Operational principle of gyrocompasses

Good afternoon,

Can somebody explain - in simple terms - the operation of a gyrocompass?


A gyrocompass is a special type of compass used on ships (and also airplanes) to find true north, which is slightly different from magnetic north that a normal compass points towards.

Imagine a spinning top. When you spin it, it tries to keep pointing in the same direction, even if you move the surface it’s on. This is called “gyroscopic inertia”.

Now, combine that spinning top with the fact that Earth is also spinning. The gyrocompass uses the force of the Earth’s rotation to align itself with true north.

To start, the gyrocompass is set spinning. It doesn’t know where true north is yet, so it’s just spinning in whatever direction it was started in. But, because of the way the Earth is spinning, the gyrocompass gets gently nudged over time. Little by little, these nudges push the spinning compass until it lines up with the Earth’s spin. And that direction is true north.

Once it’s aligned with true north, the gyrocompass keeps spinning and holds that direction, just like the spinning top. So even if the ship turns or rocks, the gyrocompass keeps pointing towards true north. This allows the ship’s navigator to always know which direction the ship is heading in.