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I have a chart plotter on board so no problem for me but on my android phone (old galaxy ace) I have a free app called MMtracker which will use the memorymap os 1:25,000 broads map to show my location as well as being able to show speed and position in various formats, the mapping came from a one eyed chap with a wooden leg from the coast of somalia, had a lovely parrot too....
LM: Sounds very much like the guy I got my OS maps from! I use mine with Alpine Quest but once I have some more suitable maps or aerial photos I may well switch over to Androzic.
Try this free app. Mad Mutt Marine. Put together by an amateur sailor on the South Coast. Gives you all the data you might reasonably need. Works on proper boats too!