They tend to produce the same routing that you'd
get from something like Mapquest or Google.
Keep people on major thoroughfares, commonly
traveled paths etc. Neat shortcuts that the
'locals' use aren't in the database but they
won't dump you on a one-way street going the
GPS accuracy has been damn good. Usually within
75 feet. OnStar folk identify vehicle location
to nearest street/intersection so actual
accuracy in the vehicle's electronics is
probably better. I'd chalk that up to better
antenna coverage than you get in a portable.
Big plus with OnStar Nav over something like
Garmin or Tom-Tom is current road-closure info.
Easier than screwing with a cell-phone to
CalTrans or Nevada's Highway Dept. They only
missed once in perhaps a dozen road closure
checks and that did cost me a 'double-back' for
Wasn't using it often enough to make it a great
value and reverted to paper maps and the phone.
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