Automatic Identification Systems (AIS)
What is an Automatic Identification System (AIS)?
AIS, or Automatic Identification Systems, provide a ship's location, speed, heading, and other identification data to maritime authorities and other ships using AIS transponders, which can be employed to trace and track a ship's past and current activity.
AIS systems were first created as a collision avoidance measure for vessels at sea. However, they are now used for monitoring and intelligence purposes, helping maritime authorities regulate shipping and trade activities.
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Today, almost all maritime vessels are equipped with AIS transponders. AIS systems help ensure sanctions compliance, legal and sustainable fishing operations, and many other things related to maritime activity.
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Although most operable vessels use AIS, the tracking systems can easily be turned off or manipulated - creating an opportunity for nefarious individuals to achieve unlawful goals by altering or hiding their AIS position and operating undetected. While some AIS circumvention methods are complex and require detailed planning, turning off an AIS transponder (Dark Shipping) is extremely simple and easy to execute.
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The above image displays an example of an "AIS Darkness" event. The solid black lines represent the locations where the ship was transmitting its position on AIS, while the red line indicates gaps in AIS transmission.
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Why Would a Ship Turn its AIS Transponder Off?
While there are some legitimate and lawful reasons for turning off a ship's AIS, think ship maintenance or inactivity, it is unlikely that there is a valid reason for doing so while in transit. Most incidences of AIS darkness at sea are a sign of foul play - most commonly used to avoid sanctions enforcement or pass through prohibited waters. By circumventing sanctioned waters, ships like large oil tankers can make massive profits by loading or offloading cheap sanctioned crude from places like Venezuela or Iran and passing it off as legitimate, unsanctioned cargo. ​
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RF Geolocation: How to Track a Vessel With Its AIS Off
Tracking a vessel with no AIS data can be challenging, depending on the length of an AIS Darkness event. The longer the outage, the more possibilities there are for where the ship could have traveled. ​One of the most effective strategies for locating and tracking vessels not broadcasting their AIS or GNSS position is to use satellite-based Radio Frequency (RF) geolocation.
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Space-as-a-service providers use satellite clusters (groups of 3-4 satellites operating in formation in LEO) to capture RF signals emitted from vessels. From there, the satellites use timing and location data to pinpoint the ship’s precise location on the Earth's surface.
Even if the ship is not broadcasting AIS or GNSS signals, RF geolocation can still provide highly accurate position data by triangulating the RF data from the vessel.​ This capability significantly reduces the uncertainty surrounding dark shipping events and enables authorities to track vessels with a level of precision that AIS or radar alone cannot match.​
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AIS Spoofing: Position Manipulation
While deliberate periods of AIS darkness remain the most common method to conduct illicit activity, other methods are evolving and becoming more commonplace.
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One of the more complex methods used is referred to as "AIS Spoofing." AIS spoofing involves using additional equipment to manipulate a ship's AIS tracks - continuously plotting points in identical positions or manufacturing fake transits altogether. It is worth noting that periods of AIS spoofing may also involve periods of AIS outages, as each method of AIS manipulation is not exclusive and is often used in conjunction with one another.
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The above image displays two obvious examples of a ship attempting to manipulate its AIS position.
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If a ship were anchored and not moving, you would expect to see a circle or semi-circle pattern, with only slight changes in speed as the wind and waves impact the ship. In the images above, the ships record consistent speeds with almost no variation - a telltale sign of AIS manipulation.
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The above image displays two examples of a ship's AIS position while at anchor.
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The left image is an example of legitimate AIS data from an anchor position, while the image on the right displays an AIS spoofing attempt. We can immediately see that the legitimate anchor position has subsequent AIS tracks in a natural flow, with the wind and waves slowly pushing the ship from side to side. The spoofed position, however, has no natural effects present - with AIS data plotted on opposite sides of the anchor position.
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Once again, RF data can help authorities confirm suspected instances of AIS spoofing - using the same 3-4 satellite strategy as described above.
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The Future of AIS
As long as ships are tracked with AIS data, certain groups and individuals will continue implementing AIS manipulation techniques to hide their actions. Due to the ease and accessibility of AIS manipulation methods, going AIS dark will likely remain the "go-to" way of obscuring a ship's position. Fortunately, we can counter these efforts by incorporating RF datasets, open-source information, and satellite imagery to accurately track a ship's movements.
