Development of a GPS-aided inertial platform for an airborne scalar gravity system

Abstract

The development of a OPS-aided inertial platform for an airborne scalar gravity system is described in this dissertation. Damping Schuler oscillations of an airborne inertial platform and achieving a levelling accuracy of a few arc seconds are the main objectives. System errors are analyzed and modelled. Two methods for inertial platform levelling loop stabilization by OPS velocity are analysed and compared, one using an open loop design, the other a closed loop design. Algorithms for platform initial alignment, gyro drift and navigation, which are fundamental to the OPS-aided inertial platform, have been designed and implemented. A series of tests on kinematic double difference OPS position and velocity errors have been performed using a precise positioning stage as a reference. A radio data link system is designed to eliminate Selective Availability (SA) effects on real-time OPS velocity. Accuracy and time latency of the real-time DOPS system are tested. To evaluate algorithms and methods, platform systems are simulated, and both methods of platform stabilization are applied to flight data taken by the ITC-2 inertial platform and a set of Trimble 4000 SSE receivers on board of a Cessna 310 twin engine air plane. Both theoretical analysis and results of simulation and flight test indicate that the Schuler oscillations of an inertial platform can be damped by OPS velocity to an accuracy of a few arc seconds and that the platform levelling accuracy can thus be significantly improved.