Carrier phase differential GPS/INS positioning for formation flight

A method for implementing and testing algorithms for combining differential carrier phase GPS and an INS system for formation flight of two NASA F-18 aircraft is presented. A computer architecture based on the PC-104 AT bus and commercial, off-the-shelf components is used for implementing the algorithms. Processing the carrier phase measurements using an INS with online calibration by a tightly coupled extended Kalman filter should provide relative position measurements to within 10 cm without the use of a stationary base station. Two methods are suggested for solving the integer ambiguity problem. The method of Farrell et al. uses hypothesis testing combined with least squares processing to determine the initial integer values. A second method uses the multiple model adaptive Kalman filter with improved convergence properties to estimate the integers. In order to test these algorithms and hardware, a hardware in the loop simulation using an IEC GPS Constellation Simulator will be constructed to validate accuracy claims