That's easy if you're not, say, in a winding, narrow, deep canyon, such as you might find in a mountain pass. Which is, for related reasons, the same place you'll find the heaviest snow cover. Also for related reasons, "well mapped areas" are around where people live, as opposed to - again - places where you could expect uncleared snow.

"Works great near my house, might accidentally kill you if you try to ride it outside the happy path" is somewhat underwhelming.

That's assuming a very accurate GPS in very good conditions. You also need to be sure that there aren't any road works that would temporarily change the lines. Seems a bit risky to commit 100% to the GPS for that.