Deflection (ballistics)

Deflection shooting is a technique of shooting ahead of a moving target, also known as leading the target, so that the projectile will "intercept" and collide with the target at a predicted point. This technique is only necessary when the target will have significantly displaced its position during the time the projectile would take to reach the target, which can become the case over very long distances (e.g. a long sniper shot), due to fast moving targets (e.g. aerial dogfight against an opposing aircraft, or anti-aircraft fire against passing aircraft), or while using relatively slow projectiles (e.g. a bolt shot from a crossbow, or a basketball thrown to a running teammate). Gyro gunsights developed for aircraft of the Second World War displayed a reticle that compensated for target lead. Modern fighter aircraft have automated deflection sights, where a computer calculates lead and projects the solution onto a head-up display (HUD). The visual assistance with targeting the gun is offset by the speed and agility of modern aircraft, compared to the days when targeting was less advanced. In artillery, deflection is also used against fixed targets to compensate for windage and range. Due to the Earth's rotation, surface points have different velocities and curved motion, leading to apparent Coriolis drift of a long-range target. Modern computer games of the first-person shooter genre typically feature a number of relatively low-velocity projectile weapons such as unguided shoulder-fired missiles, or fictional projectile weapons such as "plasma guns" or "nail guns", which necessitates an attacker to lead his aim ahead of moving targets. Computer games that accurately model the ballistic trajectories (including velocity) of firearms also require leading of fire, much as in real life. This applies equally to combat aircraft (or even combat spacecraft) simulators, where the velocity of the craft involved are significant enough to require leading with projectile weapons.