Patent GB-352459-A (GB)
Title: Improvements in or relating to the optical projection of the recorded images of photographically recording theodolites
IPC: G01C11/28
Filed: 1930-04-07
Abstract: 352,459. Photographically recording theodolites. ASKANIAWERKE AKT.- GES. VORM. CENTRALWERKSTATT DESSAU UND C. BAMBERGFRIEDENAU, 87, Kaiserallee, Friedenau, Berlin. April 7, 1930, No. 11065. Convention date, April 6, 1929. [Class 97 (ii).] The recorded images of photographically recording theodolites are optically projected and a measuring scale adjusted in accordance with the registered angle of elevation is superposed on or included in the projected image so that the corrections to be applied to the registered angles when the object does not coincide with the zero point of the fixed co-ordinate system in the theodolite may be read directly. In one form the measuring scale may be included in the recorded image by using a theodolite having in front of the film a rectangular grid which is automatically rotated so that its plane makes an angle with the plane of the film equal to the angle of altitude of the theodolite. Alternatively the rectangular grid may remain in a plane parallel to the film and be rotated about the axis of the theodolite through an angle equal to the angle of elevation of the theodolite ho, giving rise to a recorded image as shown in Fig. 6. When the recorded images are projected the corrections x sec ho and y to be applied to the registered angles of azimuth ao and altitude ho of the theodolite respectively, where x and y are the co-ordinates of the object relative to the zero point of the fixed co-ordinate system of the theodolite, may be read directly. Fig. 7 shows a modification in which the measuring scale is manually superposed on the projected image which is arranged on the ground glass plate 6. The measuring scale comprises a graduated rule 9 pivoted to a slide 9a and having an extension 9c lying over an angle indicator 11. The slide 9a is movable on the bar 8 which in turn may move parallel to itself along the bar 7 so that the rule 9 may be adjusted to pass through the image F of the object and make an angle ho to the x axis of the fixed co-ordinate system, the correction to the azimuth angle a being read off by the length of rule 9 intercepted between the y axis and the point F. Alternatively the rule 9 may be optically projected on the screen 6. In a further modification, Fig. 9, the photographic record is projected into the field of view of an eyepiece 17 on the upper side of a casing 13. Below the eyepiece 17 is a frame 20 which may be moved in the direction of the x axis of the image by the handle 21 having a toothed sector 22 engaging a rack 23. The frame 20 carries a glass plate having a scale 24, Fig. 11, parallel to the y axis and a further glass plate having a scale 29 and rotatable in the frame 20 by means of the handle 26 so that the zero points of the two scales always coincide. The corrections to be applied to the azimuth ao and altitude ho angles are given by FoF1 and F1x, Fig. 11. The measuring scales used are suitably chosen in accordance with the focal lengths of the objective of the recording theodolite and the projection system.