We describe and evaluate a new tracking concept for outdoor Augmented Reality. A few mobile beacons added to the environment correct errors in head-worn inertial and GPS sensors. We evaluate the accuracy through detailed simulation of many error sources. The most important parameters are the errors in measuring the beacon and user’s head positions, and the geometric configuration of the beacons around the point to augment. Using Monte Carlo simulations, we identify combinations of beacon configurations and error parameters that meet a specified goal of 1m net error at 100m range. CR Categories: H.5.1 [Multimedia Information Systems]: Artificial, augmented and virtual realities. C.4 [Performance of System]: Performance attributes. J.7 [Computers in Other Systems]: Military