# A Review on Augmented Reality in Education and Geography: State of the Art and Perspectives
## 7 Future Developments  
Based on the comparative analysis performed in Section 6, a number of future improvements can be proposed and discussed. First, when looking at the computing devices the Illuminating Clay, SandScape, and AR Sandbox use, it can be observed that all of them use a personal computer, such as a laptop. Because it is quite inaccessible to always have a laptop that can be connected to the sandbox or to leave a laptop connected all the time, it can be easily replaced by a development board, such as a Raspberry Pi. The Raspberry Pi produces several versions, such as Raspberry Pi Model 5, Raspberry Pi 500, which is an all-in-one keyboard-PC, Raspberry Pi Pico, or Raspberry Pi Zero. For this type of application, a more powerful model is needed, because a lot of hard computations must be performed, and it needs to be able to create and display through the projector the topographic map. To achieve this, the Raspberry Pi Model 4B can be used. So, by using this type of development board, the implementations of AR Sandbox become easier to use and to be transported from class to class, without worrying about the computing device, as it fulfils the same tasks as a laptop, having almost the same performance. Additionally, the water simulations that are implemented as functionalities in the versions of AR Sandbox use the Navier-Stokes equation in real time (Equation (5)). Although by using this equation, the water simulations are highly detailed and have a high degree of accuracy, this can be a heavy task for a laptop, and even a more difficult task for a Raspberry Pi, as it does not have that many computing capabilities. Also, because there are partial differential equations (PDEs), the computations for the Navier-Stokes equation can quickly load the CPU, which is not desired in this kind of application [39]. To solve this problem, [PERSON] proposes a solution [40], where the height map for fluid simulations is based on the heights at each point, which can be obtained from the DEM model or from the depth image. Then, having the heights, the difference between each neighboring point can be calculated, thus obtaining a simulation of how the water would flow from high points to lower points on the map. Of course, this is rather an approximation to the Navier-Stokes equation, but by using this method, the development board or the laptop can compute the water simulation much faster, as this is an iterative algorithm. To obtain the flow of water, Equation (6) can be used, where Height(x,y) is the total height of the terrain at the point (x,y), summed up with the total water height at the same point. \[ \begin{array}{c}\text{flow}=(\text{Height}(\text{x},\text{y})-\text{Height}(\text{x}+1,\text{y}))+(\text{Height}(\text{x},\text{y})-\text{Height}(\text{x}-1,\text{y}))\\ +(\text{Height}(\text{x},\text{y})-\text{Height}(\text{x},\text{y}+1))+( \text{Height}(\text{x},\text{y})\\ -\text{Height}(\text{x},\text{y}-1))\end{array}  \tag{6}\]  
To update the water height map, each of the already available values in the water height map is multiplied by a coefficient that represents the flow speed, determining how fast the water is moving on the topographic map. Finally, in order that there are no negative values for the flow of the water, the whole water height map is checked using the following equation (Equation (7)):  
\[\text{water}_{\text{height}}=\text{max}\Big{(}0,\text{water}_{\text{height}} \Big{)} \tag{7}\]  
Another improvement that can be brought to the versions of AR Sandbox would be to implement more hand recognition functionalities. For example, if the students or the teacher use their hands in a pinch mode over the sandbox, the camera (B) would recognize the form of their hand and would detect the point that they are showing. Thus, at that specific selected point, the elevation would be shown on top of the topographic map by using the projector (A), as presented in Figure 12.  
Figure 12: Representation of point detection.