We take for granted how easy it is to get around these days. A decade ago a big, fat Thomas Guide was the gift of choice - how else would you find your way around the city? Then TomTom, Magellan and Garmin came around. And now, with the proliferation of smartphones, maps of the entire world are in the palm of our hands.
But even when maps go awry, we tend to take the technology for granted. Here's an explanation of how GPS navigation works - so you can appreciate it a little more the next time it gets you where you need to be.