Navigation and Seamanship

2.1.8.Limitations of the Magnetic Compass

The following characteristics of the magnetic compass limit its direction-finding ability:

a) Sensitive to any magnetic disturbance.

b) Useless at the magnetic poles and is sluggish and unreliable in areas near the poles.

c) Deviation (explained later) changes as a ship’s magnetic properties change. The magnetic properties also change with changes in the ship’s structure or magnetic cargo.

d) Deviation changes with heading. The ship as well as the earth may be considered as a magnet. The effect of the ship’s magnetism upon the compass changes with the heading.

e) Does not point to true north.

Care and maintenance:

a) The doors giving access to the connector magnets should always be kept locked and the key kept in safe custody.

b) The wooden part of the binnacle should be varnished not pointed, as paint may cause the doors to jam.

c) The safe iron spheres and their brackets should be painted. This prevents rust.

d) The brass part of the binnacle should be polished regularly.

e) All magnetic materials such as aerials, stays electrical machinery, dectric wires etc should be kept well away from the compass.

f) The binnacle light should be switched off during day time.