Why The US Military Made GPS Free-To-Use

Real Engineering goes into the history of the US GPS system.
MilkmanDansays...

Interesting and good, but it missed an opportunity to talk about another reason that Clinton removed the scrambling that reduced accuracy to ~100m in 2000:

It was fairly easily circumvented.

Your GPS device isn't sending anything TO the satellites -- just receiving FROM them. So, the scrambling had to be done on a system-wide scale; it couldn't skew your location 37m to the west and your friend a block away 62m northeast. So, every device in a particular area (that can see the same satellites) would be skewed by essentially the same distance and direction.

That means that all you needed to circumvent the scrambling was a GPS device relatively nearby at a known latitude and longitude. Then you took the GPS reported coordinates of that device and compared them to the known coordinates, and badda-bing you've got the skew figured out.

I remember that system being used to overcome the scrambling in the late 90's for robotics / AI competitions where things like early versions of drones or other robots had to autonomously navigate a maze or move towards some particular target coordinates.

Basically, if nerdy robotics enthusiasts could circumvent the scrambling, surely a motivated enemy military or terrorist group could too. So, there wasn't much point in continuing it. Ending the scrambling was a good thing for Clinton to do, but I'm sure that impracticality played just as much if not more of a part in his decision as benevolence towards citizens of the Earth / potential economic rewards for American companies did...

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