Application of aided inertial navigation system to synthetic aperture sonar micronavigation

Abstract

In order to improve short-term navigational accuracy, critical to successful SAS processing, a highquality Inertial Navigation System (INS) is investigated, which consists of an inertial measurement unit (IMU) and a strapdown navigator. Although the strapdown INS recently acquired at SACLANTCEN is one of the best available, the accuracy of positioning remains insufficient, in particular for highfrequency SAS. The INS performance was predicted via psi-angle error analysis of the navigation equations and a navigational simulator/estimator provided by NDRE (Norwegian Defence Research Establishment). The short-term residual errors of position and attitude displacement were analyzed in terms of dominant measurement error components and their sources. Preliminary results show that

the attitude error is negligible due to the low value of gyro bias and white noise. The position

displacement error is dominated by a quadratic drift due to accelerometer bias. Integrating the INS with additional navigation sensors (e.g., Doppler Velocity Log, depth meter, etc.) and SAS motion compensation techniques by means of an appropriate fusion architecture will significantly reduce the most critical error components. The design, development and test of the combined SAS-INS architecture will be the main objective of future work.