AIS Integrity Watch

Where the world's positioning signal stops being trustworthy, week by week. Five heuristics over public AIS, aggregated by zone.

Live aisstream.io sampling sessions, all six zones at once · aggregated by zone only, never a vessel name, MMSI or IMO · history accumulates weekly

Anomalies flagged · W43

+8 vs W42

Gulf of Guinea · W43

highest zone this week

Vessels observed · W43

across 6 zones, 12 min of listening

Zones × weeks

Flagged anomalies per zone per week, all heuristics combined. The brighter the cell, the noisier the zone.

Zone	W29	W31	W32	W35	W36	W37	W38	W39	W40	W41	W42	W43
Strait of Hormuz	0	0	0	0	0	0	0	0	0	0	0	1
Black Sea	4	8	5	12	14	14	17	15	17	16	10	10
Gulf of Finland	7	14	7	6	20	12	12	49	4	11	4	9
Eastern Mediterranean	23	6	23	22	9	11	40	6	11	5	9	7
Southern Red Sea	0	0	0	0	0	0	0	0	0	0	0	0
Gulf of Guinea	0	1	0	0	1	0	0	2	21	14	11	15

Live sampled AIS via aisstream.io · Graphic: Le Phare

What kind of noise

Weekly totals by heuristic, from the same sampled sessions. Interference clusters and displaced positions concentrate where the shooting is; the rest is the long tail of a degraded signal environment.

Live sampled AIS · Graphic: Le Phare

The five heuristics

Jamming cluster: Many vessels in one area simultaneously reporting displaced or circular positions: the signature of area GPS interference, not of any single ship.
Impossible jump: A position sequence implying a speed no hull can reach. Flags teleporting tracks caused by spoofed or corrupted broadcasts.
Speed anomaly: Reported speed over ground far outside a vessel class's envelope, sustained across several messages.
Dark gap: A prolonged silence from a transponder inside a sensitive zone, bounded by normal broadcasts before and after. Counted only above a duration threshold.
Position on land: Broadcast coordinates that place a vessel solidly inland. Almost always interference or spoofing; occasionally a misconfigured transponder.

How the watch samples

Each week the pipeline opens one live aisstream.io connection covering all six zones and listens for a bounded session (~12 minutes), applying the five heuristics to the raw position stream in memory. Only zone-level counts are kept. Sampling means the numbers are a floor, not a census — comparable week to week because the method never changes, and biased low everywhere shore-receiver coverage is thin (Hormuz notably, where jamming also suppresses reception).

This module never names a ship. Anomaly detection points at zones and signal environments, not at vessels: attribution from open AIS alone is unreliable, and this observatory does not do name-and-shame.