Magnetic Compass

 If  the observations for a magnetic compass  on a vessel show a deviation of the  compass on any heading of more than 5  degrees, the compass must be adjusted by  a qualified compass adjuster or the master  of the vessel to correct the deviation.  

 Annex G of ISO 25862:2009 also  recommends that a compass should be  adjusted when: 

1. they are first installed;

 2. they become unreliable; 

3. repairs or structural alterations have  been made to the vessel that could  affect its permanent or induced  magnetism;

 4. electrical or magnetic equipment close  to the compass is added, removed or  altered; 

 5. they show any physical defects;  

6. if a record of compass deviations has  not been maintained, or the recorded  deviations are excessive; or

 7. deemed necessary by the master for  the safety of navigation, and no less  often than every two years; every dry  docking or after significant structural  work. 

 Magnetism of a new ship can be particularly  unstable. Therefore, the performance of a  magnetic compass should be monitored  carefully during the early life of the ship, and  adjustments made if necessary. 

 To ensure a compass is in good working  condition, it is important to check  performance of magnetic compasses  particularly after: 

1. carrying cargoes which have magnetic  properties; 

2. using electromagnetic lifting appliances  to load or discharge cargo;

 3. a vessel has been in a casualty where  it has been subject to severe contact or  electrical charges;  

4. a vessel has been operating on short  voyages for a long period of time then  relocates, which results in a large  change in magnetic latitude; or

 5. a vessel has been laid up or has been  lying idle. Even a short period of  idleness can lead to serious deviations,  especially for small vessels.

 Portable electrical equipment, for example  radios, tape recorders and mobile  telephones or items made of steel, may  affect the performance of a magnetic  compass. Care must be taken to ensure that  such items are kept well away from the compass position.