The Problem Suppose after you've climbed 30 feet into a tree stand, a buck shows up, sidehilling a steep downhill slope. A standard-model rangefinder will tell you that the actual distance to the buck is 30 yards. But gravity only influences an arrow's trajectory over the horizontal distance, which is much shorter. If you hold dead on with your 30-yard pin, you'll miss high. But even if you know better, how are you going to figure out the horizontal distance from your stand?