Terrain-Aided Navigation Test Results in the AFTI/F-16 Aircraft

Abstract

Sandia National Laboratories has developed a low-level attack aircraft terrain-aided navigation algorithm for the Air Force Wright Aeronautical Laboratories, Avionics Laboratory. This algorithm is based on the Sandia Inertial Terrain-Aided Navigation (SITAN) approach to terrain-aided navigation that was initially formulated at Sandia in the mid-1970s. Extended Kalman filter theory is used to provide essentially continuous terrain-aided navigation through estimation of inertial navigation system errors from radar altimeter ground clearance measurements and on-board digital terrain elevation data (DTED). The SITAN algorithm is integrated into the Advanced Fighter Technology Integration (AFTI)/ F-16 aircraft, and called AFTI/SITAN to distinguish it from other SITAN designs. AFTI/SITAN performance, as determined by Air Force tracking radar during real-time testing in the AFTI/F-16 aircraft at Edwards Air Force Base from September 1986 through April 1987, is presented. Required performance is less than 100 m median horizontal radial error over 200 nmi trajectories that are flown over gently rolling terrain with available DTED. The flight data support the conclusions that AFTI/SITAN reliably determines aircraft position within an initial 0.5 nmi, CEP horizontal position error, and tracks aircraft horizontal position with an accuracy of 75 m median radial error using DTED supplied by the Defense Mapping Agency. Although accurate estimation of absolute altitude is not required for proper SITAN operation, altitude is estimated with less than 17 m root-mean-square error.