Performance Improvement of an Inertial Navigation System Based on FOG and SA Using a Two-Step Indirect Calibration Method

This paper presents a two-step indirect calibration method to enhance the performance of a tactical-grade Inertial Navigation System (INS) using Fiber Optic Gyroscope (FOG) and Silicon Accelerometer (SA). Unlike conventional direct calibration methods applied at the Inertial Measurement Unit (IMU) level, the proposed method incorporates an additional indirect calibration step at the INS level, where the INS consists of an IMU, a power supply module, a navigation computer module, and a housing. The navigation computer performs self-alignment and navigation, while collecting data for the indirect calibration, which estimates inertial sensor errors using the first-order gradient of velocity error. To evaluate its effectiveness, we constructed an INS initially calibrated with the direct method, then applied the proposed indirect calibration. Navigation performance in a stationary state was compared between the direct calibration and two-step calibration. Experimental results show that the two-step indirect calibration improves navigation accuracy.