Example of AIS Data for One Vessel

This post originally appeared on our Data Blog 

The sample vessel track below shows position broadcasts of the Jin Sheng No.2, a Chinese fishing vessel with mmsi number 413270430. Over three weeks in March of 2015, this vessel steamed from the central Pacific to the coast of Japan, Korea, and China.

413270430_vessel track example

While moving, a vessel broadcasts its position via AIS every 2 to 10 seconds, meaning that this vessel was likely broadcasting thousands of messages per day. These messages can be received either by satellites (the blue dots on the map), or by antennas on the shoreline (the red dots, labeled “terrestrial”).

On the map above, you will see that the blue dots are clustered with sizeable gaps between these clusters. These gaps occur because the satellites aren’t always overhead. You’ll also notice that the frequency of blue dots decreases as the vessel approaches the coast of Asia.

The red dots show where terrestrial antennas recorded the movement of this vessel. You can see that these antennas have a limited reception range and can only “see” so far from shore.

The following chart displays the number of positions per hour for this vessel over the same time period. When satellite reception is good, as in the central Pacific, we record more than 50 positions per hour. But each day there are several hours with no positions.


The number of positions received by satellite per hour decreases as the vessel approaches Asia. The reason is that a satellite can only receive so many AIS messages at once. Close to the coast of Asia, there are so many vessels that each vessel is “seen” less frequently by the overhead satellites.

The terrestrial antennas don’t have the same problem as the satellites, partially because a terrestrial receiver is affected by only the vessels close to it. Terrestrial antennas “see” a much smaller area of ocean and therefore receive fewer signals. A satellite can receive messages from a swath of ocean a few thousand miles wide, which means signals from the entire coast of Asia can interfere with each other.

The upshot is that in parts of the world where there are numerous vessels with AIS, such as in this example near the coast of Asia, satellites provide less reliable coverage of our vessels. Terrestrial antennas, on the other hand, provide a fairly reliable ability to track vessels, but they are limited in their range.

With the current number of satellites in orbit, there will always be gaps in AIS data received from vessels at sea, sometimes of several hours, but the number of satellites in orbit is increasing. This will both increase the number of positions we see in any given hour and reduce the gaps in satellite coverage.

You can see the code used to generate these maps in the original post on our data blog.

There is much more data, code, and description of our process on our data site for researchers and software engineers.

What Can We See When AIS Signals Disappear?

We are often asked about how Global Fishing Watch can be effective when vessel captains can simply turn off their AIS. And our answer has always been, “they have to turn it back on sometime—especially when entering port, and intentional blackouts raise a red flag.” Our recent analysis of fleet activity around the Argentine EEZ is a prime example of how careful analysis allows us to “read between the lines” and quite literally begin to fill in the gaps. Read more

Embedding a Workspace into Your Own Website

A new feature in Global Fishing Watch is the ability to embed a workspace into your own website like this:

Once your workspace is in your web page like this one above, here are the things you can do:

  • Play the timeline: Click on the arrow next to the timeline
  • Move the map view: Click inside the workspace window and drag to move the map.
  • Zoom in or out: Using your mouse pad, scroll wheel or “shift +”and “shift -”  on your keyboard.
  • Go to the live workspace in Global Fishing Watch: Click on the title bar at the top of the workspace.



Select Share in the lower right side of the workspace you would like to embed.


Select “Embed”


Select “Copy.”


Paste code into your website


[Here’s an example of a workspace added to a blog post about the use of geospatial technology and satellites to solve global problems written by someone who heard about Global Fishing Watch through word-of-mouth. ]

AIS for Safety and Tracking: A Brief History

The maritime Automatic Identification System (AIS) is a radio communications system by which vessels continuously broadcast their identity and position over public airwaves using unencrypted VHS radio signals. When it was developed almost 20 years ago, its primary purpose was to increase safety at sea: ships needed a better way to “see” each other and avoid collisions. But authorities also needed a better way to identify vessels and monitor traffic in their waters.

Today, the use of AIS for identifying and tracking vessels around the globe is becoming increasingly more valuable amid growing concerns over international port security and illegal, unreported and unregulated fishing.

