Magnetic compass is required by law, and at least once a year, or as often as it may be necessary, the deviation to be determined by turning the vessel. In this connection it is advantageous to correct the compass for deviation, as high deviation is inconvenient and may cause the compass card to wander when the course is altered, or when the vessel yaws in bad weather, or when the steering is unsteady.
The most serious factor causing the compass vesseltracker to be unsteady is heeling error. Under unfavourable circumstances – in particular on northerly or southerly courses – the fluctuations of the compass card may become so violent that it will be difficult to steer by the compass.
Even if heeling error has been partly neutralised at the start of the voyage, it may change as the vessel proceeds. If there is a great change in latitude, or northerly (southerly) courses are steered for long periods, the compass may become unsteady and it may help to adjust the heeling magnet. After the original position of the heeling magnet has been marked off, move it up or down until the compass becomes steady; next, if possible, check the deviation on the compass course and at the two adjacent cardinal points.
The deviation of the compass should be determined at least once during every watch and after each alteration of course. Deviation observations on a specific course as well as when the ship is turned should be entered in the vessel’s log.
In addition to magnetic compass the vessels are fitted with gyro compass(es).
Course Recorder
The course recorder shall show UTC and when the vessel is at sea the position, wind and weather each day at 12 o’clock noon shall be entered on the recording paper. Every arrival and departure port or anchorage, the date and location must be written on the chart.
Manoeuvring Printer
The printer for engine manoeuvres shall show UTC and shall keep the same minutes as clocks in the engine room and on the bridge.
When the vessel is at sea, this shall be checked each day at 12 o’clock noon.