Simrad IS20 Manual page 63

Compass calibration
Before the compass calibration is started, make sure that
there is enough open water around the vessel to make a
full turn.
The calibration should be done in calm sea conditions and
with minimal wind to obtain good results. Use about 60-
90 seconds to make a full circle.
1. Highlight the Calibrate line in the dialog
2. Begin turning the boat to port or starboard
3. Press the Menu/Enter key to start the automatic
compass calibration
− An information window will be
displayed when the calibration
procedure is running.
− The digits below the bargraph
will read 0.0 when the turn
rate is correct. Too high or too
low speed is indicated as
follows:
Configuration | 63