Keely Grasser, author of “From Duct Tape to Drones: Military Inventions That Impact our World,” in the Winter 2015 edition of Phoenix Patriot Magazine, interviewed Richard Easton and Eric Frazier for background information on GPS, one of eight innovations covered in the article. The key point she makes: GPS technology has spread throughout so many military, commercial and consumer industries that economists now find it impossible to accurately put a dollar figure on its overall worldwide impact.