# The Usage of Virtual and Augmented Reality in Underwater Archeology
## 3 Virtual and Augmented Reality Technologies
### Creating Virtual or Augmented Reality Applications for Underwater Archeology
These methods, however, are not very popular in underwater archeology and serve rather auxiliary functions. For example, electrical resistivity tomography (ERT), which is based on measuring the differences in the electrical properties of the medium, was used, among other methods, to collect measurements of a barge called Crowie, located in the town of Morgan on the Murray River in southern Australia, in order to create its 3D visualization [49]. This method is rarely used in underwater archaeology. In the second stage, various techniques are used to recreate the shape and build models for later use in a virtual application [55; 56]. The most frequently used methods in this area include the following [32]:  
* Shape from texture (SfT)--the source of information is photos of objects that are processed by algorithms analyzing the textures covering the objects. * Shape from focus and defocus--this method involves extracting depth from many photos taken with different focal lengths. Algorithms analyze both the shape and brightness of the object. * Shape from motion (SfM)--the shape of an object is recreated using its motion recorded by a camera. Currently, this is probably the most frequently used method in underwater archeology to create a three-dimensional visualization of objects [47]. * Shape mapping from shades of gray (shape from shading, SfS), known as photo-clinometry--algorithms reproduce the shape using the degree of shading of various parts of the object in a two-dimensional image, taking into account the direction of incidence of light. This is also one of the most commonly used methods today. The next step after building a three-dimensional computer model of an object is to select the output formats available for viewing the results. These may include the following, among others: animations; 3D graphics using applications such as AutoCad or 3D studio; panoramas and three-dimensional photos, e.g., using the QTVR format (QuickTime dedicated to VR); VR simulators, e.g., using the VRML programming language; and finally, applications in online gaming environments, e.g., Unity3D [57]. The selected output format will depend on the purpose of use of the resulting images, their recipient, and the equipment and display software to which we want to dedicate the results of the visualization [15; 32]. At the stage of preparing an appropriate form of information transfer using VR or AR, the choice of content display technology is equally important. Most devices available on the market offer only visual and auditory simulations. The most popular VR solutions can be divided into two groups: head-mounted displays, the so-called HMD; or the so-called environment CAVE, which is implemented on the scale of a room or part of it [51; 57]. In both cases, it is possible to stimulate other senses, e.g., smell or touch, but they are relatively rarely used and usually require more expensive solutions [57]. In the field of AR and MR, mobile devices are used in many cases to superimpose a virtual simulation on the real world [57].