Re: And I need this why?
"the use case is for autonomous vehicles"
Not really - a disaster for an autonomous vehicle just relying on GPS and its maps - need to react to changes in roads that will not be on its map - be that a new road, or (if we assume fantasy world of fast, frequent & accurate map updates) things like contraflows due to roadworks where you can easily end up on the "wrong" road e.g. on motorway work, in some worst case scenarios* may have all of Northbound motorway closed and traffic heading "North" forced to use a (coned off) lane of the "Southbound" motorway (& traffic heading South forced to have less lanes).
Other fun situations are where roads are at different heights, so in our nice 3D world can get stretches where road A is above road B for a while (in some cases a few 10s of metres), but can be a few km sometimes. These scenarios have caused confusion in my SatNav where it gets confused on what speed limit should be - will it decide on the 70 of the A road dual carriageway I am on or the 30 of the B road below.
Any autonomous vehicle should be fine without GPS (just like a human, people managed OK without SatNavs for a long time & any driver with any sense treats them as a useful tool when travelling somewhere unfamiliar, but definitely not as an infallible source of road truth) - and be able to cope with just "looking" at the road layout and signs,
* 2nd worst case, worst ones are when whole Motorway closed in both directions... But worst case as far as autonomous cars are concerned.