Design and test of a synergistic interferometric GPS-INS

Interferometric GPS is a technique which employs measurements of carrier phase difference to provide highly accurate relative position measurements. Interferometric GPS uses the measurements at multiple antennae mounted on rigid baselines to provide orientation information. While GPS provides measurements which are stable over the long term, these measurements have relatively low bandwidth with respect to an inertial system and can be denied by obscuration or jamming of the signal from the satellite. A tightly coupled combination of an interferometric GPS system and a low cost inertial system provides an affordable high bandwidth attitude determination system. The inertial system generates wide bandwidth data with the GPS providing long-term error bounding. This paper discusses the design and test of a prototype system using a Litton LN-200 fiber optic gyro inertial navigation system (INS) and two NovAtel C/A code carrier phase tracking GPS receivers. The system provides continuous position, velocity, heading and attitude information which is more accurate than standalone INS performance.