Originally Posted by
ok_commuter
High-end GPS units are pretty accurate. The consumer devices - stuff found in cell phones or those things people use on golf courses - less so, because the chips are smaller and less powerful. I've heard something like accurate to a 100' circle for that type. That said, I'm sure it's all getting better and more powerful by the day...
I've got an old Garmin handheld that was generally good to about 15' or so, unless it could only get a few satellites. Also, the error would usually go down if I stayed still a while.
The only time I noticed it be significantly off when it thought it was good was when I'd be near a tall building, putting all the satellites it could see on one side of the sky.