Lane markings are a fraction of the triangulation.

We ourselves identify and confirm other urban waymarks via captcha which feeds the nav data -- bridges, signs, hills, hydrants, chimneys, lights. There is mass live verification from android auto in vehicles. There are many yearly layers of street view images and scans.

Right, and what about rural waymarks? A highway in the middle of nowhere at night during a snowstorm?

I don't think we'll see a system that can handle that in my lifetime.