In order to understand the question of Tracker Accuracy Testing, one must first understand some of the complexities related to Tracker Accuracy Requirements. For example -- if a tracker system is said to have an accuracy of 2 miliradians -- does anyone know what this really means? And likewise, does anyone have the required test environment to accurately test such a specification? Under what conditions is the system accurate to 2 mR? In the lab? In an Aircraft, but on the ground? Airborne, but in a static situation? When looking forward through the HUD? All-Aspect, but in a small 'Motion Box?' -- These questions are only a few from a long list of variables that can change the meaning of 2 mR, or any accuracy number, by an order of magnitude or more. Once the performance or accuracy specification has been established, assuming the definition is clear and indisputable, the Testing Methodology should be defined as part of the system requirements. The cost of testing also comes into play and in many cases is the main constraint for determining the level of testing. This is true for any high-tech/high performance system, and especially for Helmet Mounted Trackers.