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 accurate 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 uses the adaptive Kalman filter method to calculate the measurement error covariance matrix.