GPS-BASED ATTITUDE FOR AIRCRAFT

GPS was used with ultra-short baselines (2-3 carrier wavelengths) in a triple antenna configuration to obtain aircraft attitude in real time. Through algorithm selection and error source calibration, accuracies of 0.1°, 0.15° and 0.2° rms were obtained for pitch roll and yaw respectively. The accuracy and robustness of the system was enhanced by combining the ultra short-baseline GPS attitude solution with an attitude solution derived using inertial sensors. Both inexpensive automotive grade rate gyros and tactical grade inertial sensors were tested. The solid state auto grade gyros allow coasting through temporary GPS outages lasting 2 minutes with attitude errors less than 6 degrees. The tactical grade inertial sensors use the GPS primarily for initial alignment and are able to coast for up to 30 minutes durring AGPS outage. The combined GPS-inertial system has a 20Hz output sufficient to drive glass cockpit type displays. A prototype system was built and flight tested in a Beechcraft Queen Air. The system installed and flight tested in the Queen Air compares favorably to the performance of the existing vacuum driven instruments. It is currently being used in ongoing research at Stanford with futuristic high resolution displays[1].