Precision Attitude Determination Using a Low Grade Gps-aided Inertial Measurement Unit

Precision attitude determination is a key requirement for precision targeting. Current targeting systems use range and bearing to target (relative to the Forward Observer’s GPS coordinates) to derive the target coordinates. The accuracy of these coordinates is currently limited by the accuracy to which the bearing to target can be observed. Conventional methods of determining attitude include gyrocompassing, GPS interferometry and magnetic sensors. Existing portable targeting systems provide bearing to an accuracy of 10 mrad which introduces 10 m of position error in target coordinates at a range of 1 km. NAVSYS have developed a precision GPS/inertial attitude determination method that enables 1 mrad pointing accuracy to be provided using low cost (missile-grade) inertial instruments. Test data presented in this paper shows that this method provides better than 30 times improvement in accuracy over conventional gyrocompassing methods.