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.

pos_per_hour413270430

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.

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.

HERE’S HOW YOU DO IT:

STEP 1

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

STEP 2

Select “Embed”

STEP 3

Select “Copy.”

STEP 4

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. ]

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 

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