Abstract: A system for locating forward observation posts with respect to a base ston. A continuous electromagnetic wave with frequency f.sub.o is transmitted from an artillery projectile or missile in flight. In addition, a relative time code is transmitted on the same or a separate carrier frequency either from the projectile or from a ground station. The frequency f.sub.o of the electromagnetic wave from the projectile or missile is doppler shifted above or below its basic frequency due to the velocity of the projectile. This doppler signal f.sub.d always goes through its basic frequency f.sub.o or zero doppler at a point which is representative of and identifies an observer's position in the horizontal or subtrack direction of the projectile. This occurs regardless of the observer's distance away from the subtrack. Thus, all observers on a given perpendicular to the subtrack observe f.sub.o or zero doppler at the same time. To locate a specific observer, two projectiles or missiles must be fired.