I believe that for practical purposes the yardage to targetfrom 20' up in a tree will not vary from that on the ground by more than 1 or2 ydsAFTER the distance to the target exceeds 10 yds and will increasingly diminish.

Still, physics demands that an arrow shot at an angle toward the ground will fly faster and therefore shoot higher than over flat ground. How much higher depends on the speed of your bow in the first place (the faster, the less variance).

Now, all this may be"academic" in the real world butit would be interesting to see the actual physics formula.Me, I just aim slightly lower while in a tree if the deer is close. The variance in "arrow height on target"will diminish the further away from the target you are, I believe.

Bendingcorrectly is the actual key I believe.