A pole is obstructed if you cannot pass a 30"X 30" (imaginary) box from the ground to the top of the pole without it touching anything except any one point on the wood. It does not have to be straight up (but it is preferred), you can have a 90 degree change in climbing space as long as there is 4' of clearance before the next 90 degree turn.
This is CABL.com posting #226839. Tiny Link: cabl.co/m7aR