of other digital surveying methods. Cultural heritage Cultural heritage is present everywhere. Its structural control, documentation and conservation is one of humanity's main duties (UNESCO). Under this point of view, SfM is used in order to properly estimate situations as well as planning and maintenance efforts and costs, control and restoration. Because serious constraints often exist connected to the accessibility of the site and impossibility to install invasive surveying pillars that did not permit the use of traditional surveying routines (like total stations), SfM provides a non-invasive approach for the structure, without the direct interaction between the structure and any operator. The use is accurate as only qualitative considerations are needed. It is fast enough to respond to the monument’s immediate management needs. The first operational phase is an accurate preparation of the photogrammetric surveying where is established the relation between best distance from the object, focal length, the ground sampling distance (GSD) and the sensor’s resolution. With this information the programmed photographic acquisitions must be made using vertical overlapping of at least 60% (figure 02). Furthermore, structure-from-motion photogrammetry represents a non-invasive, highly flexible and low-cost methodology to digitalize historical documents. See also 3D reconstruction from multiple images Bundle adjustment Comparison of photogrammetry software Computer stereo vision Epipolar geometry Kinetic depth effect Match moving Motion field Motion parallax Semi-global matching Simultaneous localization and mapping Stereophotogrammetry Tomasi–Kanade factorization 2D to 3D conversion Further reading Jonathan L. Carrivick, Mark W. Smith, Duncan J. Quincey (2016). Structure from Motion in the Geosciences. Wiley-Blackwell. 208 pages. References Geometry in computer vision Emerging technologies 3D imaging Photogrammetry Motion in computer vision