COVARIANCE ANALYSIS OF STRAPDOWN INS CONSIDERING GYROCOMPASS CHARACTERISTICS

Presented in this paper is a complete error covariance analysis for strapdown inertial navigation system (SDINS). We have found that in SDINS the cross-coupling term in gyrocompass alignment errors can significantly influence the SDINS error propagation. Initial heading error has a close correlation with the east component of gyro bias error, while initial level tilt errors are closely related to accelerometer bias errors. In addition, pseudostate variables are introduced in covariance analysis for SDINS utilizing the characteristics of gyrocompass alignment errors. This approach simplifies the covariance analysis because it makes the initial error covariance matrix to a diagonal form. Thus a real implementation becomes easier. The approach is conformed by comparing the results for a simplified case with the covariance analysis obtained from the conventional SDINS error model.