677,786. Stereophotogramometric apparatus. SANTONI, E. Aug. 10, 1949 [Aug. 28, 1948], No. 20848/49. Class 97 (i). In apparatus of the type described in Specification 306,965, [Class 97 (i)], comprising two photogram-bearing frames moved for plotting in two perpendicular directions by two guide rods universally pivoted thereto, the observing system is located beneath the photograms and comprises two systems each consisting of a tube carrying an objective forming an image of a portion of the photogram on a mark carried thereby, light for which is reflected by a mirror to a collimating lens, passes an Amici erecting prism and a second lens and is reflected by a second reflector to an eyepiece, each reflector being arranged to rotate through an angle equal to half that through which the optical axes on either side thereof rotates to maintain the image in the field of view. As shown diagrammatically in Fig. 1 the photographs fs, fd are each supported on a plate 9 movable in two perpendicular directions on a plate 7 supported on an axle 6<SP>11</SP> for rotation about an axis #. The axle is in turn supported on an axle 6 rotatable about an axis # in a support bz vertically movable on a column 5 fixed to a slide by sliding on a slide bx which can slide in a perpendicular direction on a column 2 fixed to the base 1. The photographs are observed through oculars Os, Od and optical systems comprising an objective 01 and a reference mark m in a tube 8 on the plate 6, a mirror S1, lenses 02, 03 between which the rays are collimated and pass through an Amici prism A and a mirror S2. The photographs are moved relative to the viewing systems by rods 11, 13 connected by a joint 14 to the plotting table 15 movable as is usual along guides X, Y and Z. The rods are pivoted on universal joints 10 at the intersection of axis # and # and extend into rods 11<SP>1</SP> engaging on extensions 12 of the plates 2. Thus in operation the plates 9 are tilted about the axes #, # by suitable worm gearing to correspond to the tilt of the camera in taking, the tubes 8 bearing part of the optical system being similarly tilted. The rods 11, 13 then move the photographs to allow successive portions to be viewed together with the marks m to permit plotting. In the embodiment shown in plan in Fig. 3 and side elevation in Fig. 2 the photograph fs is rotatably mounted on a plate 24 movable in guides 231, 23<SP>11</SP> on a frame 23 movable along perpendicular guides 21<SP>1</SP>, 21<SP>11</SP> in a frame 21 rotatably supported by a fork 18<SP>1</SP> so as to be tilled about axis #. The fork 18<SP>1</SP> is on a shaft 18 rotatable about the axis # by a worm and gear 20, 19. The plate 24 is moved by means of an extension 24<SP>1</SP> thereof engaged by a pin 26, Fig. 2, sliding in a tube 27 forming one of the rods 11, 13 and supported by a universal joint 28, the distance between the front and the end of the rod being adjustable to the focal length of the camera used in taking. The objective 01 and mark m are in a tube 31 fixed to the shaft 18 and pivotally carrying the mirror S1 and objective 02 in a tube 32 sliding in a tube 38 bearing the prism A. The objective 03, mirror S2 and ocular Os are similarly held in pivoted tubes 33, 34. A gear or linkage system is provided to rotate the mirrors S1, S2 to maintain the image in view as the tubes 33, 34 and 31, 32 rotate relative to each other.