no your right. I was actually just figuring this out last night with a couple of friends and 18 feet up a tree considering the ground is at a 90 degree ang;e below you the distances are only of by less than a yard. I guess these range finders would be good for extreme angles but I see them as pretty much useless for the common bowhunter.

I as you range find distances on the ground when I set up my stand.

 

I have a Leapold and I would have to agree. Once your bow is shooting over 250 FPS for bowhunting, they are pretty useless. Now, I also shoot rifles. They are very effective for rifle shooting.

 

Using an OptiLogic rangefinder on the Darrington Washington course I found that my cuts from my cut chart and inclinometer varied by more than a couple yards on a few targets on the really long targets. I will continue to use the tape on cut chart on my lower limb and an inclinometer for hunting in very mountainous terrain.

 

another way

Besides ranging from the ground to the base of your tree, you can range other trees at deerstand level from your stand.

 

They do work. If you are shooting at a deer that is 40 yards away but is on a 30 degree incline (or decline) then you would actually shoot like he is at 35 yards. Maybe for you folks that shoot 400FPS and never take a shot over 20 yards it doesn't matter, but shooting 40+ yards in the mountains will make a difference.

 

In that example...

Deer at 40 yards away.
You are shootind down a 30 degree slope

You would have to be 69'-3 3/8'" above the deer in that example.

Now I don't know how many of you shoot deer 40 yards away while nearly 70 foot up a tree....but I'm guessing it's far and few between. Even in the mountains 30 degrees would knock your socks off to look down at something that close to it. At that down angle I'd be more concerned with the narrowness of the body rather than the difference in the shot. It may be "possible" to shoot down at 30 degrees....but I suggest someone who thinks it's plausible to get out an incinometer and measure down 30 degrees on their bow as they hold it and see how hard it would be to even bend and shoot like that. To shoot off the side of the mountain like that would require shooting with one hand because the other hand would be holding you to the mountain.

Now here in the real world here's another example.

Deer at 40 yards away.
Hunter 20 foot up a tree.

The on the ground distance is obviously 40 yards (120 feet)
The distance the arrow will travel is 121' - 7 7/8"

So a difference of less than 2 feet or less than a yard. The angle would be 9.46 degrees.