PaulTon:So where is OB?
OB is where it is on the actual course; OB may coincide with the hole map's edge, but it can also be somewhere 'off the map' (as indicated in your pic) ... or for other holes/courses the OB line may be well inside of the edge of the hole map.
A good example is St Andy's Road Hole (#17). On your approach shot, if it lands a bit long and left of the infamous green-side bunker, will find OB well before it goes 'off-map!
You've been warned, lol.