Abstract: Apparatus and method for determining the trajectory of a supersonic projectile of unknown velocity and direction having at least three spaced-apart sensors capable of encountering a shock wave generated by a supersonic projectile passing in the vicinity of the sensors and capable of generating signals in response to the shock wave, which signals are related to an azimuth and elevation angle of a unit sighting vector from each sensor to an origin of the shock wave. Means are provided for calculating from the signals the azimuth and elevation angle of the unit sighting vector from each sensor to the origin of the shock wave. Means are provided for calculating from the unit sighting vector of each of the three sensors, the azimuth and elevation angle of the local trajectory of the projectile.