Multi-source fusion
No single ADS-B network sees everything, and several see the same aircraft at once. Here is how several public ADS-B networks become one coherent track per airframe.
One receiver network is always an incomplete view
An ADS-B broadcast travels line of sight. A ground receiver typically hears aircraft out to roughly 200 to 300 nautical miles depending on antenna height and terrain, and nothing at all beyond the horizon. Every volunteer network is therefore a patchwork of local bubbles, dense where people live and thin everywhere else.
Two consequences follow. First, any single network has gaps that a different network may happen to cover. Second, in busy regions several networks hear the same aircraft at the same moment, and their reports will not agree perfectly: timestamps differ by fractions of a second, one may carry a callsign the other lacks, and a marginal reception can produce a garbled field.
Naive merging makes this worse rather than better. Concatenating feeds gives you the same airliner three times. Averaging positions invents a location no receiver actually reported. Fusion has to be deliberate.
Ingest, key, reconcile, serve
| Stage | What happens |
|---|---|
| Ingest | Live traffic is pulled from community networks including adsb.fi, adsb.lol, airplanes.live and OpenSky, scoped to the map area actually in use so upstream load stays proportionate. |
| Key by ICAO | Every report is grouped by the aircraft's 24-bit ICAO hex address. This is assigned per airframe and carried in the message itself, which makes it the only reliable join key across independent feeds. Callsigns are not usable for this: they change per flight and can be reused or spoofed. |
| Reconcile | Where two networks describe the same airframe, the most recent well-formed report wins, and fields missing from it are filled from the next best source. Self-inconsistent messages are flagged by the integrity checks rather than silently blended into an average. |
| Serve one track | A single de-duplicated aircraft is emitted, with the views from each ground network reconciled into one position, then passed to enrichment and scoring. |
Coverage and trust at the same time
Wider coverage. Overlapping networks fill each other's gaps, but no ground network reaches mid-ocean, so those regions stay empty. Where a single feed would show an aircraft vanishing mid-route, fusion often keeps the track continuous.
Better data per aircraft. One network may carry the callsign, another the vertical rate, another a cleaner altitude. Reconciliation assembles the most complete record rather than accepting whichever feed answered first.
A cross-check on trust. Independent networks disagreeing about the same aircraft is itself a signal. Fusion is the layer that makes that disagreement visible, and it feeds directly into the integrity and spoofing checks and the attention score.
What fusion cannot fix
- Fusion cannot see an aircraft that never broadcast. If no network heard it, merging networks does not help. See limitations.
- It does not authenticate anything. Agreement between feeds means they heard the same broadcast, not that the broadcast was truthful.
- Coverage still collapses over open ocean, deserts and polar regions where no ground receiver exists. See coverage.
- Upstream outages propagate. If a major network degrades, the fused picture thins with it, which is why the status page exists.