Strapdown three-axis magnetometer is widely used to determine the heading angle of a vehicle to which it is attached. Unfortunately, the outputs of three-axis magnetometer are often distorted by various magnetic field sources. Therefore, a calibration procedure must be performed before it is used. This paper presents a new calibration algorithm to determine calibration parameters based on a constrained total least-squares (CTLS) technique. A Newton iteration method is utilized to determine the CTLS solution. Unlike existing calibration algorithms, the proposed algorithm yields efficient estimates without assuming a priori knowledge of the noise distribution. Thus, it is easily implemented and suitable for practical applications. The results of simulations and experiments reveal the superiority of the proposed algorithm to the compared algorithms.

This letter reports an experimental evaluation of a three-axis magnetometer into an inertial navigation system (INS) for underwater localization. The magnetometer measurements of geomagnetic field are compared with map values to provide position updates to the INS. The concept of such navigation system is not new but lacks test verification and actual application. We examine the capabilities of the integrated navigation by using a localization algorithm based on the interval knowledge of geomagnetic field values. The underwater experimental result indicates that the use of geomagnetic values significantly reduces the growth of position errors of an INS.

We have developed an attitude-independent calibration method for a shipboard magnetometer to estimate the absolute strength of the geomagnetic field