Page 130 - AC/E Digital Culture Annual Report

130can be processed digitally to achieve elevations, cross-sections, pro les and maps of damage that allow a diagnostic study to be performed over a period of time.The Spanish company Factum is notable for its long experience and active work in data acquisi- tion using digital scanning and photogrammetric techniques speci cally for heritage sites or objects. Its website contains a quick guide34 for sector professionals on the process and devices used for this task.Digital photogrammetry consists in taking measurements of an object from photographs. To carry out a high-precision photogrammetric measurement, the camera must capture a setof digital images that make up the photogram- metric data. It is also important to follow a methodology that establishes the process and guides the user in con guring, positioning and pointing the camera at the object in question (as, especially in the case of cultural heritage, we are dealing with highly heterogeneous elements) so that the information supplied to the processing software is as useful as possible. This will reduce to a minimum any possible inaccuracies in the resulting measurements, ensuring high-quality results in 3D models based on a limited number of photos taken by standard digital cameras and in a relatively short period of time.Recent technological advances in digital cam- eras, capturing devices, processors and com- putational techniques make photogrammetry well-suited to digitally documenting heritage. The variety of techniques and the number of applications of photogrammetry and related processes have increased exponentially in the eld of heritage. In particular they have found a major ally in drones, giving rise to what is called aerial photogrammetry, which enables data to be obtained both from large outdoor spaces and from interiors that are di cult to access.Although we are discussing photogrammetry here, laser scanning has also made signi cantprogress in digitally recording heritage, proving to be a tool with major potential. Laser scanners are devices that acquire the spatial coordinates of a particular structure or object systematically and in real time, obtaining su cient data to create a point cloud as the basis for producinga digital three-dimensional model. A particular feature of laser scanners is that they provide truly precise information about the relief and texture of a surface, and this makes them espe- cially well-suited to examining and documenting cultural objects.Roughly speaking, depending on the element it is wished to scan, one type of device or another is used. The long- and medium-distance system LiDAR (light detection and ranging) is used to record the measurement of large surfaces or objects, whereas short-range scanners are ideal for recording the details of an object’s surface from a distance of less than one metre. The combination of both types of scanner allows a more detailed and accurate digital model to be obtained. Work carried out on heritage using laser scanners is therefore giving rise to more detailed analyses of heritage elements, resulting in new ideas and greater knowledge of their history.Until a relatively short time ago, the application of photogrammetric and 3D laser scanning tech- nologies was limited to institutions and compa- nies with su cient capital and resources to fund the learning methods and the devices required for applying these techniques to heritage. How- ever, in recent years the situation has startedto change as costs have gradually decreasedand devices, methodologies and software have proliferated. As a result these technologiesare among the resources most widely used by enthusiasts and sector professionals interested in documenting and digitising heritage.Colonial church of Ekab (Mexico)Collaboration between the University of Cali- fornia (San Diego, California) and the Instituto1. DOCUMENTATION, DIAGNOSIS AND CONSERVATIONThe use of digital technologies in the conservation, analysis and dissemination of cultural heritage