Initial Attitude Estimation of Tactical Grade Inertial Measurement Unit for Airborne Environmental Camera

The initial attitude estimation of the airborne navigation system greatly affects the overall attitude accuracy. The initial alignment depends on the inertial measurement unit’s performance. In the case of the tactical grade inertial measurement unit, even though tilt angles can be estimated relatively accurately by using accelerometer outputs, it is difficult to determine the azimuth angle with gyroscope outputs because of the uncompensated bias components. Therefore it is necessary to use the appropriate calibration method in order to compensate biases. In this paper, we propose a new method to determine the uncompensated biases. Furthermore, the measurement error covariance is difficult to determine in the navigation error equation because of the navigation frame disturbance. This paper proposed to use the adaptive filtering method to calculate the measurement error covariance matrix. Simulation and laboratory experiments were performed to show the effectiveness of the proposed method of determining uncompensated bias and the adaptive filtering method of calculating the measurement error covariance.