michinyon:
It is ususual for the actual measurement error to be as large as 200 metres.However, I have noticed that the measured GPS position sometimes wanders away from the correct position,
and then gets "stuck" maybe 200 metres away and it won't come back. Thats if I stand still. But then
if I walk around a bit, it will suddenly come good, maybe ten or 15 minutes later.I used to get this often, when I got off a train. The GPS reading would overshoot the station, and stop
several hundred metres down the track. I was told that this was a "feature", to prevent the apparent
position of cars shifting while they were stopped at the traffic lights.
I've got to figure this out. I took it out for a quick drive last night and got this course plot. Last I checked, my car isn't amphibious. I'm going to take it out for a while today and see if it can figure itself out. Interestingly enough, amidst all of that jumping around, I can make out segments of the course that I actually drove but it is offset from my actual position by a fixed amount at some points in the track but then it jumps to a different offset amount.
Screen Shot 2013-01-21 at 7.41.10 AM by jg1996business, on Flickr