Real GPS is accurate to 33 feet lat/lon and 16 feet vertical. How accurate is the cell phone pseudo-GPS?
Don’t know.
Many modern Cell phones have REAL GPS built in - that is certainly the case with my new Samsung u540. Google is talking about a system that can get you within 10 blocks of your location by using the cell site signal strength - which is maybe what you are talking about?
I can tell you that Verizon offers a service for GPS enabled phones that can do the Navigation trick all by themselves. At the same time - I just bought myself a TomTom and love it! The only problem is that it isn’t compatible with the u540 - knew that going in. Maybe a reason for switching cell providers when the contract is up... time will tell.