Photogrammetry

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Photogrammetry is the science that makes measurements of photographs, especially to restore the position of the right surface point. Photogrammetry is as old as modern photography, dating to the mid-19th century and in the simplest example, the distance between two points located on the plane parallel to the photographic image plane can be determined by measuring their distance to the image, if the scale (s ) of the unknown image.

Photogrammetric analysis can be applied to a single photograph, or may use high-speed photography and remote sensing to detect, measure and record complex 2-D and 3-D motion fields by providing image measurement and analysis to the computational model in an attempt to estimate sequentially -raw. , with an increase in accuracy, the actual 3-D relative movement.

From its beginnings with stereoplotters used to plot contour lines on topographic maps, it now has a very wide use.

(See also sonar, radar, lidar, etc.).

Video Photogrammetry

Metode fotogrametri

Photogrammetry has been defined by the American Society for Photogrammetry and Remote Sensing (ASPRS) as an art, science and technology to obtain reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic and photographic patterns of luminous electromagnetic recordings. energy and other phenomena.

Photogrammetry uses methods from many disciplines, including optics and projective geometry. Digital image capture and photogrammetry processing include several well-defined stages, allowing to produce 2D or 3D digital models of the object as end products. The data model on the right shows what kind of information can enter and exit the photogrammetry method.

Coordinate 3-D determines the location of object points in 3-D space. The coordinate image determines the location of the image points object on the film or electronic imaging device. The camera's exterior orientation defines its location in the space and direction of its view. Orientation in defines the geometric parameters of the imaging process. This is primarily the focal length of the lens, but may also include a description of lens distortion. Further additional observations play an important role: With the scale bar , basically the known distance from two points in space, otherwise known repair point , the connection to the base measuring unit is made.

Each of the four main variables can be either input or output of the photogrammetric method.

The algorithm for photogrammetry typically tries to minimize the sum of the squares of errors over the coordinates and relative displacements of the reference points. This minimization is known as bundle adjustment and is often done using the Levenberg-Marquardt algorithm.

Stereophotogrammetry

A special case, called stereophotogrammetry , involves estimating the three-dimensional coordinates of a point on an object using measurements made in two or more photographic images taken from different positions (see stereoscopy). Common points are identified on each image. The line of sight (or rays) can be constructed from the camera location to the point on the object. This is the junction of these rays (triangulations) that determine the three-dimensional location of the point. More sophisticated algorithms can exploit other information about known scenes a priori , such as symmetry, in some cases allowing 3-D coordinate reconstruction from only one camera position. Stereophotogrammetry emerged as a powerful non-contact measurement technique for determining the dynamic characteristics and form of non-rotating and rotating structural mode.

Maps Photogrammetry

Integration

Photogrammetry data with solid range data where scanners complement each other. Photogrammetry is more accurate in x and y directions while range data is generally more accurate in the z direction. This range data can be provided with techniques such as LiDAR, laser scanners (using flight time, triangulation or interferometry), white-light digitizers and any other technique that scans the area and returns x, y, z coordinates for some discrete points (commonly called " cloud point "). Photographs can clearly determine the edges of buildings when cloud tracks can not. It is useful to combine the advantages of both systems and integrate them into creating better products.

3-D visualizations can be created with georeference of aerial photography and LiDAR data in the same reference frame, orthorectifying aerial photographs, and then draping an orthor- gic image over a LiDAR grid. It is also possible to create digital terrain models and 3-D visualizations using pairs (or multiples) of aerial or satellite images (eg SPOT satellite imagery). Techniques such as adaptive least squares stereo matching are then used to generate solid correspondence arrays that are modified through the camera model to generate a solid array of x, y, z data that can be used to generate digital terrain models and orthoimage products. Systems using this technique, e.g. ITG systems, developed in the 1980s and 1990s but have since been replaced by LiDAR and radar-based approaches, although this technique may still be useful in deriving elevation models from old aerial photographs or satellite imagery.

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Apps

Photogrammetry is used in areas such as topographic mapping, architecture, engineering, manufacturing, quality control, police investigation, and geology. Archaeologists use it to quickly produce large or complex site plans, and meteorologists use them to determine the speed of a tornado wind when objective weather data can not be obtained.

It is also used to combine direct action with computer-generated imagery in post-production films; Matrix is a great example of using photogrammetry in movies (details are provided on extra DVDs). Photogrammetry is widely used to create photorealistic environmental assets for video games including The Vanishing of Ethan Carter and EA DICE Star Wars Battlefront. The main character of the Hellblade game: The Sacrifice of Senua comes from a photogrammetric motion capture model taken from actress Melina Juergens.

A somewhat similar app is object scanning to automatically create its 3D model. Some programs like 3DF Zephyr, RealityCapture, Acute3D's Smart3DCapture, are now part of Bentley Systems and renamed ContextCapture, Pix4Dmapper, Photoscan, 123D Catch, Bundler, PIXDIM and Photosketch toolkits have been created to allow people to quickly create 3D models using photogrammetric methods this. Although the resulting model often still contains loopholes, so additional cleaning with software like MeshLab, netfabb, or MeshMixer is often still needed.

Photogrammetry is also commonly used in collision techniques, especially with cars. When litigation for accidents occurs and the engineers need to determine the exact existence of deformation in the vehicle, it has been common for several years have passed and the only remaining evidence is photos of scenes of accidents taken by the police. Photogrammetry is used to determine how many cars in question are deformed, which corresponds to the amount of energy required to produce the deformation. Energy can then be used to determine crucial information about accidents (such as speed at the time of impact).