True position is a geometric dimensioning and tolerancing (GD&T) term that describes the actual location of a feature relative to its theoretically perfect location. It is important to check true position in order to ensure that parts are assembled correctly and function properly.
There are a number of different ways to check true position, including using a coordinate measuring machine (CMM), a vision system, or a laser tracker. The best method for checking true position will vary depending on the specific part and the required accuracy.