Considering that the localization accuracy of the traditional magnetic gradient tensor method is easily affected by the swaying of the moving carrier platform

we propose an improved localization method based on the eigenvalue invariant of the magnetic gradient tensor. The proposed method can overcome the effects on the location accuracy caused by the swaying of the carrier platform

and the factors which would affect the localization performance are analyzed as well. Compared with the third-order tensor localization method and the multi-point linear localization method

the cost of the proposed method is that a rising or diving action of the AUV (Autonomous Underwater Vehicle) platform is needed. The simulation results show that the localization accuracy of the proposed method is close to that of Euler localization method when no environmental magnetic interference and no swaying of the platform exist.However

the localization performance of Euler method would deteriorate rapidly when some environmental magnetic interference exists. Compared with the third-order tensor localization algorithm and the multi-point linear localization algorithm

the performance of the proposed method is better

regardless of the magnetic interference or the swaying magnitude. The maximum localization error of the proposed method is no more than 15m

despite the swaying of the moving platform is increased to 10°.