Happy 20th Anniversary, GPS!


Today is the 20th anniversary of the Global Positioning System going live. We take it for granted today, but it remains one of the technological wonders of the modern world.

A visual example of a 24 satellite GPS constellation in motion with the earth rotating. Notice how the number of satellites in view from a given point on the earth's surface, in this example at 45°N, changes with time. Via WikiCommons

A visual example of a 24 satellite GPS constellation in motion with the earth rotating. Notice how the number of satellites in view from a given point on the earth’s surface, in this example at 45°N, changes with time. Via WikiCommons

The GPS system is a network of about 32 satellites that continuously broadcast the time and their location with extreme accuracy. The atomic clocks on each satellite are accurate to about 1 nanosecond.1 From the location of four or more satellites, a GPS receiver or even your smart phone call tell where you are to within a few feet.

Success of the GPS system involved the convergence of several technologies. Atomic clocks had to be perfected. Computer technology had to improve in speed and miniaturization. Software algorithms had to be improved. Satellite launching and orbital technologies had to be improved. That all started to come together in the 1990s, and has only improved since.

Now, an annoying, computerized voice can give you real-time directions for navigating your auto, re-calculate your route if you screw up and even direct you away from traffic jams. A hand-held GPS can walk you through the densest fog in the back country, and tell you precisely where you are. It’s almost impossible to get lost.

At least so long as the batteries last.

The technology is even more mature and more accurate than what mere civilians are permitted to use. The military, and those given encryption keys, have access to correction data that provides accuracy to a fraction of an inch. And there are augmentation systems that can improve civilian accuracy.

The GPS network is and remains a military program. It has disturbing uses, including targeting for cruise missiles, unmanned aerial vehicles and even GPS-guided artillery shells. Any technology can be used for grim, even evil purposes. But in the case of the GPS network, the good pretty clearly outweighs the bad.

It’s way cooler than flying cars.


  1. Atomic clocks use the steady decay of a radioactive isotope to calculate highly precise time. Those are the same radioactive isotopes that are used for geological dating. Anyone who claims the world is only a few thousand years old and uses a GPS has some explaining to do. 
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One thought on “Happy 20th Anniversary, GPS!

  1. The possibilities are endless with GPS. I remember when friends in the USGS in 1998 were talking about the possibility of layering information about every place on the planet with GPS and making it available to all. So much has come true!

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