Instantaneous GPS attitude determination

The author describes a procedure for instantaneous GPS (Global Positioning System) attitude determination, i.e., a solution for the GPS integrated carrier Doppler wavelength ambiguities using only measurements at a single epoch. Most previous techniques for solving the phase ambiguity problem have required some form of time history processing relying on GPS satellite and/or user motion to provide enough geometry change to eliminate false solutions. The algorithm described assumes three nonlinear antennas and integrated carrier Doppler measurements from four or more satellites. Double-difference processing provides at least three independent observables for the two antenna separation vectors to compute the three attitude Euler angles. The results obtained also suggest that arbitrarily large separations can be resolved since unambiguous carrier-smoothed pseudorange measurements could provide a coarse measurement with an accuracy falling within the resolution range of the algorithm presented