ORIGINAL: Grandviewer
It's the horizontal distance from the base of the tree to your target spot on the deer. That reading from 20 ft up a tree will be off from thehorizontal distance. Forinstance, a 20 yard reading up a tree will be more like 16 or 18 yards when on the ground.
I don't like it when misinformation is posted and I know it wasn't intentional, and don't take this the wrong way but that is a major difference. 20' up and laser ranging a deer reading 20 yards, that animal will be 19 yards away, the difference is rarely ever over 2 yards, not 4 yards, that's huge when it comes to bow trajectory.
There is rarely ever more than 2 yards difference in bow ranges. Bend at the waist an aim for the exit hole.