THE USD-1 DROBYSHEV UNIVERSAL STEREOGRAPH,
ARMY ENGINEER RESEARCH AND DEVELOPMENT LABS FORT BELVOIR VA
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The USD-1 provides exact fixes for aerial photographs with angles of inclination up to 3 degrees, because the centers of rotation of the correction planes pass through the point of zero distortion on the photograph and also because special correction plates are used. These latter provide correction of the azimuthal distortion arising from the horizontal position of the photograph in the instrument. The detailed theory of the universal stereograph is to be found in Drobyshevs book Principles of Aerial Photography and Photogrammetry. Moscow, Gosgeoltekhizdat, 1963. The USD-1 can handle photographs corresponding to f of 55 to 200 mm the angles alpha and omega can range up to 2 degrees for f 55 mm and 3 degrees for f 55 mm. The scale of the model produced in the instrument is 1.3 times that of the photographs. The focal length F is 140 mm.