I've bee using GPS systems for years. I usually find accuracy problems arise in two situations:
1) Not enough satellites connected (3 connections work, but not well).
2) Maps.
The worst case of (2) I found was on vacation in NM. The map seemed to be off by 100-200 feet. I kept passing turns before the GPS flagged them. It was a real nusiance.
Interestingly, my portable GPS was accurate enough to flag a speedometer error of almost 5 MPH on one of my cars. It was confirmed by one of those radar warning stations along one of the road.
Gary
1) Not enough satellites connected (3 connections work, but not well).
2) Maps.
The worst case of (2) I found was on vacation in NM. The map seemed to be off by 100-200 feet. I kept passing turns before the GPS flagged them. It was a real nusiance.
Interestingly, my portable GPS was accurate enough to flag a speedometer error of almost 5 MPH on one of my cars. It was confirmed by one of those radar warning stations along one of the road.
Gary