Frequently Asked Questions

What is AIS?
What information is broadcast?
Why doesn't my yacht show up when there are nearby ships that do?
Why do some ships appear to stop in the sea?
How do I access your site from my boat?
So I can get rid of my radar?
How to contribute AIS data?
What does the number after the AIS Type mean?

With the detailed AIS information you will see a type description (eg Cargo) and a type number (70). The type number is what actually gets broadcast by AIS and this is converted to a description with the following formula:

The first digit represents the general category,

  1. Reserved
  2. Wing In Ground (See this footage on YouTube to see why you would want to get out of their way.)
  3. special category
  4. Hi Speed Craft
  5. special category
  6. Passenger
  7. Cargo
  8. Tanker
  9. Other

While the second digit gives some information as to the cargo

  1. Major Hazard (Haz A)
  2. Hazard (Haz B)
  3. Minor Hazard (Haz C)
  4. Recogniseable Hazard (Haz D)
  5. undefined
  6. undefined
  7. undefined
  8. undefined
  9. undefined

There are also special categories which start with 3 or 5

  1. Fishing
  2. Towing
  3. Towing
  4. Dredger
  5. Dive Vessel
  6. Military Operations
  7. Sailing
  8. Pleasure Craft
  9. Reserved
  10. Reserved
  1. Pilot Vessel
  2. Search and Rescue
  3. Tugs
  4. Port Tenders
  5. Anti-polution
  6. Law enforcement
  7. Local Vessel
  8. Local Vessel
  9. Medical Transport
  10. Special craft

As you can see, the types definitions are a bit vague and have gaps in.Is a RORO ferry a passenger ship carrying cargo or a cargo ship carrying passengers?

Also the operators are not always careful about filling in the numbers so occasionally you might see a ship with type 89. It's probably a tanker of some sort, but there's no definition as to what the 9 means. This is the reason for displaying the type number.

For values over 100, we have:
100: Default Navaid
101: Reference point
102: RACON
103: Offshore Structure
104: Spare
105: Light, without sectors
106: Light, with sectors
107: Leading Light Front
108: Leading Light Rear
109: Beacon, Cardinal N
110: Beacon, Cardinal E
111: Beacon, Cardinal S
112: Beacon, Cardinal W
113: Beacon, Port hand
114: Beacon, Starboard hand
115: Beacon, Preferred Channel port hand
116: Beacon, Preferred Channel starboard hand
117: Beacon, Isolated danger
118: Beacon, Safe water
119: Beacon, Special mark
120: Cardinal Mark N
121: Cardinal Mark E
122: Cardinal Mark S
123: Cardinal Mark W
124: Port hand Mark
125: Starboard hand Mark
126: Preferred Channel Port hand
127: Preferred Channel Starboard hand
128: Isolated danger
129: Safe Water
130: Manned VTS / Special Mark
131: Light Vessel / LANBY


Errors in AIS