# 3D Reconstruction of Cultural Heritage Sites as an Educational Approach. The Sanctuary of Delphi
## 4 Materials and Methods
### Construction of the 3D Environment  
In order to build three-dimensional digital models of a site like an archaeological site, there are several tools and techniques that, with the appropriate and necessary input of real or even approximate data, outputs 3D models to different file types. The 3D models produced are the final product for importing to gaming engines for educational applications [64]. The 3D environment of the application presents the site of Delphi Sanctuary enhanced with reconstructions of its most important buildings and monuments. The data and models used were obtained from three sources, as explained in more detail in the following paragraphs: (a) the Delphi archaeological site and museum that provided models of the main buildings, (b) the use of photogrammetry technique and software for detailed terrain texture and additional momuments, and (c) GIS data for the terrain model. The application has been built in Unity, a popular engine for creating interactive 3D applications and games. Initially, the digital terrain model has been imported from GIS data using SketchUp software with Oob Terrain add-on. The terrain was sized 2 km \(\times\) 2 km. The texture of the terrain has been created with a series of photos taken from helium-filled balloon. The balloon (Figure 2) had rope-mounted fixed aluminum platforms equipped with a digital camera, Canon EOS 50D DSLR. On-site photos capturing required a flight plan of about 10-100 m [65]. Photo capturing from the balloon was performed as part of the Delphi4 Delphi project [66], with the aim of collecting images suitable for the photogrammetry method using the Structure from motion (SfM) technique [67]. The main goal of the project is to capture detailed 3D images of the major archaeological monuments at Delphi and artefacts in the Delphi archaeological museum in order to contribute to the 3D reconstruction of the sanctuary in support of research, conservation, tourism and education [65]. For the creation of the 3D model of Delphi's archaeological site, more than 13,000 photos were taken, and the model produced by the laboratory of the University UCSD (University of California, San Diego, CA, USA) partner in Delphi4 Delphi, had size \(\sim\)4 GB. The 3D model was then simplified, and the final model was used in our Virtual Tour application (Figure 3). Figure 1: Methodology steps. From the web site of the Delphi Museum, 8 reconstructed 3D models of buildings were downloaded and placed along the sacred road (from the entrance of the archaeological site to the ancient theater), using a map of the French Archaeological School. The files used were free for both copy and redistribution, as well as for conversion to any medium or format, if they were not for commercial use (Figure 4). Figure 3: Terrain from Sketchup and balloon inside Unity 3D (@ Authors). Figure 2: The helium-filled balloon for aerial photography (Kingfisher Aerostat) (@ [PERSON] 2016). In addition to 3D buildings, the ancient theater and three more monument models were added to the virtual tour. The Omphalos symbolizing the center of the earth, the statue of the [PERSON] ([PERSON]), which is undoubtedly the most famous of the tributes to [PERSON] and the column with the Dancers. To create the 3D models of the above exhibits from the Delphi Museum and also of the ancient theater, thousands of photos were taken and Agisoft's PhotoScan software was used to create 3D models of images using the SfM (Structure from Motion) photogrammetry [65] as part of the Delphi4 Delphi project. For the navigation in the virtual environment, Unity's First-Person Controller (FPS) was used. There was no time limitation in browsing, as a basic feature of a virtual space is that it allows users to move to their own pace [68]. For better contacting with the virtual space, a mini map was created in the upper left corner of the screen as well as a compass which can be activated for observing the orientation of the buildings. Adding code to the software was done in a variety of ways.