What Is AIS? Understanding the Vessel Tracking System
If you’ve ever wondered how apps like MarineRadar or others show ships moving in real time, the answer is simple: AIS, or Automatic Identification System.
But what is AIS, and why is it one of the most important marine safety systems in the world today?
In this blog, we’ll break down the Marine Vessel Tracking System in the simplest, most effective way.
What Is AIS?
AIS stands for Automatic Identification System. It is like a name tag and GPS tracker that ships use to tell others who they are and where they’re going. According to official definitions, AIS transponders are designed to automatically provide a ship’s position, identification, and other information to other vessels and coastal authorities.
The Automatic Identification System helps ships share the following:
- Where they are (GPS position)
- Where they are going (destination)
- How fast they’re moving (speed)
- Who they are (ship name)
- What type of vessel they are (cargo, tanker, ferry, etc.)
- Safety status (e.g., at anchor, underway)
In simple terms, the Automatic Identification System is a tiny radio beacon on the ship. It broadcasts the ship’s information out into the sea.
How Does AIS Work?
The Automatic Identification System works with a few key parts:
Transponder on the Ship:
Each ship has a small AIS transmitter. It sends out radio signals in the VHF band every few seconds. (VHF is just a fancy way of saying “a type of radio frequency” used by ships.)VHF Radio Band:
The signals travel through the air like a radio broadcast. The Automatic Identification System uses a special system (SOTDMA) to handle multiple ships simultaneously.Receiving Stations:
These signals pick up:- Coastline towers (terrestrial stations) are located near the shore.
- Satellite receivers orbiting the Earth.
- Other ships in the area.
- Every few seconds, your ship’s AIS sends out a “hello” with all its info, and those stations pick it up.
Data Sharing:
The received automatic identification system signals are forwarded to various systems:- Ship traffic services (like digital radars)
- Coastal authorities (for port management)
- Tracking websites and apps (like MarineRadar)
MarineRadar’s live map collects all this automatic identification system data from around the world and displays ships moving on it in real time. This lets you see thousands of ships sailing around the world, as if you were watching a movie.
What data does an automatic identification system transmit?
An AIS broadcast includes a lot of useful information. For each ship, the automatic identification system typically sends the following:
- MMSI number (a unique 9-digit maritime ID)
- Vessel name and IMO number
- Ship type (e.g., cargo, tanker, passenger)
- Position (latitude and longitude)
- Speed (over ground)
- Course (heading)
- Destination port and ETA (Estimated Time of Arrival)
- Navigation status (e.g. underway, anchored)
The IMO and USCG confirm that automatic identification system broadcasts include identity, type, position, course, speed, and other safety-related information.
Who Uses Automatic Identification System?
Many people and organizations rely on automatic identification system:
- Commercial Ships: Cargo ships, tankers, and passenger liners are required by law (for big ships) to have AIS transponders. This helps them avoid collisions and stay visible.
- Coast Guard and Navies: They monitor the automatic identification system to keep track of vessels and ensure safety at sea.
- Port Authorities: They use an automatic identification system to manage traffic in busy harbours, knowing which ships are arriving or leaving.
- Fishing Boats and Recreational Vessels: Smaller boats often carry Class B AIS (a simpler version) so they can be seen by others and follow fishing rules.
- Ship Tracking Apps: Platforms like MarineRadar use the automatic identification system to show live ship locations to hobbyists, researchers, and anyone interested.
So whether it’s a giant cargo ship or a small yacht, many vessels wear AIS like a digital name tag.
How MarineRadar Uses Automatic Identification System Data
MarineRadar gathers AIS (Automatic Identification System) signals from around the globe to power its live map and features. The app/website uses a hybrid automatic identification system: it combines signals from land-based receivers and satellites. This means MarineRadar can track ships near the coast and in the middle of the ocean.
On MarineRadar, you can:
- See live ship positions on the map.
- Click a ship to view its details (name, speed, and ETA).
- Monitor ship traffic density in an area.
- View arrival and departure times for ports.
- Track different types of vessels (tanker, fishing, etc.).
Every time a ship sends its AIS broadcast, MarineRadar updates the map in real time.
Class A vs Class B AIS
There are two main classes of AIS: Class A and Class B. The difference is mainly in who uses them:
AIS Type | Used By | Power | Update Frequency | Best For |
Class A | Cargo ships, tankers, passenger ships | High | Fast | Commercial vessels |
Class B | Small boats, yachts, and fishing boats | Low | Slower | Recreational boaters |
Class A:
This is the bigger, more powerful Automatic Identification System. It’s required for commercial ships (like cargo and passenger ships). It broadcasts frequently and includes a lot of data.Class B:
This version is for smaller boats (like private yachts and fishing boats). It sends updates less often and has slightly less information. Class B is still very useful for visibility and safety.
Both classes help see and avoid each other. On MarineRadar, you can track both Class A and Class B vessels.
Automatic Identification System Limitations
The Automatic Identification System is very useful, but it has a few limitations:
- Coverage Gaps: Terrestrial AIS coverage extends only about 40 miles offshore. In the open ocean, you need satellite AIS to cover the gaps.
- Signal Congestion: In very busy areas, too many ships may try to broadcast simultaneously, causing delays.
- Spoofing/Jamming: Like any radio signal, the automatic identification system can be jammed or faked by bad actors. (New rules are being made to reduce these risks.)
- Power/Technical Difficulties: A ship’s AIS can fail or be turned off (sometimes illegally). Such failures can leave gaps in tracking.
Combined with radar and other systems, it provides the most complete picture of marine traffic.
How AIS Improves Safety
The Automatic Identification System has made the seas much safer:
- Collision Avoidance: Ships see each other on their screens even in fog or at night, greatly reducing crashes.
- Rescue Help: In emergencies, rescue teams use automatic identification system signals to locate vessels faster.
- Port Efficiency: Ports coordinate traffic via AIS, resulting in smoother cargo operations.
- Environmental Protection: By monitoring the Automatic Identification System, authorities can detect if a ship strays into sensitive areas and respond quickly.
Without AIS, marine tracking apps and navigation systems would have no way of knowing where most ships are. The Automatic Identification System has been called “one of the most important inventions in modern navigation” for this reason.
Conclusion
The Automatic Identification System (AIS) is a GPS-like tracking system for ships. It automatically broadcasts each vessel’s identity, position, speed, and more. Apps like MarineRadar collect this data to show ships moving live on a map.
Because of AIS, the ocean is more connected and safer than ever. Opening the MarineRadar and seeing ships sailing across the screen makes the marine world visible.
Download Marine Radar: Vessel Tracker from the Google Play Store or App Store today and experience real-time ship tracking.