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 ...

instrument for the evaluation of analog or digital

photogram A photogram is a 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 image th ...

s. It is based on the

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

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 The stereoautograph is a complex opto-mechanical measurement instrument for the evaluation of analog or digital photograms. It is based on the stereoscopy effect by using two aero photos or two photograms of the topography or of buildings from d ...

in 1907. The photograms or

photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...

s are oriented by measured

passpoint A hotspot is a physical location where people can obtain Internet access, typically using Wi-Fi technology, via a wireless local-area network (WLAN) using a router connected to an Internet service provider. Public hotspots may be created by ...

s 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, pro ...

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 Zeiss or Zeiß may refer to: People *Carl Zeiss (1816–1888), German optician and entrepreneur *Emil Zeiß (1833–1910), German Protestant minister and painter Companies *Carl Zeiss AG, German manufacturer of optics, industrial measurem ...

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