noun
magnetic compass
A compass that uses a magnetized needle to indicate magnetic north. Common in navigation and surveying contexts.
登山のときは磁気コンパスを持っていく。
I take a magnetic compass when mountain climbing.
方位磁石 is a more common, everyday term for a magnetic compass, while 磁気コンパス is a technical term often used in navigation and surveying.
Compound of 磁気 (magnetism) and コンパス (compass), a direct calque from English 'magnetic compass'.