MAP messages promise lane-level intersection awareness, but a roadside broadcast is only as trustworthy as the software pipeline that reconciles it with the vehicle's own sense of where it is. This article walks through that reconciliation pipeline end to end.
The matcher treats both the MAP lane graph and the HD-map lane graph as directed graphs and runs an iterative closest-point alignment on their centerline polylines, scoring candidate lane pairs by heading similarity, width consistency, and connectivity topology before committing to a match above a calibrated confidence floor.
When onboard lane-marking detection disagrees with the MAP-derived lane assignment by more than a calibrated tolerance, the fusion module downgrades the MAP input from an authoritative source to an advisory-only hint, preventing a stale or vendor-misconfigured MAP broadcast from ever overriding what the vehicle's own sensors currently observe.