When hunting in bushveld area, even using some curved trajectory rifles like a muzzle loader, I never needed one. Then I moved to the FreeState = grassveld = long shots. A client 'donated' his Bushnell YardagePro. It works great to measure the distance to a shed to 600 or more yards. However a springbuck is just to 'small' at 300 yards to get a reading from.
Now, thanks to another American client, I have a Nikkon ProStaff 550. This works well on springbuck up to well beyond the 400 yards or so that I'm prepared to take a shot at.
I don't know the term, but the 'target area' for a reliable reading is critical if using one in very open area for long shots. For bow&arrow ranging ist seems anything will work. For shots beyond abot 200 yards on smaller animals you need a higer specification range finder in the 'target area' at distance. It helps me very little to know that I'm exactly 746 yards from a 10yards wide 3yards high solid white-walled shed. I need to know how much beyond 300 meters a springbuck is.
In good hunting.
Andrew McLaren