By combining the AIS data with vessels detected from night lights, we can reveal broader patterns of activity in the ocean. Using a sophisticated matching system built on a method described in this paper, we have identified which of these lights correspond to vessels broadcasting their positions and which lights are not tracked by our systems. Processed over the past decade, it includes more than 100 billion GPS positions broadcast from vessels over the automatic identification system (AIS), spanning more than 70,000 fishing vessels and a few hundred thousand non-fishing vessels. To answer those questions, we turn to our massive dataset of vessel positions. To further challenge our observations, the data only tells us if a vessel is present and how bright it is-without revealing the type of vessel or what it might be doing. Clouds and reflected moonlight also limit our observations. One challenge is that the imagery is relatively low resolution–every pixel is 750 meters wide and contains enough room for more than one vessel.
The VIIRS sensor detects lights at night, but it takes work to determine which lights are likely from vessels.
This database of lights has helped us reveal widespread illegal fishing in North Korea, track the squid fleet operating near the Galapagos, and reveal vessel activity globally. Our research partners, Chris Elvidge and his team at the Earth Observation Group at Colorado School of Mines have compiled nighttime satellite imagery into a global database cataloging where these bright lights appear on the ocean. A NASA satellite, the Suomi National Polar-orbiting Partnership, carries an extremely sensitive camera, the Visible Infrared Imaging Radiometer Suite (VIIRS), which images the entire earth’s surface every night. The satellites that monitor the earth work around the clock, making it possible for these boats to be seen from space. Some vessels, like squid and purse seine, use lights to attract catch to the surface. Vessels often are equipped with bright lights to illuminate the deck or surrounding ocean, allowing crew to carry out their work in the dark night hours. And every night, satellites snap a picture of all the activity taking place down below, including vessels at sea. When the sun sets, human activity on the ocean goes on. Data Source: Earth Observation Group, Global Fishing Watch New Global Fishing Watch technology merges nighttime images with GPS datasets to observe vessels not broadcasting their positions Vessels detected with the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor between 20, matched to automatic identification system (AIS) signals, reveal large, previously unmonitored fleets.
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