Acoustic hit indicator

An improved acoustic target is considered. Acoustic targets estimate the hit coordinates of a supersonic projectile using the time of arrival (TOA) of the supersonic shock wave at several acoustic transducers located in the vicinity of the target. An improved target allows oblique hits, likely in firing practices involving roaming infantry and armor. Four trajectory parameters are estimated: two hit coordinates (x,h) on a virtual, vertical, target plane; horizontal angle of incidence; projectile velocity. Explicit expressions are provided of the expected TOA measurements and their derivatives with respect to the estimated parameters. The expressions simplify a least-squares iterative algorithm and accelerate its convergence. Expected error contour maps are provided.