Hurmph... You should have 2 systems on board that will never lie to you and give accurate readings, the radar and depth sounder. Get the dividers and parallel ruler out for a pinpoint location. IMO. GPS is the best invention since caned beans but I feel that the new generation is becoming too dependent and a little "Old School" navigation class is the best back-up. Oh, and by the way USCG regs require a paper chart to be on board so be ready to print those charts from your PC if you've already tossed your hard copies out.