Uphill & Downhill Shots and How to Adjust
There is often confusion when it comes to shooting uphill and downhill shots on how to adjust for the incline. Do you hold high on uphill shots or low on downhill shots? Vice versa? Or no change at all? The answer may surprise some people.
The key to understanding an arrow’s trajectory on uphill and downhill shots is realizing that gravity only acts perpendicular to the earth’s surface. Thus an arrow is only acted on by gravity for the distance that it travels parallel to the earth, or rather only the horizontal distance. This results in having to aim low for both downhill and uphill shots!
Because the actual distance to the target will always be greater than (or equal to) the horizontal distance to the target, an adjustment must be made when shooting at extreme angles so that the yardage used on the bow sight matches the horizontal distance. By remembering our geometry lessons, we can quickly calculate the amount of yardage that must be “cut” for either an uphill or downhill shot.
A right triangle is formed by the shooter’s height above the target, the actual distance to the target and the horizontal distance to the target. The Pythagorean theorem states that the sum of the squares of the sides of a right triangle is equal to the square of the hypotenuse. By knowing the height the shooter is above the target and the actual distance to the target, the horizontal or the aiming distance can be calculated.
Rather than trying to do the calculations in your head or by hand, the following chart can be used to find the exact yardages:
You may notice that there is not a lot of difference in most cases; only when the height above the target is extreme or approaching that of the horizontal distance does cutting yardage become an issue. However, the difference is there and can affect the impact site of an arrow, especially when shooting at the 12 ring on a 3D target or the vitals of a animal.
Edited from original post at ArcheryPost.com