One thing really annoys me about these explanations. GPS units don't know the time accurately enough to do what they say. Instead, they compute the difference in the received timestamps, which gives the difference in the distances to the satellites. That puts you on a hyperbolic paraboloid. Enough of them and you can pin down your location.<p>Some GPS units work by iterating to a solution, effectively computing the time, but it's not as easy as simply knowing the time and computing the distances.<p>The real explanation is more complex, and way cooler. I wish people wouldn't simplify in a way that makes it almost trivial and loses the good bits.