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National Geographic Channel Gets GPS Wrong?

Apr
1
2009

I was catching up on some DVR recordings recently and one of the shows I was watching started talking about GPS. The show I was watching was titled Known Universe on the National Geographic Channel. Specifically, it was the episode titled “The Fastest”. The show was focusing on things that happen (literally) at the speed of light, and they started to describe how GPS works. They said this:

The signal from the GPS device travels at the speed of light to a satellite in space. The satellite measures how long the signal took to reach it to determine the distance.

I know quite a bit about GPS, but I’ve never proclaimed to be an expert on all of the involved physics. But I do know the description above sure sounds backwards to me! I think it would have been more accurate to say it this way:

The signal from the GPS device satellites travels at the speed of light to a satellite GPS receiver in space on earth. The satellite GPS receiver measures how long the signal took to reach it to determine the distance.

While the TV show wasn’t geared towards kids, the following video was and it does a much better (and more accurate) job of describing how GPS works.

One Response


  1. That is funny, I noticed the EXACT same thing. While I like this show, there have been some other errors (this indeed IS an error, there is NO transmission from the terrestrial device TO the satellite, the GPS SAT sends a TIME STAMP with the information, that is why the device must be coordinated and why the GPS SAT time stamp must run in a bit advanced. Good catch though.

    tivoboy - April 1st, 2009



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