Investigation of the so-called Magnetic North Immeasurable Area in the South Sea of Korea by a newly assembled three axis Magnetometer

Abstract

An area exists on the South Sea of Korea where the magnetic compass is said to turn round and round not giving a fixed direction to the navigator.We newly assembled a three axis magnetometer system composed of a three axis fluxgate magnetometer, a GNSS compass, a two axis clinometer, and a multi-channel data logger, to investigate if there really exists such an area.We supposed that the horizontal component of the vectorially measured magnetic field on such an area will be too small to maintain the magnetic compass’s needle to one fixed direction. We processed the measured data mainly through two steps. Firstly we transformed the random coordinate system into a fixed coordinate system, i. e., into the geographical coordinate system. Secondly we performed an inversion to eliminate the effect of the ship itself from the measured data.On the finally achieved anomaly map we could not find such an area where the horizontal component is so small that it could not maintain the magnetic compass’s needle to a fixed direction.We conclude that such statement about the existence of the so-called magnetic north immeasurable area on the South Sea of Korea does not have a strict scientific base.