Positioning validity life cycle

Return positioning and time authoritative model

stateDiagram-v2
  [*] --> NoFix
  NoFix --> Candidate: sample
  Candidate --> Valid: accepted
  Candidate --> NoFix: rejected
  Valid --> Stale: freshness deadline
  Stale --> Valid: fresh sample
  Valid --> NoFix: source lost

Some coordinates are not equal to Valid; Stale cannot continue to pretend to be a real-time location.