Many radar and ARPA sets carried onboard modern vessels have the capability for the OOW to enter 'ARPA maps' and to retrieve previously prepared maps. Although the setup varies between manufacturers, and it can often be quite fiddly to lock the overlay, such maps on the radar screen are a useful tool when monitoring the vessel's progress throughout her passage.
Unfortunately, however, once entered into the ARPA's menu these maps do NOT self correct. It is important to remember this and, when carrying out a passage plan that will make use of a previously prepared map, to properly check the content of the mapping files.
The recent changes to buoyage and TSS in the Netherlands sector of the Southern North Sea, carried out on August 1st 2013, is an good example that shows the importance of checking radar and ARPA mapping files.