In the days before the satellite-based Global Positioning System (GPS), scientists used instruments like the cinetheodolite to track a missile’s flight. A cinetheodolite is the combination of a surveying instrument called a theodolite and a motion picture camera. The earliest cinetheodolites used relatively low speed cameras (five frames per second) but later models had much faster frame rates. A theodolite is a rotating optical instrument that uses elevation and bearing (“azimuth”) to pinpoint the line of sight to a distant object based on the known location of the instrument itself. The cinetheodolite generated a record of the horizontal and vertical angles from the instrument to the missile on each film frame, creating a continuous record of the line of sight to the missile through its flight. Cinetheodolites located across the length of the range were used in groups of three from shortly after launch to impact. A centralized clock managed the time stamp that was imprinted on every frame on every instrument across the range, tying data from all instruments together to specific moments in time.  By combining lines of sight from multiple instruments, researchers could triangulate the missile’s position to within a half-meter (19 inches).