In the United States, the history of AIS begins on March 24, 1989, with the oil tanker Exxon Valdez running aground in Alaska’s Prince William Sound. Eleven million gallons of crude oil gushed into the water from the crippled vessel’s slashed hull. It was, at the time, the largest oil spill disaster in U.S. history. In response, the United States Congress passed the Oil Pollution Act (OPA-90), part of which called for the Coast Guard to develop a vessel tracking system for tankers going into Alaska.

The intent, according U.S. Coast Guard Program Analyst Jorge Arroyo, was to improve “situational awareness” for navigators and provide tracking capabilities for shore based Vessel Traffic Services (VTS)—akin to Air Traffic Control. Until then, navigators and shore stations had been dependent on visual navigation, analog radar and voice communications to mitgate collisions. The new system had to be autonomous, continuous and digital—something that could automatically communicate and portray a ship’s location to other ships and to shore-based Vessel Traffic Services without the risk of human error.

The Coast Guard decided on a system that used VHF radio waves. At the same time, tracking systems were being developed and tested around the world. “The British were testing a VHS-based tracking system for ships going in and out of the Dover Strait,” Arroyo says. “The Panama Canal Commission was testing a UHF system, and Swedes were developing another protocol.”

By the mid-90s, the international community realized that it made sense to work together, and a movement began at the International Maritime Organization (IMO) and International Telecommunications Union (ITU) to adopt a single system that could be used worldwide. They decided on the VHS-based AIS system in use today.

Its three primary purposes of were:

1] Collision avoidance

2] Vessel Traffic Service

3] Coastal Surveillance

By 1998, the U.S. Coast Guard had embarked on a plan to modernize their entire vessel tracking service network which relied on voice radio communications and radar. New Orleans was designated as the first port to adopt a primarily AIS-based system. On September 11, 2001, attacks by foreign terrorists on U.S. soil ramped up the efforts, and AIS became an important tool in the Department of Homeland Security defense kit.

Meanwhile, the IMO mandated participating countries to require AIS on certain vessels by 2002 as part of an update to the Safety of Life at Sea Convention. All tankers and passenger vessels equal to or greater than 150 gross tons would be required to carry AIS as well as all other ships of 300 gross tonnage or greater on international voyages and 500 gross tonnage or greater on domestic voyages.

Coast Guard Vessel Traffic Control personnel guide and direct vessels using a bank of monitors including feeds from AIS, VMS, and video cameras. [Photo courtesy: Jorge Arroyo, U.S. Coast Guard]

Different countries have since adopted additional rules. The U.S. now requires commercial vessels of 65 feet or longer to carry AIS within their waters. American flagged vessels of 65 feet or longer must also carry AIS when voyaging in international waters. (Other vessels are also required to carry AIS in U.S. waters, e.g., towing vessels 26 feet or longer and using 600 horsepower or more and vessels certified to carry 150 passengers or more).

Fishing Vessel Exemption

When the regulations were first drawn up in 2003, vocal pushback from industry led the Coast Guard to exempt fishing vessels and passenger vessels with fewer than 150 passengers from the 65-foot threshold. But the exemption was temporary. Last March (2016), the full AIS regulations went into effect, so now AIS is required on all commercial vessels in U.S. waters, including fishing vessels and passenger vessels 65 feet or longer.

The European Union imposed even stricter regulations in 2009, requiring fishing vessels 15 meters (49 feet) or longer to carry AIS. They also explicitly stated that “member States may use AIS data for monitoring and control purposes.” The European Maritime Safety Agency fisheries booklet acknowledges that AIS is beneficial for “marine environment protection,” an increasingly important benefit of a monitoring system broadcast over public airwaves—the feature at the core of Global Fishing Watch operations.

Estimates by researchers in the UK and Canada indicate that as much as 31 percent of the seafood flowing through the global market is illegal, unreported or unregulated (IUU), and a study published in Nature in 2016 found that the United Nations Food and Agriculture Organization has consistently underestimated the amount of fish being taken from the sea by at least 50 percent since 1950. Those are ominous figures in light of studies showing that between 7 and 58 percent of the world’s fish stocks have collapsed or are over exploited and 85 percent are, at a minimum, fished to capacity. If that large spread sounds vague, it’s because there just isn’t enough information about exactly how much fishing is going on.

That’s why it’s crucial to increase our understanding of when and where ocean animals are being harvested. AIS has the power to help us do that. For nearly two decades the Automatic Identification System has surely prevented many collisions and saved countless lives. Using it to track and monitor fishing vessels in every ocean will also allow more accurate measurements of global fish catch and increase transparency and traceability in the fishing industry. Important steps toward ending overfishing and IUU.

