磁罗经校正
magnetic compass adjustment
磁罗经指向误差
directive error of magnetic compass
磁罗经装设
magnetic compass installation
电磁自差
electromagnetic deviation
海军传送磁罗经
admiralty transmitting magnetic compass
陀螺稳定磁罗经
gyrostabilized magnetic compass
天测罗经差
compass error by celestial observation