GPS & AIS Jamming in the Strait of Hormuz

Look at any live ship map of the Gulf since mid-2026 and you'll see impossible things: tankers parked on Iranian mountainsides, ships teleporting fifty kilometres between updates, whole convoys sailing in neat circles. None of it is real. It is what electronic warfare does to the two systems that ship tracking depends on. This page explains the mechanics in plain language, and what it means for any data — including ours — derived from AIS.

Two systems, two failure modes

GPS (GNSS) tells a ship where it is. AIS broadcasts that position, along with identity, course and speed, so other ships and coastal receivers can see it. Interference attacks each differently:

• GPS jamming drowns the weak satellite signal in noise. The ship's receiver loses its fix; its AIS then broadcasts stale, missing or garbage positions. Crews navigate by radar and inertial systems, but the tracking picture degrades.
• GPS spoofing is subtler: a transmitter broadcasts counterfeit satellite signals, so the receiver computes a confident but false position. Spoofed ships report positions on land, or drift in geometric patterns — the famous "circle spoofing" — because every victim in range inherits the same fake solution.
• AIS manipulation and dark transits are done by the ship itself: switching the transponder off ("going dark"), or transmitting a false identity or position. Sanctioned-oil carriers were doing this in the Gulf long before the war.

Who is jamming, and why

Attribution for any single incident is genuinely hard, but the broad pattern in a war zone has three drivers: militaries degrade GPS to defeat drones and precision weapons; navies and ports spoof to complicate targeting of high-value anchorages; and commercial operators go dark or falsify tracks to move sanctioned cargo or simply to avoid being a target. The result is the same either way — the AIS picture of the strait stopped being a reliable census of what's actually sailing.

What it looks like in the data

• Position jumps of tens of kilometres between 30-minute polls, implying impossible speeds.
• Clusters of ships reporting from dry land near Bandar Abbas.
• Vessels that enter the strait and never report again — then reappear days later on the far side, or not at all.
• Coverage holes: since 12 July 2026 our upstream source has served very few positions in the western strait's traffic lanes, hiding transits that certainly happened.

How this tracker compensates

Our crossing detection was rebuilt in late July 2026 around the assumption that tracks will be incomplete:

• Zone-transition inference: a crossing is counted when a vessel is seen in the Persian Gulf and later in the Gulf of Oman (or vice versa), even if every position in between was lost — it does not need a clean track through the strait.
• Anchorage-transit rules: vessels that dwell at Bandar Abbas anchorages and then appear on the far side are classified using dwell-time logic rather than discarded.
• Sanity filters: physically impossible jumps are treated as noise, not movement.
• Lower-bound framing: everything we publish — crossing counts, oil-flow estimates — is presented as a conservative floor, because a dark or jammed transit can evade any inference.