Further to the advice given on radar and the instructions given in the appropriate
operating manual, the following points are to be checked when using ARPA:
That performance of the radar associated with the ARPA is at its optimum.
In addition the ARPA may be fitted with a test programmer of marinetraffic.
That heading and speed inputs to the ARPA are satisfactory. Serious errors of output data can arise if heading and speed inputs are incorrect. When using a ground stabilised mode of ARPA display, particularly in areas where significant current and/or tidal streams exist, care should be taken when interpreting the information on the movement of other vessels.
i) Audible alarm active/inactive.
ii) Automatic acquisition mode active/inactive.
The above warning devices do not relieve the user of the duty to maintain a proper look- out by all available means. It shall be borne in mind that small targets may not be picked up by the automatic acquisition system.
All navigating officers shall fully familiarize themselves with the particular characteristics of the vessels ARPA as soon as possible after joining vessel. As with the radar, clear weather practice is important in order to gain and maintain a familiarity with the various functions of the ARPA, and the output provided compared with the actual situation.
GPS
This instrument is a very powerful aid to navigation with great accuracy and stability. However, it can periodically lose contact with one or more satellites and will in such cases calculate dead reckoning and the position will not reflect the normal accuracy.
Echo Sounder
This instrument shall be used whenever the vessel is navigated in waters where the depths are such as to render it useable and where the safe navigation of the vessel requires it to be utilised. Where the vessel carries depth recorder with alarm, this instrument shall be used when navigating in narrow waters and in all other circumstances where the depth of water makes it a useful aid which may increase the safe navigation of the vessel.
