GPS is the best friend we’ve got, but we all know that it suffers from the ‘rubbish in – garbage out’ problem. Every time a waypoint is plotted on a paper chart and you’re at home on your berth, you can confirm you didn’t screw up by hitting ‘GoTo’. Read off the range and bearing, then plot it. Does it tally with where you absolutely know you are? If not, take a good look at those lat/long co-ordinates!