Abstract
Buildings that contain magnetic bodies (e.g., steel frameworks and reinforcing steel bars) reduce the homogeneity of the Earth's magnetic field. Such magnetic disturbance interferes with compass swinging sites and magnetic testing site. Keeping the disturbance sources away from the site enough, or using non-magnetic materials for buildings is the best solution of such a problem, however, we have to prepare a huge ground for the site, or accept very expensive construction cost of the buildings. Moreover, the magnetic shielding is useless for the disturbance of the magnetic declination. This paper proposes a method for reducing the disturbance of the magnetic declination by using ferromagnetic materials as a magnetic compensator. The procedures of the proposed method are as follows: measuring the distribution of the declination of an infected site; simulating or measuring effects of the compensators; designing a number and arrangement of the compensators by comparing the distribution of the declination on the site with that of the compensators. It is shown that the proposed method recovers the homogeneity of the site with a diameter of 30 m by about 30% by setting two compensators appropriately.
