What is "line-of-sight"

Line-of-sight or line of sight may refer to:

• Line-of-sight (missile), the straight line between the missile and the target
• Line-of-sight propagation, electro-magnetic waves travelling in a straight line
• Line of sight (gaming), visibility on a gaming field, i.e. who can see what
• Direct fire or line-of-sight fire, shooting directly at a visible target on a relatively flat trajectory
• Radial velocity or line-of-sight velocity, an object's speed straight towards or away from an observer
• Sightline, an unobstructed line-of-sight between a subject and object
• Leonardo da Vinci's term for a structure within the human eye, according to eye movement in reading

In missile guidance, Line of sight is the straight line between the missile and the target. At the end of the engagement the distance will be zero. See Command guidance#Command to Line-Of-Sight (CLOS).

By Pursuit guidance the missile is steered so that the velocity vector of the missile always points at the target, i.e. has the direction of the Line of sight.