Accurate positioning in an inertial-based automatic flight inspection system using differential global navigation satellite systems

The paper presents the simulation and flight test results of a position estimation technique which integrates differential global navigation satellite systems (DGNSS) and an inertial navigation system (INS) in the final approach flight inspection mission. The purpose of an automatic flight inspection system (AFIS) is to verify performance and calibrate ground-based aircraft navigation and landing aids. This mission requires that the flight inspection platform have a reference position estimate significantly more accurate than that of the facility under inspection. In Sierra Research´s inertial-based flight inspection system, a square root Kalman filter estimates the navigation errors in real time and a modified Bryson-Frazier smoother improves these estimates immediately post profile. At present, during the final approach, the Kalman filter is updated by either pilot or camera observations of the runway stripes, and laser altimeter measurements. The study shows that appropriately accurate DGNSS updates can replace one or both of the current methods. A simulation analysis was performed to predict the accuracy required of a DGNSS update to an inertial system. Some of these predictions were flight tested on a business jet aircraft during the summer of 1993, using a differential global positioning system (DGPS) receiver capable of both code and carrier phase observation. The results of the simulation and flight test are presented