Improvements in aircraft cameras for taking photographs for radial nadir point triangulation

摘要

669,959. Cameras for aerial surveying. NISTRI, U. Nov. 8, 1949 [Feb. 1, 1949], No. 28639/49. Class 98 (i). A camera for taking aerial photographs of the ground about a substantially vertical axis to effect radial nadir point triangulation is characterized by means whereby the indication of the position of the nadir point on the photograph of the ground is obtained on the photograph itself in the form of a reference which is capable of being clearly associated with a topographical detail of the ground which coincides with the nadir point, or with the intersection of the principal optical axis of the camera lens with the plane of the photographic plate, this indication being obtained by means of a projector consisting of a lens and illuminated grid or like indicator, the image of said grid or the like being projected by reflectors through the camera lens on to the same plane as the image of the ground at the same instant as the photograph is taken. As shown, an image at infinity of a grid 5 projected by a lens 4SP1/SP and mirrors 6, 7 is recorded on a photographic material in the focal plane 10 of an aeronautical camera by the objective 8 which photographs the terrain,. the mirror 7 being controlled by a gyroscope 19, the axis 17 of which may be held truly vertical by. known means employing a pendulum erector device so that the beam from the mirror 6, which beam is parallel to the constrained axis 12 of the gyroscope, is reflected in the true vertical direction.