Jamie's Blog

Ruby developer. CTO. Swimmer. Always trying to write more

Your sat-nav doesn’t spy on you

Based on a report by the Information Commissioner, Jeremy Vine on Radio 2 spent a good portion of his show talking about the surveillance society that the UK has become. Fair enough, there’s probably something to that. However, he also kept going on about your sat-nav’s tracking you.

For once and for all, GPS devices are receivers only! It works like this: GPS satellites broadcast the current time, your device receives these broadcasts from multiple satellites, calculates distances based on the elapsed time, and performs some complex variant of trigonometry to figure out your position. At no point does your sat-nav report your location to US military satellites so that Mr. Bush can keep an eye on you. That’d be like suggesting that the BBC can tell what radio station you’re listening to or what TV channel you’re watching!