Frequently Asked Questions
About the Marine Traffic project
This web site is part of an open, community-based project. It is dedicated in collecting and presenting data which are exploited in research areas, such as but not limited to the following:
- Study of marine telecommunications in respect of efficiency and propagation parameters
- Simulation of vessel movements in order to contribute to the safety of navigation and to cope with critical incidents
- Interactive information systems design
- Design of databases providing real-time information
- Statistical processing of ports traffic with applications in operational research
- Design of models for the spotting of the origin of a pollution
- Design of efficient algorithms for sea path evaluation and for determining the estimated time of ship arrivals
- Correlation of the collected information with weather data
- Cooperation with Institutes dedicated in the protection of the environment
It provides free real-time information to the public, about ship movements and ports, mainly across the coast-lines of many countries around the world. The initial data collection is based on the Automatic Identification System (AIS). We are constantly looking for partners to take part in the community. They will have to install an AIS receiver and share the data of their area with us, in order to cover more areas and ports around the world.
How are vessel positions recorded?
The system is based on AIS (Automatic Identification System). As from December 2004, the International Maritime Organization (IMO) requires all vessels over 299GT to carry an AIS transponder on board, which transmits their position, speed and course, among some other static information, such as vessel’s name, dimensions and voyage details.
What is AIS?
AIS is initially intended to help ships avoid collisions, as well as assisting port authorities to better control sea traffic. AIS transponders on board vessels include a GPS (Global Positioning System) receiver, which collects position and movement details. It includes also a VHF transmitter, which transmits periodically this information on two VHF channels (frequencies 161.975 MHz and 162.025 MHz – old VHF channels 87 & 88) and make this data available to the public domain. Other vessels or base stations are able to receive this information, process it using special software and display vessels locations on a chart plotter or on a computer.
What is the range of AIS?Normally, vessels with an AIS receiver connected to an external antenna placed on 15 meters above sea level, will receive AIS information within a range of 15-20 nautical miles. Base stations at a higher elevation, may extend the range up to 40-60 NM, even behind remote mountains, depending on elevation, antenna type, obstacles around antenna and weather conditions. The most important factor for better reception is the elevation of the base station antenna. The higher, the better. We have seen vessels 200 NM away, with a small portable antenna placed on an island mountain on 700 meters altitude! Our base stations cover fully a range of 40 miles and periodically receive information from some more distant vessels.
How is the data collected?
Our base stations are equipped with an AIS receiver, a PC and an Internet connection. The AIS unit receives data, which are processed by simple software on the PC and then sent to a central database by means of a ‘web service’. This software is free for anyone interested, under a GNU license. (Read section 'Cover your Area' for more information on how to install your own AIS base station).
Data received by the AIS unit are encoded in NMEA sentences (64-bit plain text). A sample is shown below:
Messages include the following three basic types:
- Dynamic Information, such as vessel’s position, speed, current status, course and rate of turn.
- Static Information, such as vessel’ name, IMO number, MMSI number, dimensions.
- Voyage-specific Information, such as destination, ETA and draught.
How is this information displayed on this site?
The central database receives and processes a large amount of data and stores the most important part of it. It also includes port and area geographic information, vessel photos and other information. Vessels current positions and/or tracks are displayed on a map, using the Google’s map API. Position history, vessel’s details, port conditions and statistics are searchable through our web pages.
How often is the data updated?
Data received are uploaded in the database in real time and therefore they are immediately available on the map and on other pages. However, several positions shown on map may be not continuously refreshed (e.g. when a ship goes out of range). Vessel positions shown on map may be up to 1 hour old. Please note also that map web page is only periodically refreshed or whenever the ‘Refresh now’ link is pressed manually.
Why is my vessel not visible?
The MarineTraffic system does not cover all the seas of the world, but only specific coastal areas where a land-based AIS receiver is installed. Vessels appearing on the live map are equipped with an operational AIS transponder and they sail within the reception range of an AIS receiver installed on the land. Possible reasons for a vessel's position not picked up and displayed on the live map are:
- The vessel is not equipped with an AIS transponder or the transponder is not operational or the transponder is not properly working
- The vessel sails in an area where no nearby AIS receiving station exists
- The transmission power of the vessel's AIS transponder is not enough in order for a land-based station to receive the signals. This depends on the type of the transponder, the type and the height of the antenna and the quality of the cabling
- Especially for vessels equipped with a Class-B AIS transponder, the transmission power of AIS signals is much lower than the power of a Class-A transponder and therefore the reception range in much more restricted
- The AIS transponder of the vessel is not configured to transmit the correct information (e.g. MMSI number, ship's name etc.)
