Sat-nav eroding local knowledge

Sat-nav feels like state-of-the-art technology, but it's a century since the first auto-navigation device was invented and, says BBC's Joe Moran, there are fears such systems are starting to erode local knowledge. This has interesting implications for space and our understanding of augmented reality, and the layering of virtual data over real places, particularly if systems could start to fail from next year as the US Air Force's satellites deteriorate. More here.