Originally Posted by
rfg17 I've noticed that sometimes the error circles are bigger than others and that rebooting helps get back to normal. I suspect this is a memory usage issue that affects how well the phone can compute position given the GPS signals.
The circle is actually improved by A-GPS. The A part is cellular/wifi. don't reboot, just go into airplane mode and it reconnects to the towers and updates this date.
You get better wifi data in dense areas, you get better cellular data in the country. It also works better when driving because it can follow the roads. If you turn and there's a road it's hard for it to get your location wrong if it moves the dot to a new road. It's also using the changing signal times from the cell towers to get your movement speed right. Get off road, say on a ferry, and it moves around for a bit even with a good signal near shore and may never be right.
The reason for the good location data in Manhattan is the wifi data. The tall buildings are blocking most of the GPS signals and cellular signals likely bounce some. they're just using gps to narrow down your location some more