Simrad AP26, AP27 manual Local magnetic and heading errors

Maintenance

4.When the calibration is completed, (after having made approximately 1 1/4 turns), it will be confirmed by the display reading “Confirmed”.

Compass deviation

The heading from a magnetic heading sensor will normally have a deviation when compared with the actual direction of the earth’s magnetic field. This is caused by interference from the boat’s local magnetic field. The deviation will be at a minimum if the compass is placed as far as possible from any magnetic object on board. On the other hand, you may have to compromise with other requirements for the installation of the compass (page 65).

During the calibration, the compass will measure the magnitude and direction of the local magnetic field from where the compass is mounted. The magnitude is given in % of the magnitude of the earth’s magnetic field. If the local magnetic field is stronger than the earth’s magnetic field (the local field is reading more than 100%), the compass calibration will fail. If the local field is reading more than 30%, you should look for any interfering magnetic objects and remove them, or you should move the compass to a different location. The local field angle will aid you to the local interfering magnetic object. See drawing.

Lubber line Lubber line

Note ! In certain areas and at high latitudes interference becomes more significant exceeding ±3° may have to be accepted.

Magnitude of local field in % of earth’s magnetic field.

Direction of local field with respect to lubber line. It can also be on the reciprocal.

the local magnetic and heading errors

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