# A Review on Augmented Reality in Education and Geography: State of the Art and Perspectives
## 6 Augmented Reality Sandbox
Unfortunately, the frames are not movable, which makes them have a lower maneuverability index. Regarding the laser scanner used, for implementing Illuminating Clay, the authors used a high precision 3D laser scanner, Minolta Vivid-900. Even though this type of laser scanner is a high-end one, it is amazingly easy to use and to mount, making it a great entry point in the domain of high detail laser scanning. In the case of SandScape, the authors used an IR camera that detects the intensity of the IR light that is being dissipated in the medium used. For the last implementation presented, AR Sandbox, the authors used the sensor of an Xbox 360 Kinect because it is a sensor available to everyone and easily mounted and connected to a computer. All of the implementations use IR light so that the camera can detect the model that is being scanned. One of the main differences between the three methods of scanning is the accuracy of the resulting model. Because the Illuminating Clay used a high-end laser scanner, Minolta Vivid-900, this implementation has the highest accuracy, \(\pm\)0.1 mm. Next is the SandScape implementation, being able to have an error of only \(\pm\)1-3 mm. In the end, the worst accuracy was obtained with the Xbox 360 Kinect, having an error of \(\pm\)2-4 mm. For testing purposes, the height of the laser scanners was set to 2 m. Also, if for the Minolta Vivid-900 and for the Xbox 360 Kinect only the height would make a difference to the accuracy of the scanned model, the IR camera of the SandScape implementation would vary the accuracy not only because of the height but also because of different factors like: the thermal properties of the material used for simulating the landforms, the quality of the camera or the wavelength of the IR light. Everyone used a projector to show the topographic map over the material used for each of the AR Sandbox implementations. The material used for modeling and simulating the topographic map was different for each of the three versions. For the Illuminating Clay application, the authors used a clay that is moldable, and it is easy for the students to use. Nevertheless, the clay is easy to break apart and, thus, new clay is needed. For SandScape, \begin{table}
\begin{tabular}{c c c c} \hline
**Component** & **Illuminating Clay** & **SandScape** & **AR Sandbox** \\ \hline Maneuverability & Medium & Low & Low \\ \hline Laser Scanner & Minolta Vivid-900 & IR camera & Xbox 360 Kinect \\ \hline Method of scanning & IR light & IR light & IR light \\ \hline Accuracy of scanning & \(\pm\)0.1 mm & \(\pm\)1–3 mm & \(\pm\)2–4 mm \\ \hline Projection type & Projector & Projector & Projector \\ \hline Material used & Clay & Glass beads & Sand \\ \hline Computing device & Computer & Computer & Computer \\ \hline
3D model type & DEM & DEM & Depth image \\ \hline Material for & & & \\ \hline Number of & & & \\ \hline Robustness & Low & Medium & High \\ \hline Price & High & Medium & Low \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison between Illuminating Clay, SandScape, and AR Sandbox. the authors used glass beads, which are 1 mm in diameter. Even though this seems like a great option, they might be dangerous to young students as they are easily ingested and could be choking hazards. Moreover, the glass beads could become increasingly more opaque because of the friction from the modeling, and thus, the IR light density would decrease, resulting in erroneous simulations. For AR Sandbox, the authors used sand, which can be a great alternative for both clay and glass beads. It is easily moldable, easy to replace, and not so dangerous to students. Because of the materials used, the robustness of the applications was considered low for Illuminating Clay and too high for AR Sandbox. The materials used to enclose the sand were a box made out of wood, whereas for the glass beads, a glass box was needed. For Illuminating Clay, the material on which the clay stands could be made from anything, as only the clay is captured.