Terrain-aided altitude computations on the AFTI/F-16

A variety of barometric and inertial-based altitude channel implementations has been flight-tested on the US Air Force´s advanced fighter technology integration (AFTI) F-16. Previous mechanizations of the altitude channel are briefly reviewed, together with flight test data describing their performance. More recently, a color moving map system with an associated digital terrain elevation database has been added to the AFTI avionics suite and is being integrated into the weapon delivery system. This digital map system includes an implementation of the Sandia inertial terrain-aided navigation (SITAN) algorithm. The design, mechanization, and preliminary flight testing of a new altitude channel implementation are described. This mechanization automatically corrects for pressure altitude bias and drift, while referencing the altitude estimate to the terrain database which forms the common reference grid for low-level maneuvering flight, targeting, and weapon delivery