Originally Posted by DaleDe
Once the GPS is locked on it is correct. Maps are a different matter. Some mapping programs use road lock to pull the location to the nearest road and sometimes get this wrong, particularly if the two roads are not the same size. Other factors include the fact that most maps are really wrong. They were made before GPS and not updated. Of course many phones use a really poor implementation of GPS using poor antennas and minimum hardware depending on other methods to fill in the gap. Your Garmin is much better. Garmin now makes a Bluetooth model for the iPad, iPhone now that includes both the US and the Russian satellites for even better accuracy. It is called GLO and has the special Apple proprietary features needed to make Bluetooth work.
My Garmin Zumo is Bluetooth enabled, so it connects wirelessly to my helmet speakers. But I never thought to try to see if it will connect to my phone. I'll give that a try!