Presented at SatNav 2003

This paper presents the results of augmenting an INS/GPS navigation system with a barometric altimeter for an autonomous Uninhabited Aerial Vehicle (UAV). The INS/GPS system was designed using a loosely coupled integration architecture that incorporates the GPS navigation solution. The GPS typically has a poor accuracy in the vertical channel due to satellite geometry and atmospheric effects. Even worse, the vertical channel is vulnerable to faults due to its inappropriate dynamic model coupled with the frequent loss of satellites when the UAV would bank. From the real-time flight tests, huge GPS faults were observed in the vertical axis, causing the INS/GPS navigation system to become unstable. By augmenting the baroaltimeter data, the vertical channel can be stabilized under GPS fault conditions. A ten-state Kalman filter was designed to optimally blend the INS with GPS and baro-altimeter. The results using the flight data show that the baro-altimeter augmented INS/GPS navigation system can provide more reliable and accurate navigation solutions under high maneuvering environments.