A radius of 5 meters- 15 feet or so. Which of you consider the scale of what’s going on (satellites in orbit, pinging your location to a relative pin prick, accounting for relativity,) it’s fucking impressive.
But you might be anywhere along a thirty foot line.
And that’s at its most optimal conditions. Inside a building (particularly commercial or industrial, and particularly larger buildings,) that becomes much, much more problematic.
Which is why they use combinations of things like WiFi location (“improved location services”) to increase accuracy as well as dead reckoning using your accelerometer.
But ultimately, that’s all just a guess, and they’ll frequently cheat. For example, if you pull under an overpass and stop, pretty quickly they’ll start wigging out bouncing you between the road above you or the one you’re actually on. Or when you decide to ignore navigation instructions on the highway- which is why until it updates the map it’ll still show you on the offered route. (Which might be 200 ft down the road, and 50ft away.)
All of that to say that they’re using a lot of tricks to convince you that it’s a lot more precise than it really is.