Pursuit guidance is a form of guidance widely used in older ground attack missiles.
In pursuit guidance, the missile is steered so that the velocity vector of the missile always points at the target. In the early days of guided missiles where the computers were analog this was an easy implementation in the hardware. It found particular use in the early laser-guided bombs with the aerodynamically stabilized birdies on the front of the bomb. The birdies sit on a universal joint and thus will point in the direction of the relative wind. If the laser receiver is placed on this wind stabilized reference, the angle that the laser is off the wind vector is the same as is measured relative to the centerline of the seeker. Thus, the angle is constructed easily in analog hardware.