Almost all previous Augmented Reality (AR) systems work indoors. Outdoor AR systems offer the potential for new application areas. However, building an outdoor AR system is difficult due to portability constraints, the inability to modify the environment, and the greater range of operating conditions. We demonstrate a hybrid tracker that stabilizes an outdoor AR display with respect to user motion, achieving more accurate registration than previously shown in an outdoor AR system. The hybrid tracker combines rate gyros with a compass and tilt orientation sensor in a near real-time system. Sensor distortions and delays required compensation to achieve good results. The measurements from the two sensors are fused together to compensate for each other's limitations. From static locations with moderate head rotation rates, peak registration errors are ~2 degrees, with typical errors under 1 degree, although errors can become larger over long time periods due to compass drift. Without our s...