Michael, I almost posted the same thing. However, judging using a reticle (especially out away from suburbia) is not something that is super simple. It requires a bunch of practice to get good enough to use for high percentage one shot hits on animals. If I was out and needed to make a shot on an animal at long range (600yds +) without my range finder, I'd make a guess and take a shot on the hillside to verify my range. I'd then mark my shot with my reticle and use my first impact and aimpoint to determine the correction needed. In this case, the angle has no use, except for the first shot.
AJ