Why do the map icons refresh slowly sometimes?
Partial or strange data appear from time to time. Why is that?
The system may receive positions for a vessel, which has not yet transmitted its static information (name, dimensions etc.). This happens because static vessel’s information is transmitted more rarely than positions. In this case, the MMSI number of the vessel (e.g. 239923000) will appear instead of its name. There is also a small possibility of wrong or garbled recorded data. This happens due to the following reasons:
- Malfunction of the AIS transponder of the vessel,
- Errors of the Global Positioning System (GPS) and
- Neglect of the vessel's crew to configure correctly the information transmitted by the AIS transponder (this refers to the static information, such as the vessel's name, type and dimensions, as well as the destination and the ETA)
How the vessel's crew can help?
The system is exclusively based on the information received by the vessels, as they are transmitted by their AIS tranponders. Consequently, the correct configuration of the AIS transponders by the crew is very important! Specifically, the officer who is responsible for the operation of the AIS transponder can significantly help in the correct presentation of the vessel's information, by taking care of the following:
- Correct updating and checking of the 'Static Information' which are recorded in the AIS unit. These include: Vessel's Name, Vessel's Type, Vessel's Dimensions, IMO and MMSI numbers, Relative position of AIS unit.
- Correct updating of the 'Voyage Information', i.e. the Destination, ETA and Draught, before each departure. When this information is correct, the vessel will appear in the 'Expected Arrivals' for each port and an estimation of the time of arrival will given, for all the interested parties. A single port must be entered each time and any additional information (such as country or multiple ports) must be avoided.
What notation is used for vessels?
Moving vessels are displayed as ship icons pointing to the specified direction (heading). Ships that are not moving (or their speed is less than 0.5 knots) anchored or moored are displayed as small squares. Vessel icons and tracks are colored according to their type (cargo, tanker, passenger, etc.) as explained in the page showing the live map.
Can we expand the coverage to include more areas?
Our system can be expanded to cover any area worldwide. Anyone can install a VHF antenna, an AIS receiver and start immediately sending and seeing data on the map, through a PC and a simple Internet connection. For anyone wishing to cover an area in our map, we will put an acknowledgement in our pages, a link to her/his personal or company site or any other reference requested. Most important, you will get your area fully covered with map positions, vessel tracks, port information, historical data search and every other functionality offered through our web site. You may also put a live map of your area in your own web site. See section ‘Cover your Area’ for details on how to build your own AIS base station.
How can I see the position of my boat on the map?
If you own a private boat sailing within the areas covered by MarineTraffic, you may install an AIS transponder on board, in order to record its positions on our real-time map. The installation of an AIS transponder on small vessels is optional and you are allowed to use a ‘CLASS B’ transponder. Class B transponders are cheaper than ‘Class A’ AIS transponders and they are addressed to the non SOLAS compliant vessels (e.g. small leisure or fishing vessels, less than 300 GT). The price of a Class B transponder varies from 700 to 2000 euros.
Alternatively, you may use the iAIS application on your smart phone (iPhone/iPad or Android) on board to report the position of your vessel directly to MarineTraffic, without the requirement to operate an AIS transponder.
There are at least 5 different methods for reporting your own position to MarineTraffic. Read more...
Can the web-published information be used to enhance safety at sea?
This is not the intention of this system. Data provided can only be used by Internet users for informational reasons only and they are by no means related to safety of navigation. Information provided may be incomplete, obsolete or contain errors and cannot substitute the on-board safety equipment and of course the good seamanship.
Although marinetraffic.com is not intended to be used a safety tool, there are many cases where making your position widely known could enhance your safety at sea. Making your position known to the public may be complementary to the official means of distress reporting such as EPIRB or DSC radio and may help in Search & Rescue procedures where the position of the vessel cannot be acquired by other means.