Command guidance receives its name from the fact that guidance commands are generated by a guidance processor that is not a part of the missile. For a surface-to-air system these commands usually are determined by a guidance processor located at the missile launch point and transmitted to the missile.

The measurement system consists of a target-track and missile-track radar located at the launch point as shown in Figure 2. Measured position data for the target and missile are fed into a computer also located on the ground.

The computer calculates the guidance commands, and they are transmitted to the missile where they are carried out by the autopilot and control system of the missile.

Command to Line-of-sight: one way to implement guidance with a single ground-based sensor is to track the target and keep the missile within the target-track beam, Slight movement of the missile away from the center of the beam is sensed by the ground-based sensor, and correction commands are transmitted to the missile to bring it back to the center of the beam, this is called command-to-line-of-sight guidance.

In a different implementation that cannot be classified as command guidance, the missile itself senses its position within the beam and develops its own guidance commands, this is called beam-rider guidance.

Track via Missile: more accurate guidance than command guidance is possible by placing a sensor on the missile so that as the missile approaches the target, the error produced by the inherent angular tracking inaccuracy is diminished by the shortened range from the missile to the target. In addition, the position of the target is directly measured relative to the missile.

This eliminates the error that would have been produced by a ground sensor that estimates both the missile position and the target position and calculates the difference. If the measurements made by the onboard sensor are transmitted to a guidance processor on the ground, the system is called a track-via-missile (TVM) guidance system.