AIS provides identification of targets together with the static and dynamic information Mariners should, use this information with caution noting the following important points:

Collision avoidance must be carried out in strict compliance with the COLREGs. There is NO provision in the COLREGs for use of AIS information therefore decisions should be taken based primarily on visual and/or radar information.

The use of VHF to discuss action to take between approaching ships is fraught with danger and still discouraged. Decisions on collision avoidance should be made strictly according to the COLREGs


Not all ships will be fitted with AIS, particularly small craft and fishing boats. Other floating objects which may give a radar echo will not be detected by AIS.

AIS positions are derived from the target’s GNSS position. (GNSS = Global Navigation Satellite System, usually GPS). This may not coincide with the radar target.

Faulty data input to AIS could lead to incorrect or misleading information being displayed on other vessels. Mariners should remember that information derived from radar plots relies solely upon the data measured by the own-ship’s radar and provides an accurate measurement of the target’s relative course and speed, which is the most important factor in deciding upon action to avoid collision. Existing ships of less than 500 gt. Which are not required to fit a gyro compass are unlikely to transmit heading information.


AIS is intended to enhance: safety of life at sea; the safety and efficiency of navigation; and the protection of the marine environment. SOLAS regulation V/19 requires that AIS exchange data ship-to-ship and with shore-based facilities. Therefore, the purpose of AIS is to help identify vessels; assist in target tracking; simplify information exchange (e.g. reduce verbal mandatory ship reporting); and provide additional information to assist situation awareness. In general, data received via AIS will improve the quality of the information available to the OOW, whether at a shore surveillance station or on board a ship. AIS should become a useful source of supplementary information to that derived from navigational systems (including radar) and therefore an important ‘tool’ in enhancing situation awareness of traffic confronting users.

  • See MGN 324
  • ColRegs Rule 7
  • SOLAS Ch V Annexe 17