Leonardo da Vinci designed and studied compass mechanisms for finding direction at sea.
A magnetic compass uses a magnetized needle that aligns approximately with Earth’s magnetic field. This gives navigators a reference direction even when landmarks are hidden by darkness, fog, or open ocean.
The compass was not invented by Leonardo; magnetic compasses were known in Europe before his lifetime and had much older roots in China. Leonardo’s notebooks include investigations of magnetic behavior and practical instruments, showing his interest in navigation and natural forces.
A compass is not the same as an astrolabe or sextant. Those instruments help determine position from the sky, while a compass primarily indicates direction.