Editing Sputnik 1 (section)

=== Satellite navigation ===
{{main|Satellite navigation|Global Positioning System}}
The launch of Sputnik also planted the seeds for the development of modern satellite navigation. Two American physicists, William Guier and George Weiffenbach, at Johns Hopkins University's [[Applied Physics Laboratory]] (APL) decided to monitor Sputnik's radio transmissions<ref name="guier-weiffenbach">{{cite journal|last1=Guier|first1=William H.|last2=Weiffenbach|first2=George C.|title=Genesis of Satellite Navigation|journal=Johns Hopkins APL Technical Digest|volume=19|issue=1|pages=178–181|year=1997|url=http://www.jhuapl.edu/techdigest/td/td1901/guier.pdf|access-date=April 9, 2012|archive-url=https://web.archive.org/web/20120512002742/http://www.jhuapl.edu/techdigest/td/td1901/guier.pdf|archive-date=May 12, 2012|url-status=dead}}</ref> and within hours realized that, because of the [[Doppler effect]], they could pinpoint where the satellite was along its orbit. The Director of the APL gave them access to their [[UNIVAC I|UNIVAC]] computer to do the then heavy calculations required.

Early the next year, Frank McClure, the deputy director of the APL, asked Guier and Weiffenbach to investigate the inverse problem: pinpointing the user's location, given the satellite's. At the time, the Navy was developing the submarine-launched [[UGM-27 Polaris|Polaris]] missile, which required them to know the submarine's location. This led them and APL to develop the [[Transit (satellite)|TRANSIT]] system,<ref>{{cite book|title=Where good ideas come from, the natural history of innovation|author=Steven Johnson|publisher=Riverhead Books|place=New York|year=2010}}</ref> a forerunner of modern [[Global Positioning System]] (GPS) satellites.