UNIX for Dummies Questions & Answers

Precise timekeeping is how GPS work. The satellite knows very exactly where it is and what time it is. It sends you a signal and you know when you recieved it. That enables you to draw a sphere around the satellite and you know that you are on the sphere. Do that with a second satellite and you have two spheres which intersect on a circle. Now you know that you are on that circle. A third satellite will have a sphere that intersects that circle at 2 points. A fourth satellite will have a sphere that intersects one of the 2 points. And you are on that point. This over-simplifies the process but it's close enough to give an idea of how it works. Each satellite has several atomic clocks on board and the US Naval Observatory scans each satellite once a day and possibly adjusts them to keep them synced with the USNO Master Clock.

Just out of curiosity, interesting are there any watches that read time off the satellites? It would be definitely 007 style of equipment !

A few. Search for GPS watch on Amazon.

That's COOOOL! When I pass my next unix academy exam exam, I'll think of rewarding myself! But they are quite expensive for electronic watch!

Perderabo, thanks man! I love gadgets!