GPS Review explains how street-navigation GPS receivers appear more accurate than they actually are by using a “snap-to” feature that aligns the user to the nearest road. I’ve seen this happen with mine on more than one occasion; it’s interesting when it gets confused at interchanges. (It also has to be switched off if you’re recording GPS tracks for OpenStreetMap, or you’ll simply replicate the unit’s copyrighted map data. More on that at some point.)

The GPS system’s real accuracy is apparently about to get better, with the launch of the IIF generation of satellites, says Wired: “A three-signal world will mean always-on GPS that’s accurate to within 3 feet, even indoors and in concrete urban canyons. Forget finding the bar; you’ll be able to geolocate your stool.”