis 11 operates an angle detector 22. The cradle 13 is carried by a cradle 14 pivotable about an axis 16. By movement of the cradles, 13, 14 the plane containing the axes 10, 11 may be set to compensate for any inclination of the photograph when taken. The angle c which the point force obtends at the junction of the axes 10, 11 relative to the vertical can be split into two angles a, b which are projections of the angle c on to the vertical plane containing the axes 11, 10 respectively. These angles a, b are sensed by the detectors 19, 22. Fig. 3 shows a mounting for one of the photographs 24, the other is mounted similarly. The photograph 24 is mounted in a carriage 25 in a way which allows for tilt, the carriage being movable on a bar 28 by use of a motor 29 and drive-screw 30. The bar 28 is mounted on a carriage 26 movable along a fixed bar 33 by use of a motor 34 and drive-screw 35. Carriage 25 has a yoke 40 mounted in a pivot 39 and in which slides a bar 37. Movement of the carriage 25 along the bar 28 pivots the bar 37 to rotate a vertical spindle 38 which drives an angle detector 45. The spindle 38 and angle detector 45 are mounted on a carriage 46 adjustable by a knob 50 to make the distance between the spindle 38 and a line through the pivot 39 parallel to the bar 28 equal to the focal length of the camera lens, f, used in taking the photograph 24. When the angle detector 45 registers the same angle as the detector 22, the photograph 24 as seen in the binocular eye-piece through which it is viewed, is positioned in correspondence with the positioning of the point 4, in the direction given by the bar 28 on the one hand and the axis 10 on the other. A similar bar 61 and angle detector 55 is provided for positioning the photograph 24 in correspondence with the point 4 as far as the directions at right angles to those above are concerned. The angle detectors 19, 22 are coupled to the motors 29, 34 and the angle detectors 45, 55 to cut off the motors 29, 34 when the detected angles are the same for each corresponding pair of detectors. A modified form of apparatus is described wherein the motors 29, 34 are replaced by hand-wheel drive, which also drives the carriages 1, 2, 3 for the point 4, and in which electric motors are provided to effect small correcting movements of the photographs only.