Quote Originally Posted by Neil View Post
Just completed the same 20km trip home in reverse. Left the 3590 in the glovebox, and used the 3790>3490 only. Cloud a little less, more few-scattered (2 to 3 eighths of sky covered) whereas outward trip was more like half sky covered. Mostly 5 metres, but sometimes 4 or very occasionally and briefly 6m. Acceptable accuracy and consistent. Very light traffic, only took 20 mins and able to watch the screen safely. So what's different in other users' units from Caty's and my unit, why are some ppl experiencing and reporting such high inaccuracies? I have a good chance to get a 3790 in the next few days to make a proper comparison.
I believe the issue may be temperature calibration. The Garmin units are factory programmed with a table containing timing compensation for temperature variations which is used to help with initial lock. This table is dynamic meaning it is updated overtime as the temperature varies and the GPS maintains a lock. The default provided table with the 34xx firmware seems different to the 37xx. On my unit it takes a few days, but the accuracy and lock on speed if the unit is left powered on.