ORIGINAL: BGfisher
As shown, the line of sight distance is the hypotenuse of the triangle. However, due to shooting in a downward angle you still make the shot as if it were ground level distance. If you use proper form, keeping the upper body in a "T" formation by bending at the waist there should be very little difference in POI compared to ground level.
Exactly
Gravity acts the same regardless if the arrow is shot up/down or sideways.