trail-mate/docs/models/positioning-time/fix-lifecycle.md

GNSS revision processing chain

sequenceDiagram
  participant Driver as GNSS byte source
  participant Service as LocationService
  participant Parser as NmeaParser
  participant Filter as GpsJitterFilter
  participant Events as ILocationEventSink
  participant Time as ITimeAuthorityUpdater
  Driver->>Service: onGnssBytes(bytes, len, now_ms, last_motion_ms)
  Service->>Parser: parse input / observe revisions
  alt fix revision changed
    Service->>Filter: evaluate LocationFix
    Service->>Events: publish accepted fix event
    Service->>Service: update latest_fix_ and last_fix_revision_
  end
  alt time revision changed
    Service->>Time: update time authority
    Service->>Service: update last_time_revision_
  end

This is not a NoFix / Valid / Stale state machine; the current model uses revision, filter and output ports as facts.