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vehicle-coordinate-interpolation.md

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Vehicle coordinate interpolation (#1109 / #1323 / #1341)

Between arrival polls the trip-page (and stop-route-focus) vehicle marker interpolates when the hop is short, and snaps when it is not.

Thresholds

VehicleCoordinateUpdate has three branches:

  • ignoreBelowMeters — hops smaller than this are left alone (noise).
  • interpolate — city-block hops animate for animationDuration.
  • snapBeyondMeters (500 m) — longer hops teleport. A bit over one 30 s poll at ~50 km/h (city-traffic tuning). At exactly 500 m the comparison is >, so that hop still animates; freeway / express buses usually snap.

Docs and tests describe the constants, not a motorway-speed framing.

Apply path

Callers that assign VehicleAnnotation.tripStatus must restore the previous coordinate before VehicleCoordinateUpdate.apply, because tripStatus's didSet writes lastKnownLocation immediately and would otherwise skip the animation. Used by:

  • TripFocusMapLayer.drawVehicle (removes the pin when the feed omits a coordinate)
  • StopVehicleAnnotation.update
  • TripViewController.currentTripStatus (legacy trip screen; same remove-when-nil policy as the focus layer — fixed in #1341)