[eli5] How vessel tracking work ? Who provide the data to them ?
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There are many ways that vessel tracking companies collect data on ship movements. One common method is through the use of Automatic Identification System (AIS) data. AIS is a system that is required by most large commercial vessels to broadcast their position, course, and speed periodically. This data can be picked up by AIS receivers, which are then used to track ship movements. Other methods for collecting vessel tracking data include using satellite imagery, radar, and human observers.
If you are talking about ship tracking there is a system called Automatic Identification System which is required to be mounted to all larger ships. This system broadcasts information about the vessel such as its name, registration number, status, destination, position and speed over VHF radio. The purpose of this is so that other ships in the area can receive this information and make navigation decisions based on it. You get a lot more information then with a radar and it is much cheaper and reliable.
But since this information is broadcast in clear anyone within visual range of the ship can pick up these broadcasts. It can then be logged and shared with others. The receivers are very cheap so you can have a lot of them in coastal areas. And for years now a lot of satellites have been fitted with such receivers as well which extends coverage to the entire globe.
Aircraft have a very similar system called ADS-B. It works on the same principles but use different frequencies and different type of data.
Automatic Information System (AIS) is a system to be fitted on most commercial vessels (300 gross tonnes or more for international voyages, 500 gross tonnes or more for non-international voyages and all passenger vessels). (These are class A, class B are for pleasure crafts etc)
The system works on the VHF band, basically meaning any other system in the line of sight will get my information. For a class A system this include GPS, speed, course, number of persons onboard, destination, dimension of vessel including draft, call sign, mmsi, status etc)
Web trackers like marine traffic have antennas around the world to pick up the signals and make them available on there webpage for tracking and spotting from home.
Another option is LRIT (LongRange Identification and Tracking). This contains though much less information, mainly used for tracking cross ocean passages for SAR purpose.
Lastly, in modern times, the vessels are beginning to be ever connected via satellite internet to shore functions. This information is though typically only for in-house use and not available for others. But also here is GPS position etc included in the data
Source: navigational officer for a major container carrier
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