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 1 m net error at 100 m range.

"Free Flight" will change today's air traffic control system by giving pilots increased flexibility to choose and modify their routes in real time, reducing costs and increasing system capacity. This increased flexibility comes at the price of increased complexity. If Free Flight is to become a reality, future air traffic controllers, pilots, and airline managers will require new conflict detection, resolution and visualization decision support tools. The paper describes a testbed system for building and evaluating such tools, including its current capabilities, lessons we learned and feedback received from expert users. The visualization system provides an overall plan view supplemented with a detailed perspective view, allowing a user to examine highlighted conflicts and select from a list of proposed solutions, as the scenario runs in real time. Future steps needed to improve this system are described.

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 /spl sim/2 degrees, with typical errors under 1 degree, although errors can become larger over long time periods due to compass drift. Without our stabilization, even small motions make the display nearly unreadable.