Traffic Picture

traffic.TrafficPicture is one picture of all traffic around a centre of the world (#366): our controlled aircraft, MSFS AI and the user, with where each one is and what it is doing, and the airports inside the radius. The centre is fixed — an airport or a position — or follows the user’s aircraft; the library never assumes which.

picture := traffic.NewTrafficPicture(traffic.PictureOptions{
    Centre:   traffic.Centre{FollowUser: true}, // or {ICAO: "LKPR"}, or {Position: ...}
    RadiusNM: 250,                              // default DefaultPictureRadiusNM
})
lister := traffic.NewAirportLister(client, 0)
lister.Request()

for msg := range client.Stream() {
    if airports, ok := lister.Handle(msg); ok {
        picture.SetAirports(airports)
    }
    // … your aircraft scan (RequestDataOnSimObjectType) → []traffic.Observation
    picture.Observe(time.Now(), scan)
}

Feeding it

The picture is fed, not self-driving:

• Observe(now, scan) with each aircraft scan. SimConnect’s RequestDataOnSimObjectType reaches at most MaxScanRadiusMeters (200 km): MSFS AI farther away is not seen. Aircraft outside the radius, or not seen for PictureStaleAfter, leave the picture.
• SetAirports with the airports around, e.g. from AirportLister (SimConnect’s facilities list: the airports the simulator has loaded around the user, about 180 NM in MSFS 2024). AddAirport adds one it does not reach, such as a flight’s destination.
• SetOwn(objectID, phase, icao) for the aircraft our controllers drive — they know their phase best; ForgetOwn when a controller lets go.

Centre

A fixed centre stays put; SetCentre moves it, SetRadius changes the radius. A centre following the user moves only once the user is RecentreNM (25 NM) from it, so the picture does not churn with every scan.

What it knows

Aircraft() — nearest to the centre first — gives each aircraft’s scan data with its phase and airport:

An aircraft on the ground belongs to the airport within AirportNearNM. Airports() are the airports inside the radius with their distance from the centre. Events() reports aircraft and airports entering and leaving, and recentring (dropped when the channel is full; the picture itself stays current).

Feeding the controllers

• Ground(icao) is the GroundPicture of an airport, shared by its controllers (TaxiWithGroundPicture, ArrivalWithGroundPicture; see Ground traffic). Observe reports the aircraft on the ground there that are not ours; ours report themselves.
• Allocate(icao, allocator) feeds a StandAllocator (Stand allocation) from the picture’s scans, so it needs no scan of its own.
• ManagerOptions.Picture gives it to the Traffic Manager, which counts the aircraft that are not ours as other traffic and follows its own airborne flights in it.

On the airport map

The Map section has the Traffic picture: the centre (follow my aircraft, this airport, or the map centre), the radius, the airports and aircraft in range by phase, and the load of the aircraft we drive. The 🌐 button (bottom left) is the world view (#371): the map zooms out to the picture’s circle and shows the airports in range and every aircraft, coloured by phase and labelled with call sign, level, phase and destination. Other traffic appears there only when its layer is on. Press 🌐 again to go back to the airport. The airports in range fill the ICAO fields (Load, flight plan) as a dropdown. GET /api/world returns the picture; POST /api/world sets the centre ({"follow":true}, {"icao":"LKPR"}, {"lat":…,"lon":…}) and the radius ({"radiusNM":250}).