In-flight detection of errors for enhanced aircraft flight safety and vertical accuracy improvement using digital terrain elevation data with an inertial navigation system, global positioning system and radar altimeter

This dissertation discusses integration architectures using digital terrain elevation data (DTED) with an inertial navigation system (INS), a global positioning system (GPS) and a radar altimeter. Two integration architectures are considered: DTED with INS, GPS and radar altimeter for aircraft vertical accuracy improvement during the final approach; and DTED with kinematic GPS (KGPS) and a radar altimeter for enhanced aircraft flight safety. Error models were generated and verified with flight-test data. High-fidelity simulation was used to investigate vertical accuracy improvement. Improvement was found to be 1.2 meters, a reduction of 28.6% in the vertical error. Flight testing was performed to assess the feasibility of enhanced flight safety. Reasons for enhanced flight safety are twofold: (1) the ad-hoc integration of terrain elevation data into the cockpit conceivably may create scenarios which lead to accidents because the cockpit display is quite realistic, and (2) reduction of controlled flight into terrain (CFIT). The radar altimeter is the principle sensor used to compare navigation outputs with publicly available DTED. Results show that it is feasible to define an operationally useful probability of agreement, P_a, among KGPS, DTED and the radar altimeter, by using a mean-square-difference test statistic. This probability of agreement can be used to warn the pilot if the terrain depiction does not agree with the navigation solution provided by KGPS, thus enhancing flight safety.