GPS has revolutionized navigation. Richard Easton is the co-author of GPS Declassified: From Smart Bombs to Smartphones, the first general book length treatment of its development.

The development and deployment of accurate clocks aboard GPS satellites is a modern analogue to John Harrison’s work on the marine chronometer during the Longitude competition of the 18th Century. John Harrison solved the longitude problem by building an accurate clock that essentially synchronized time between the departure port and the ship's current position. Circa June 1, 1964, Roger Easton from the Naval Research Laboratory discussed the accuracy of the Hydrogen Maser with Dr. Arnold Shostak from the Office of Naval Research. They agreed that it made range measurement using accurate clocks in satellites feasible, and soon after Easton started work on TIMATION, the main predecessor system to GPS. The atomic clocks used in GPS are about 10^6 more accurate than Harrison’s clock. GPS provides world-wide clock synchronization to everyone who can detect its radio waves.

Winning acceptance of a novel concept often requires a bridge between current techniques and the new approach. US Navy navigators in 1965 used celestial navigation which measures a star’s angle above the horizon. An important analog that sold TIMATION was the celestial transformation. Instead of determining the star’s angle, the navigator measured the time a signal from a TIMATION satellite took to arrive at a receiver. This talk will discuss these and other developments between 1770 and 1973 which led to the initial selection of GPS’s characteristics.

Richard Easton has degrees from Brown University and the University of Chicago. He works as an actuary in Chicago. He has been interested in space history for many years and have written several articles on the history of the invention of GPS including "Who invented the Global Positioning System?" in the Space Review, May 22, 2006 and "Timation and the Invention of the Global Positioning System: 1964-1973" in Vol 14, No 3 of Quest: The History of Spaceflight Quarterly.