1. The observation universe

Chokepoint detection draws from the same canonical observation history that supports 7,245 public tanker profiles. Coverage is not uniform: 5,391 vessels currently have a latest observation within one day, while older tracks may contain gaps. Transit counts therefore measure detected crossings in the available observation record, not every physical ship movement worldwide.

2. Crossing is different from presence

A vessel near a strait is not automatically a transit. A robust detector needs evidence that the vessel moved from one side of the passage to the other in the correct geographic context. This prevents anchored ships, coastal traffic and repeated points inside a broad area from being counted as crossings.

3. Direction, event time and AIS gaps

Direction is inferred from the ordered observations on opposite sides of the passage. The transit event receives one timestamp so it can be grouped into daily analytics. A bounded time window limits accidental matches between unrelated visits months apart, while gap-aware logic can still recognize a crossing when AIS reception disappears inside the narrow passage and resumes on the other side.

4. How duplicate counts are avoided

Repeated provider messages and dense position tracks can describe the same physical crossing many times. TankerMap normalizes observations to a canonical vessel identity and stores one transit event per crossing episode. The same vessel may correctly appear again after it leaves, later returns and completes another crossing; it should not appear twice for one episode simply because two providers observed it.

5. How to read the charts

Daily values can change when late positions fill a gap or a replay recomputes the same approved method. Compare completed UTC days and the displayed vessel segments rather than treating an in-progress day as final. Open Strait of Hormuz analytics or the strait dashboard to inspect current counts.