It's interesting to note that the first in-car navigation system used no GPS: it relied solely on inertial navigation and map-fitting to determine its location. For navigation, an autonomous car needs something like that as backup for GPS. All the actual driving needs to be done with on-board sensors, though.
I'd be surprised if the lidar units aren't being used for a similar algorithm.
https://www.fastcompany.com/3047828/who-needs-gps-the-forgot...
Live demo: https://www.youtube.com/watch?v=CHCCjlSWbHE
> Cheap dead reckoning sensors have so much error and drift right now as to be mostly useless for driving.
I don't think anyone's saying that it would be used for the driving part (i.e. car control), just as an option for orienting the car in the wider world beyond its direct perception.
Unless your "true-AI" stops to ask locals for directions, its going to need some sort of GPS. Can't say I'm looking forward to arguing with my car about how it should have taken a left on Main St, instead of a right.
GPS ≠ navigation assistance. You can infer where you are on a conceptual map from reading your surroundings, especially signage. Getting a latitude/longitude estimate from the GPS network and trying to match it with an overly precise and possibly out of date map isn't the only way to infer your current position. It's only useful when you don't already know where you are, and computers are good at precisely remembering the path they took from the last known observed reference.
Plus, self-driving cars need to be aware of their surroundings, and not solely rely on blindly following a hyper-precise map as a prescription of the road details ahead. Having the local observations become the canonical precision knowledge, and keeping the map as conceptual knowledge of how roads connect places, implicitly gains a lot of this sort of benefit.