Which program was the precursor to GPS?

The correct answer is the Transit program. Transit was developed by the United States Navy in the early 1960s and became the first satellite-based navigation system to provide reliable location data for maritime and aerospace applications. It was primarily designed for submarine navigation and utilized a constellation of satellites to allow ships and submarines to determine their position with greater accuracy than terrestrial navigation methods of the time.

Transit worked by leveraging a form of time-based triangulation, where the position of the satellite and the timing of received signals would help the user calculate their geographic position. This concept laid foundational principles for further development in satellite navigation systems, ultimately leading to the creation of the Global Positioning System (GPS).

Other options in the question represent different projects or systems. For example, TRANSCAN focused on the transmission of navigational data but did not evolve into a global navigational solution like Transit. TIMATION was an experimental system that tested atomic clock technology for navigation but was more of a precursor in a technological sense rather than a fully operational navigation system. Salyut, on the other hand, was a series of Soviet space stations and not related to navigation systems. Thus, Transit stands out as the most directly relevant precursor to GPS.