Calling the shots is what the Gunner's Mate does (did) so that the gun or battery (be it ship borne or land based) could eventually hit its target. The impact point of each round was relayed back to the Gunnery Officer, changes were made to the inclination and/or azimuth (direction) of the gun/s - and whammo.

It was originally used for land based battles, with the observations made on the high ground and signalled back to the gun/s. Subsequently adapted for sea battles, +/- air or satellite support to call the shots. Nowadays controlled by radar, laser and/or video. Often wire guided as well.

stales