Owlbait, that is the correct way to figure the distance. However extrema12 and myself were simply telling you how to determine the rough distance "in the field" when an animal is coming thru. You could either get one of the new range finders, or measure every tree in your area and have your daughter do the math if you need the exact distance. My point is, in all my years of shooting at deer, leaves, whatever from my stand, if the object is 15yds from the base of my tree I aim as if its 15yds. If its 16 or 17yds from me to the object, my accuracy has never been good enough to tell the difference. I suspect you will find the same thing. Good luck, season is right around the corner. 8^)