Every vessel on the ocean broadcasts its identity and location using the automatic identification system (AIS), which is mostly used to prevent ships from colliding. These days it can also be used to track ship locations, as most AIS data is relayed through satellites. If you want to hide on the sea, the first thing you do is make your vessel "dark" by turning off your AIS broadcasts. What's interesting about pirate fishing vessels, however, is that they need to rendezvous with legitimate reefers if they want to get paid for their catch. To find the pirates, Amos told Ars, he and Bergman needed to look for odd patterns in the behavior of reefers. The group partnered with Global Fishing Watch to work on mapping satellite AIS data, and those patterns began to emerge. "Often with reefers they come to a halt in the middle of the ocean," Amos said. "We don’t see other broadcasting vessels, but we can be confident based on what that ship is doing that they must be rendezvousing with dark vessels." <https://arstechnica.com/tech-policy/2017/02/to-catch-a-thief-with-satellite-data/> I guess this counts as a “big data” application...