Modern combat aircraft are equipped to calculate the PIP for onboard weapons at any given time. Variables that are included in the calculation are aircraft velocity, target velocity, target elevation, distance to target, forces on the projectile (drag, gravity), and others. Using the PIP marker, pilots can achieve good accuracy at ranges of up to several kilometers, whether the target is ground-based or airborne.
"Red dot" optical firearm sights like the M68 Aimpoint are another example of devices that show the PIP. Such sights project a glowing red dot between their lenses. Like on a HUD, the dot always appears over the weapon's impact point, regardless of the position of the shooter's eye. Red dot sights do not use internal computers and must be manually zeroed for maximum accuracy.