Compass errors: turning error

In a turn, the compass lags turning through north and leads turning through south.

MAGNETIC COMPASS

HEADING INDICATOR (actual heading)

Cover the heading indicator (compass only) Show when to roll out

Latitude26°N

Straight and level

No turning error. The compass matches the heading indicator.

Actual 000°Compass 000°

Key points +

UNOS: Undershoot North, Overshoot South

Northern Hemisphere. Turning to a northerly heading, the compass lags: roll out before it reaches the heading (undershoot).
Turning to a southerly heading, the compass leads: roll out after it passes the heading (overshoot).
The amount is roughly your latitude in a standard-rate turn. East and west headings have almost no turning error.
Starting a turn from north, the compass briefly shows a turn in the opposite direction. Starting from south, it shows a turn in the right direction but faster than you're actually turning.