Existing commercial technologies do not adequately meet the requirements for tracking in fully-enclosed Virtual Reality displays. We present a novel six degree of freedom tracking system, the Hedgehog, which overcomes several limitations inherent in existing sensors and tracking technology. The system reliably estimates the pose of the user's head with high resolution and low spatial distortion. Light emitted from an arrangement of lasers projects onto the display walls. An arrangement of cameras images the walls and the two-dimensional centroids of the projections are tracked to estimate the pose of the device. The system is able to handle ambiguous laser projection configurations, static and dynamic occlusions of the lasers, and incorporates an auto-calibration mechanism due to the use of the SCAAT (Single Constraint At A Time) algorithm. A prototype system was evaluated relative to a state-of-the-art motion tracker and showed comparable positional accuracy (1-2 mm RMS) and significantly better absolute angular accuracy (0.1 deg RMS).