In this article we will analyse some of the existing AR-based applications, starting with those that were developed by the U-Academy Project partners and that have mainly an educational purpose.

One of the basic elements of AR, is the visualisation device. In most situations a modified HMD, that includes one or more front-facing cameras.

These HMDs, are typically composed by one or two LCD or OLED displays, sometimes a pair of earbuds or headphones, and an Inertial Measurement Unit (IMU).

The IMU can be composed by  accelerometers, gyros and magnetometers, being the latter only available in some models.

In most of current AR applications the interaction is limited to the motion of the handheld device or HMD as a way to change the point of view with respect to the scene that contains the virtual elements. We can say that for several cases this is sufficient if the objective is only the visualisation of those elements. What happens when the user wants to select different types of information or eventually interact with the virtual elements to modify their behaviour or even use them as control inputs for some physical system. The handheld approaches can make use of the touchable interface to select, open menus and select options of these elements. 

Conversely, the HMD-based applications are typically hands free approaches and selections or interactions must be made using buttons on the helmet itself, or using a gamepad or other handled device. We can say that there is more freedom for the interaction as the surrounding environment remains visible, keyboards, button pads, or any traditional device may be used.

Read more: Interaction issues in AR