Photogrammetry (from photo ... , other Greek. Γράμμα - recording, image and ... metry ) is a scientific and technical discipline involved in determining the shape, size, position and other characteristics of objects from their photo images [1] .
There are two main directions in photogrammetry: creating maps and plans of the Earth (and other space objects) from photographs (phototopography), and solving applied problems in architecture , construction , medicine [2] , forensics , etc. (ground-based, applied photogrammetry) [3] .
Photogrammetry appeared in the middle of the XIX century , almost simultaneously with the appearance of photography itself. The use of photographs to create topographic maps was first proposed by the French surveyor Dominic F. Arago around 1840.
Scopes of photogrammetry
Photogrammetry is used in various activities:
- creation of topographic maps and GIS ;
- geological surveys;
- environmental protection (study of glaciers and snow cover, soil assessment and study of erosion processes, observation of changes in vegetation cover, study of sea currents);
- design and construction of buildings and structures;
- archaeological site [4] ;
- film industry (combining the game of live actors with computer animation , for example, in the films “ Fight Club ” , " Avatar ", etc.).
- automated construction of spatial models of an object from images
- in military affairs: to create topographic and special maps, photo documents, to consolidate geodetic reference networks, to determine the coordinates of targets and their troops, to study the trajectories and flight speeds of shells and missiles, etc. [5]
- computer games (creating three-dimensional models of game objects, creating realistic terrain, examples of use: Resident Evil 7: Biohazard , World of Tanks).
General principles of photogrammetry
Photogrammetry uses methods and techniques of various disciplines, mainly borrowed from optics and projective geometry .
In the simplest case, the spatial coordinates of the points of an object are determined by measurements taken from two or more photographs taken from different positions. In this case, common points are found on each image. Then a line of sight is drawn from the location of the camera to a point on the subject. The intersection of these rays determines the location of the point in space. More complex algorithms can use other, known in advance, information about the object: for example, the symmetry of its constituent elements, which in certain cases allows reconstructing the spatial coordinates of points using only one photographic image.
The algorithms used in photogrammetry are aimed at minimizing the sum of squares of the set of errors, usually solved using the Levenberg-Marquardt algorithm (or the bundle method ), based on the solution of non-linear equations by the least squares method .
The diagram shows four main types of data that can be both input and output in the production of photogrammetric work:
- spatial coordinates determine the position of the points of the object in space;
- the coordinates in the photo determine the position of the points of the object in an analog or digital image;
- external orientation elements of the camera determine its position in space and the direction of shooting;
- interior orientation elements determine the geometric characteristics of the shooting process.
Elements of exterior orientation include the three-dimensional coordinates of the center of the projection, the longitudinal and transverse angles of inclination of the image, and the angle of rotation. Elements of interior orientation include, first of all, the focal length of the lens (although the nature of the distortions introduced during shooting can be taken into account: for example, lens distortion , deformation of photographic material, etc.) and two-dimensional coordinates of the main point.
Additional observations help to more accurately determine the distances and coordinates of the points of the object, as well as to specify the scale and the coordinate system itself.
Advantages of Photogrammetry
- High accuracy of measurements;
- A high degree of automation of the measurement process and the related objectivity of their results;
- Great performance (since the objects themselves are not measured as such, but only their images);
- Possibility of remote measurements in conditions when staying at the facility is unsafe for humans.
See also
- Digital Photogrammetric Station
- Aerial photography
- Stereoscopy
- Triangulation
- Orthophotomap
- Digital elevation model
- PHOTOMOD
Notes
- ↑ Photokinotechnics, 1981 , p. 358.
- ↑ S. Mirov, A. Ivanov, T. Ogurtsova, E. Dyukendzhiev. Application of remote sensing data in the submetry // 4th International Conference of Users of DSP PHOTOMOD: Collection of Abstracts. - 2004 .-- S. 25-28 .
- ↑ Mikhailov A.P., Chibunichev A.G. Lecture course on photogrammetry of MIIGAiK . Racurs (March 26, 2013).
- ↑ L.V. Bykov, A.L. Bykov, M.V. Lashov, L.V. Tataurova. Geodetic support of archaeological research . Bulletin of Omsk University. No. 3 (65), 2012 - S. 85-93.
- ↑ Photogrammetry // Military Encyclopedia / P. Grachev . - Moscow: Military Publishing House, 2004. - T. 8. - S. 281.
Literature
- Aleksapolsky N. M. Photogrammetry: Part 1 / Under the general. ed. doctors tech. sciences prof. A. N. Lobanova. - M .: Geodesizdat , 1956 .-- 412 p. - 3,600 copies.
- E.A. Iophis . Photokinotechnics. - M .: "Soviet Encyclopedia", 1981. - S. 358. - 449 p. - 100,000 copies.
- A.N. Lobanov. Photogrammetry / N. T. Kuprina, 3. N. Chumachenko. - M .: "Nedra", 1984. - 552 p. - 7 900 copies.