Data Sources

Vessels are tracked from two primary sources: AIS (Automatic Identification System) via AISStream, which provides real-time position, speed, heading, and destination data broadcast by vessels themselves; and port authority schedules from NSW Ports, Ports Victoria, QShips QLD, Fremantle, Flinders (SA), Darwin, and TasPorts, which provide forward-looking arrival schedules. AIS data is polled every 10 minutes from a 2-minute WebSocket window covering the Australian bounding box. Port schedules are scraped every 6 hours.

Vessel Identification

Only tanker-class vessels are tracked. We filter for AIS ship type codes 80–89 (tankers) and exclude gas carriers (LNG, LPG, GASCHEM) via name pattern matching and ship type codes 70–79. Each vessel is identified by its unique MMSI (Maritime Mobile Service Identity). Where available, IMO numbers are cross-referenced for enrichment.

Fuel Type Classification

Fuel type is determined through a classification cascade, in order of confidence:

1. Port scraper vessel type — e.g. “Oil Products Tanker”, “Crude Oil Tanker” (highest confidence, verified)
2. Berth assignment — specific fuel terminal berths (e.g. Bulk Liquid Berth, Kurnell, refinery jetties)
3. Origin port — crude origins (Fujairah, Ras Tanura) vs product origins (Singapore, Ulsan)
4. AIS ship type code — types 81–84 (hazardous/crude), 80/85–89 (generic/products)
5. Vessel name keywords — e.g. “diesel”, “jet”, “aviation” (lowest confidence)

Product Tanker Cargo Split

Generic tankers (AIS type 80) and product tankers (type 85–89) carry mixed refined fuel. Without cargo manifest data (which is not publicly available), their cargo is split proportionally based on Australian Petroleum Statistics import mix: 57% diesel, 25% petrol, 13% jet fuel, 5% other. This is a national average and may not reflect individual vessel loads.

Cargo Volume Estimation

Cargo volume is estimated from AIS-reported vessel dimensions (length × beam) using a cubic number approximation for laden tankers. Where available, known DWT (deadweight tonnage) from vessel databases is used instead for higher accuracy. Port scraper data does not include cargo volumes. Cargo manifests are not publicly accessible in Australia.

Destination Confidence

Potential Diversions

A vessel is flagged as a potential diversion only when there is positive evidence: its AIS destination changes from an Australian port to a non-Australian port while the vessel is more than 200km from the Australian port. Vessels that arrive at an Australian port and then depart for their next destination are not counted as diversions. Vessels that go quiet on AIS (transponder off, coverage gap, or arrived at port) are not assumed to be diverted. Potential diversions may reflect commercial rerouting, schedule changes, or data corrections — not necessarily supply disruptions. Arrivals are verified via Data Docked port call history where available.

Distance & Route Calculation

Distance to port is calculated using the haversine (great circle) formula with route correction factors applied per transit zone. Vessels transiting the Strait of Hormuz, Singapore Strait, or Indonesian passages have correction factors of 1.15–1.25× applied to account for actual maritime routing vs straight-line distance. Routes displayed on the map are interpolated great circle arcs routed through key maritime waypoints (Lombok Strait, Bass Strait, Cape Leeuwin) to approximate realistic shipping lanes.

Limitations

Cargo type and volume are estimated, not confirmed — cargo manifests are not publicly available in Australia. AIS data can be delayed, incomplete, or in rare cases spoofed. Port schedules may change without notice. Vessel dimensions in AIS can be inaccurate or missing. The product tanker cargo split is a national average and may not reflect individual vessel loads. Vessels not broadcasting AIS (transponder off, out of range) will not appear. Scheduled vessels from port authorities may not materialise if bookings are cancelled.