# A Review on Augmented Reality in Education and Geography: State of the Art and Perspectives
## 3 Augmented Reality in Education
In the second stage, the application was improved to capture the real scene with the aid of a TV camera, and the image was superimposed on a flat display. Then, in the last stage, the AR device used an optical see-thru HMD, eliminating the need to use a TV camera. An optical see-thru HMD is a head-mounted 3D display in which the real world is also available optically when observing the virtually generated one. The final device was designed to have a tracker, an enhanced reality setup, and an optical see-thru HMD. The tracker is composed of one transmitter and three receivers, each of the receivers being placed on the arm: one near the humerus and two at both ends of the forearm. By placing them in this way, the 3D model can be generated on the computer by taking the position of the sensors. Because of the complicated hardware, the AR applications were costly, and the universities and schools did not want to invest in such devices. Also, the hardware and the applications as a whole were really hard to use, and would need the users to extend their knowledge too much into this domain to work with such technology. Moreover, the ease of using the hardware was very low, and so, the users' experience quality was also low. By putting together the disadvantages of cost and usability, it can be observed that the learning process was obstructed by the complexity of the AR applications. The second generation of AR applications, the Application-based AR, tried to come up with a solution to the problems the AR world met in the first generation. Because of the rapid development of mobile phones and software technologies, the solution was to deploy mobile-based AR applications, such that the applications were accessible to anyone, anywhere. Also, the costs of purchasing these applications were lowered drastically, as there was no need to buy expensive hardware. Additionally, the users did not need to invest a great number of hours into learning how the software works, like in the first generation, as there were available SDKs, game engines, and libraries that eased the learning curve. Furthermore, in this period, the AR applications in the educational domain began to improve to the point that five directions were proposed: AR books, AR gaming, discovery-based learning, object modeling, and skills training. The most important direction in the educational field among the five directions listed above is the AR book [16], because of the ease with which, not only the students, but also the teachers, can use the applications to learn and to teach a new domain. For example, one of the most used AR book applications is the MagicBook, developed by [PERSON] [17]. The application works by using a handheld AR display (HHD) that is composed of a switch, a compass, and a camera. After the HHD is turned on using the switch, the device starts and looks for a marker present in the book. After the marker is recognized by the HHD, it is compared with certain templates in the memory of the device, and finally, the virtual object replaces the marker. The role of the compass is to detect the pose (position and orientation) of the HDD and, thus, of the user, such that the virtual object is shown in the right pose, oriented toward the user's face. One of the most important advantages of using the MagicBook is that it cannot only  
Figure 6: Time domain of the development of AR in education. be used as an AR device, but also students and teachers can read it without using any AR application, being a standalone book. The last generation is the Smart Glasses Web-Based AR applications. This generation tries to combine three elements: smart glasses, WebAR, and AI. The smart glasses are a type of device, like Oculus Rift or, more recently, Apple Vision Pro, that allows the user to connect to the internet and to visualize all the information, while he can still see and be connected to the real world. The WebAR applications address the problem of AR mobile applications not being downloaded or being uninstalled after just a few uses.