Patent GB-196916-A (GB)
Title: Improvements in apparatus for automatically drawing maps and plans from two terrestrial or aerial photographs
IPC: G01C11/00
Filed: 1923-04-20
Abstract: 196,916. Poivilliers, G. J. April 25, 1922, [Convention date]. Stereogrammetric apparatus for producing contour maps from oblique terrestrial or aerial photographs of the kind in which the photographs are observed through similar objectives to those used in the cameras by means of a fixed binocular telescope, is arranged so that the line of sight of the telescope L is always in a vertical plane, the chambers A containing the photographs being tilted about a horizontal axis e, e for setting to a particular contour and rotated about a vertical axis for drawing the contour. The movements of the photographs and of the outer ends of the telescope in a vertical plane are effected by control mechanism composed of straight guides and fixed centres. Two straight guides R1 mounted on axes I, and engaging rollers g<1> on slides C1 adapted to travel along bars P, carry the chambers A. Both bars P are parallel to the line I1, I1 and are supported in the slide dg, but one bar is nearer to the line I1, I, by an amount C1 corresponding to the difference in depth position of the objectives S, S1, Fig. 1, when taking the photographs. The outer ends of the bars P are carried by slides G<1> and the slides C, are connected by a rigid rod, adjustable in length. Movement of the slides C1 is effected by the hand-wheel M<1> through the shaft a<1> and a screwed spindle carried by one of the bars P. The angles between the guides R, and the line I1I1 are always equal to a, a<1>, Fig. 1. The slide C1 and the bars Pare operated by the spindle V and carry a marker m attached to one of the carriages C1 for drawing the contours &c. on the board U. As the telescope L is always sighted in a vertical plane, the angle of inclination i, Fig. 1, of the line of sight with the vertical is varied by tilting the outer ends l of the telescope L by mechanism operated from a second pair of slides c2 on the bars P. These slides C2 are connected by a rod t2 of variable length and carry rollers g2 which rotate guides R2 about axes I2 on the line I1I1. The slides C2 are set so that the distances of the rollers g2 from perpendiculars to the line I2I2 are equal to the heights of the points S, S<1> less the distance h, Fig. 1, and the guides R2 thus make angles #, #<1> with the line I1, I1. Slides C2 are adjusted by a foot-wheel M2 and a spindle V2. To each of the guides R2 is fixed a guide r2 at right angles thereto which moves a roller g3 on a slide C3 carried by a guide b, connected as shown, by links r1 to the guides R1. A guide r3 carried by the slide C3 is provided with a roller g4 engaging a lever r4 fixed on the movable outer end of the telescope. The line of sight of the telescope is thus maintained at the appropriate angle i, Fig. 1. The telescope, Fig. 5, comprises objectives o1 behind optical squares p1 carried by the movable portions l1l2, together with pointers f situated in the focal plane. Reflectors p2p3 reflect the rays into the fixed portion of the telescope which contains prisms W adjusted to erect the images in the eyepieces o4. Contours are drawn by operating the wheels M, M1, M2 so that the pointer f is maintained in contact with the image of the ground at the desired height. Lines of gradient can be drawn in a similar manner by turning the photographs through a right angle and erecting the image in the eyepieces by the prisms W. In one modification the chambers are rotated about horizontal axes and the outer ends of the telescopes aronud vertical axes. In another modification the chambers are fixed and the movable portions of the telescope are arranged to control the rotation of the crrecting prisms W. The contours &c. may be recorded on a drum u<1>, Fig. 7, the marker m being carried bv a slide P2 and actuated from the slide C2 through the lever R4, as shown. The scale may be altered by drawing the contours through the medium of an enlarging or reducing pantagraph. In a further modification the chambers remain stationary during the observation, and the outer ends of the telescope are fitted with collimators rotated through the appropriate angles by mechanism similar to that in the previous arrangements.