It's also usefull when friends give you info and you want to check them out away from your boat.
Sometimes these are completely new marks, and at other times they are just a short distance away from known "old marks"
Look at some of the club marks that you can now access. Checking them against navionics should help you see the features.
Of course you could short cut all of this by bribing Members with venison, or taking up offers of trips on other boats.
Charlie