Abstract: A tracking system including: a plurality of acoustic sensors rigidly held apart from each other and from an acoustically reflective surface; a processor configured to: receive spatial relationships between the plurality of acoustic sensors and between the plurality of acoustic sensors and the acoustically reflective surface; receive a plurality of measurement signals; identify: in the plurality of measurement signals, timing of arrival of a supersonic shockwave of a projectile to the respective sensor; and timing of arrival of a reflection of the supersonic shockwave from the acoustically reflective surface to the respective sensor; determine at least a portion of a trajectory of the projectile, using: the timing of arrival of the supersonic shockwave; the timing of arrival of the reflection; the spatial relationship between the plurality of acoustic sensors; and the spatial relationship between sensors and the spatial relationship between sensors and the acoustically reflective surface.