To follow Diamond S Shipping Group ships across the globe, the Center for Public Integrity analyzed data from an automated ship tracking system relied on by maritime authorities. Automatic Identification System (AIS) beacons, required by treaty on seagoing ships that trade internationally, continually broadcast a ship’s location and identification numbers. The beacon signals are captured by coastal base stations and orbiting satellites, then resold to the public as data points.
The Center asked MarineTraffic, a global ship tracking intelligence provider, for AIS data showing port calls for the 45 ships in the Diamond S Shipping fleet during six years starting just before 2012, when Wilbur Ross’ firm invested in Diamond S Shipping. MarineTraffic provided more than 5 million data points showing the movements of those ships across oceans, between continents and down coastal rivers. The Center for Public Integrity reproduced those points on a map, then searched for ships docking in specific countries, including Iran, Russia and China.
The AIS data does not provide perfect coverage: satellites can miss signals and are occasionally confused by noise, and according to a Reuters report, although the system is required, ships can silence the beacons when captains don’t want to be tracked, and ship identification signals can be falsified with some effort. The Center for Public Integrity found gaps in the data consistent with partial coverage, but nothing suggesting deliberate manipulation.
To verify some data, the Center for Public Integrity relied on other documentation, including an investigation by the Hong Kong Marine Department to corroborate a ship’s location near an Iranian port, a trip that was confirmed by Diamond S representatives after the Center submitted questions about it.