A more detailed presentation on the history of AIS can be found here.

An overview of AIS from the US Coast Guard is available here.


86,490 Points on a Map: All Potential Transshipments

5 years of transshipments 86 billion

In early 2017, we released an original report based on analysis of our data that revealed remarkable new insights about what goes on between fishing vessels at sea. The artificial intelligence platform we developed found that over the past five years, there were more than 86,000 potential cases in which fishing vessels transferred their catch to refrigerated cargo ships at sea. The practice is called transshipment, and in many cases it is illegal because it enables the mixing of legal and illegal catch and facilitates slave labor on fishing vessels that don’t need to return to port to drop off their catch. Read more

How to View Multiple Tracks at Once

You can view multiple tracks at once by pinning them to your workspace. Assign different colors to each track to distinguish them from each other.

Here’s how: (Read instructions below or watch a short video here.)

Pin a vessel track to your workspace: Read more

Deciphering Suspicious Behavior: Not Always What It Seems

The first step in catching illegal and unreported fishing activity can feel a little like casting a net over a wide swath of the ocean. There’s going to be a lot of bycatch, because much of what fits in your net isn’t really what you’re after. It takes some background knowledge and often a little investigative work to find the keepers. Sometimes you come up empty handed.

Here are some reasons suspicious-looking behavior by commercial fishing vessels might actually represent perfectly legal activity. Read more

Fishing Fleet Goes Home for the Holidays

‘Tis the season, and even fishers want to be home for the holidays. The flag state filter in Global Fishing Watch allows us to select vessels flagged to a specific country or countries. In the spirit of the season, we decided to use it to see if  a cultural tradition that has nothing to do with fishing can be revealed through fishing vessel behavior. Watch the video to see what we mean, then check it out for yourself by following the links below to the same work space on the Global Fishing Watch map.

Map of the Azores with Spanish fleet activity seen through AIS data.

The same map with individual vessel tracks highlighted 

Taming the Ocean’s Wild West

The high seas are often called the ocean’s Wild West—open territory far from any shoreline or national jurisdiction where the global fishing fleet takes a free-for-all approach to harvesting the world’s shared resources. There’s some truth to that, but there are, in fact, laws intended to manage fishing on the high seas. They’re hard to monitor and even harder to enforce. Read more

What Does an AIS Message Look Like Anyway?

Automatic Identification System (AIS) messages are transmitted over radio waves. The system was designed, in part, so that vessels could “see” the positions of nearby ships on a monitor and avoid collisions. These radio signals are received by satellites and used for many monitoring purposes. Each boat can broadcast a distinct message as often as every two seconds. We receive more than 20 million AIS messages a day.  When we get them, they’re just strings of code. The code below is one AIS message from one boat. Read more

Search for a Vessel on the Global Fishing Watch Map

Know the name or identity of a specific vessel you would like to find on the map? Here’s a step-by-step guide that shows you how to find it. Read more

IUU – Illegal, Unreported, Unregulated Fishing

The term IUU crops up frequently on our site and in discussions of the global fishing industry. It stands for illegal, unreported and unregulated fishing, and it is one of the most serious threats to the sustainability of world fisheries. Read more

What Ports Can Tell Us

Ports provide an important source of information to help us combat Illegal fishing and understand the science and economics of global fisheries. “They serve as the interface between land and sea for fishing vessels,” says Wessley Merten, our data and fisheries analyst at Oceana. “Wherever there’s a port, there’s an interaction. Whether it be offloading catch, exchanging crew, or fueling up to go back out to fish, you have officials and agencies who are theoretically greeting captains, crews and observers.”
Read more

Rendezvous at Sea: What is Transshipping?

In the commercial fishing world, transshipment is the transfer of catch from one vessel to another. During a transshipment, a fishing vessel meets up with a large refrigerated cargo-type ship, known as a “reefer.” They tie up alongside one another and drift while the fishing vessel offloads tons of catch before heading back out to the fishing grounds. Read more

AIS and the Challenges of Tracking Vessels at Sea

At Global Fishing Watch, we hear it all the time: “Tracking commercial fishing vessels from satellites is such a great idea, and it seems so easy!” In fact, we’ve received a few questions from our readers asking us why this isn’t just a simple hack of publicly available data. Read more