I live in a very rural area where houses and intersections were at least 1000 feet off from my GPS. My house showed up over a mile from the road and the the road was labeled with the wrong name.
Then one day about 4 or 5 years ago everything was accurate. Super accurate as a matter of fact. I looked at the little man icon on the map, clicked it and noticed that a Google Street View car, or whatever they're called, drove by a couple months before that (based on what was shown in the picture) and the maps were updated. When the maps were wrong, street view was not available in my area.
I would also assume Google, and everyone else, takes GPS readings from your phone and updates maps where they haven't sent their own equipment.
The problem you envisioned will be corrected long before the first snowfall and an autonomous vehicle meet.