In this section, we will look at one of the major approaches for mobile AR and sensor-based AR (see Chapter 1, Augmented Reality Concepts and Tools), which uses global tracking. Global tracking refers to tracking in a global reference frame (world coordinate system), which can encompass the whole earth. We will first look at the position aspect, and then the location sensor built on your phone that will be used for AR. We will learn how to retrieve information from it using the Android API and will integrate its position information into JME.
So we need to track the position of the user to know where he/she is located in the real world. While we say we track the user, handheld AR applications actually track the position of the device.