The stereoautograph is a complex opto-mechanical

measurement Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to ...

instrument for the evaluation of analog or digital

photogram A photogram is a Photography, photographic image made without a camera by placing objects directly onto the surface of a light-sensitive material such as photographic paper and then exposing it to light. The usual result is a negative shadow im ...

s. It is based on the

stereoscopy Stereoscopy, also called stereoscopics or stereo imaging, is a technique for creating or enhancing the depth perception, illusion of depth in an image by means of stereopsis for binocular vision. The word ''stereoscopy'' derives . Any ster ...

effect by using two aero photos or two photograms of the topography or of buildings from different standpoints. It was invented by Eduard von Orel in 1907. The photograms or

photographic plate Photographic plates preceded film as the primary medium for capturing images in photography. These plates, made of metal or glass and coated with a light-sensitive emulsion, were integral to early photographic processes such as heliography, d ...

s are oriented by measured passpoints in the field or on the building. This procedure can be carried out digitally (by methods of triangulation and

projective geometry In mathematics, projective geometry is the study of geometric properties that are invariant with respect to projective transformations. This means that, compared to elementary Euclidean geometry, projective geometry has a different setting (''p ...

or iteratively (repeated angle corrections by congruent rays). The accuracy of modern autographs is about 0.001 mm. Well known are the instruments of the companies

Wild Heerbrugg The Wild (Heerbrugg) company (pronounced "vilt") was founded in 1921 in Switzerland. The company manufactured optical instruments, such as surveying instruments, microscopes and instruments for photogrammetry among others. The company chang ...

(Leica), e.g. analog A7, B8 of the 1980s and the digital autographs beginning in the 1990s, or special instruments of Zeiss and Contraves.

References

*Gilbert Willy *Military Topography and Photography by Floyd D. Carlock, U.S. Army, 1916, p.104 ff, with photos (Available online at Google Books) {{Stereoscopy Measuring instruments Photogrammetry Optical instruments Cartography Stereoscopic photography