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Common points are identified on each image. A line of sight (or ray) can be constructed from the camera location to the point on the object. It is the intersection of these rays ( Triangulation ) that determines the three-dimensional location of the point. More sophisticated Algorithm s can exploit other information about the scene that is known '' A Priori '', for example Symmetries , in some cases allowing reconstructions of 3D coordinates from only one camera position. Photogrammetry is used in different fields, such as Topographic Map ping, Architecture , Engineering , Police investigation, and Geology , as well as by Archaeologists to quickly produce plans of large or complex sites. It is also used to combine Live Action with Computer Generated Imagery in movie Post-production ; '' Fight Club '' is an excellent example of the use of photogrammetry in film. Algorithms for photogrammetry typically express the problem as that of minimizing the sum of the squares of a set of errors. The minimization is itself often performed using the Levenberg-Marquardt Algorithm . PHOTOGRAMMETRIC METHODS ''Photogrammetry'' is a collection of methods for several Geodetic tasks. The data model on the right shows what type of information can go into and come out of photogrammetric methods. The ''3D co-ordinates'' define the locations of object points in the 3D space. The ''image co-ordinates'' define the locations of the object points' images on the film or an electronic imaging device. The ''exterior orientation'' of a camera defines it's location in space and it's view direction. The ''inner orientation'' defines the geometric parameters of the imaging process. This is primarily the focal length of the lens, but can also include the description of lens distortions. Further ''additional observations'' play an important role: With ''scale bars'', basically a known distance of two points in space, or known ''fix points'', the connection to the basic measuring units is created. Each of the four main variables can be an ''input'' or a ''result'' of a photogrammetric method. EXTERNAL LINKS
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