Extended dipole approximation of a ship induced magnetic signature modeled by means of a hollow cylinder

In this paper a novel analytical model to determine the induced magnetic signature of a ship supposed stationary is presented. The analytical model is based on the extended dipole approach which was applied until now to submarines according to which the ship is regarded as a magnetic dipole of finite length. This new approach enables a comparison with measurements of the magnetic signature based on magnetometers. The ship is modeled by means of a hollow circular cylinder and the induced magnetic signature is analytically calculated according to the extended dipole approximation and, in the outer region, is compared to the one obtained by means of the point dipole approximation which fails at short distances. It is proved, both analytically and numerically that, in shallow water, there are differences in the induced magnetic signature at fixed depth which are attributed to the local earth’s magnetic field depending on the geographic location. These results would be beneficial for identifying and detecting with reasonable accuracy a ship in terms of its magnetic response.