And yes, there is a "trick". If you range trees around you before any deer show up, range them horizontally at the same level you are sitting and you will know the true horizontal distance, which is the distance that matters for the shot.
Great simple tip thanks! I am confused though, using the example in the guide and the pythagorean theorem a deer at 23 yards level if you were about 22 feet in a tree would be 32 yards sighting from the tree. That is a difference of about 9 yards (I rounded the decimals). What am I missing here.