Roger Lee Easton, Sr. (April 30, 1921 – May 8, 2014) was an American scientist/physicist who was the principal inventor and designer of the Global Positioning System, along with Ivan A. Getting and Bradford Parkinson. He was born in Craftsbury, Vermont.

Ivan Alexander Getting (January 18, 1912 – October 11, 2003) was an American physicist and electrical engineer, credited (along with Roger L. Easton and Bradford Parkinson) with the development of the Global Positioning System (GPS). He was the co-leader (the other being Louis Ridenour) of the research group which developed the SCR-584, an automatic microwave tracking fire-control system.

Bradford Parkinson (February 16, 1935) is an American engineer and inventor, retired United States Air Force Colonel and recalled emeritus Professor at Stanford University. He is best known as the lead architect, advocate and developer, with early contributions from Ivan Getting and Roger Easton, of the Air Force NAVSTAR program, better known as Global Positioning System.

The Global Positioning System (GPS), originally NAVSTAR GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force.

It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. Obstacles such as mountains and buildings block the relatively weak GPS signals.

History:

The GPS project was launched in the United States in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including classified engineering design studies from the 1960s. The U.S. Department of Defense developed the system, which originally used 24 satellites. It was initially developed for use by the United States military and became fully operational in 1995.

Civilian use was allowed from the 1980s. Roger L. Easton of the Naval Research Laboratory, Ivan A. Getting of The Aerospace Corporation, and Bradford Parkinson of the Applied Physics Laboratory are credited with inventing it.

The work of Gladys West is credited as instrumental in the development of computational techniques for detecting satellite positions with the precision needed for GPS.

The design of GPS is based partly on similar ground-based radio-navigation systems.

According to en.wikipedia