Today, GPS is engrained in our lives, from figuring out the best route home after a road closure to making sure a loved one reached their destination safely. The modern system, which now consists of 31 satellites orbiting the earth, five ground control stations located around the globe, and many receivers which are found in our phones, cars, etc., began as a project under the Department of Defense in 1973. The work was carried out across several federally funded institutions: the US Naval Research Laboratory, The Johns Hopkins University Applied Physics Laboratory, and The Aerospace Corporation. Fully operational in 1993, the full capabilities of the system became freely accessible across the globe for peaceful purposes in 2000.
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