Originally Posted by
dmounts
When shooting uphill or downhill, Gravity must also be considered. If you've ever ranged a target from a treestand or elevated position and fired an arrow based on that distance, you'll find that the arrow hits the target high. This is gravity coming into play.
At extreme heights and ranges, this can have an effect. In other words, if the hypotenuse (slant distance) is much greater than horizontal distance. A hunter at 20 feet shooting at 30 yards shouldn't notice much difference, however. The slant distance for a hunter 20 feet up at a target 30 yards out from the base of the tree is....
30.7 yards.
Anyone shooting high under those circumstances is likely just breaking their form.
Good advice in your link, however. Especially with regards to trajectory when shoot through 'holes' in vegetation. Unless you have a really speedy bow, you're probably not shooting a perfectly linear trajectory.