Magnetic Heading, Achievements and Prospective

The availability of continuous GPS updates during flight significantly mitigates inertial sensor performance requirements, allowing for high accuracy positioning using low-cost, small MEMS IMU-based Inertial Navigation Systems ( INS). Meanwhile, employment of a low-accuracy MEMS gyro reduces the accuracy of on-board heading information and completely eliminates the heading self-initialization capability of INS, because even a high-performance MEMS gyro with composed bias stability of 10 degrees/hr over required temperature range (yet to be achieved) cannot be used in gyro-compassing mode due to an unacceptable (over 30 degrees) heading error. Significant progress in fluxgate magnetometry has resulted in high accuracy magnetic heading information in the on-board environment. Acceptable for numerous applications heading accuracy can be achieved by employment of a simple, highly reliable, relatively small and low-cost fluxgate magnetometer-based magnetic compass. To achieve equal heading accuracy in gyro-compassing mode, an expensive, relatively large, near-navigation-grade INS should be employed. This paper presents an analysis of fluxgate magnetometer based magnetic compass errors on the ground and in the flight. Numeric estimation of potential accuracy showed that a magnetic heading accuracy of better than 0.3 degrees can be achieved on the ground for latitude range of +/- 62 degrees (88.3% of the Earth's surface). Real-time correction for daily variation of the Earth's magnetic field allows for achievement of the same accuracy for latitudes up to +/- 73 degrees (97% of the Earth's surface). In flight, heading accuracy better than 0.4 degrees can be expected for latitude +/- 62 degrees, and better than 0.6 degrees for latitude +/- 73 degrees. Presented in the paper results can be beneficial for the development of precision magnetic compasses for a low-cost MEMS INS/GPS based Integrated Navigation Systems, where a low accuracy MEMS gyro doesn't support heading initialization and magnetic compass is the only choice.