1. What TankerMap is receiving

TankerMap's canonical fleet database contains 7,245 tanker profiles; 5,391 have a latest observation within the past day and 6,154 within the current live freshness window. A position timestamp describes when the vessel was observed, not a promise of continuous coverage.

2. What an AIS message contains

Automatic Identification System transponders broadcast dynamic fields such as position, course, speed and navigation status, plus static or voyage fields such as MMSI, IMO number, ship name, type, draft and destination. Update frequency varies with vessel movement and equipment class. Some fields are entered manually and can be stale, misspelled or intentionally misleading.

3. Terrestrial and satellite reception

Coastal receivers generally provide frequent updates within radio range, but geography, antenna coverage and message collisions create gaps. Satellites extend coverage offshore, yet crowded sea areas can still produce collisions or delayed delivery. Aggregated tracking systems combine multiple receivers and providers, so two websites may show different last-seen times without either inventing a position.

4. Why a tanker appears to go dark

A gap can result from weak reception, satellite scheduling, congestion, equipment failure, maintenance, power loss or an intentionally disabled or manipulated transponder. A missing message alone does not prove sanctions evasion or illicit activity. Strong analysis combines the last reliable position, the next reliable position, elapsed time, feasible speed, port events and other independent evidence.

5. How to interpret a live map responsibly

Check the observation time before interpreting a marker as current. Compare identity fields across IMO, MMSI and name because MMSI and names can change. Treat destination as a crew-entered signal, not a verified contract. Use track history and chokepoint analytics for movement evidence, and read how TankerMap tracks tankers for the practical workflow.