Automatic Identification System

The Automatic Identification System (AIS) was originally developed to aid the Vessel Traffic Services (VTS) by use of a VHF transponder working on Digital Selective Call (DSC) at VHF CH70, and is still in use along the UK coastal areas and others. Some time later the IMO developed a Universal AIS using the new sophisticated technology called Self-Organized Time Division Multiple Access (SOTDMA) based on a VHF Data Link (VDL). The system operates in three modes – autonomous (continuous operation in all areas), assigned (data transmission interval remotely controlled by authority in traffic monitoring service) and polled (in response to interrogation from a ship or authority). It is synchronized with GPS time to avoid conflict among multiple users (IMO minimum 2000 reports per minute and IEC requires 4500 reports on two channels). The VHF channels 87B and 88B are commonly used and in addition there are local AIS frequencies. Shipborne AIS transponders exchange various data as specified by the IMO and ITU on either frequency automatically set up by the frequency management telecommand received by the DSC receiver on ship.

Introduction 3

1 Applications and limitations 4

1.1 Collision avoidance 4

1.2 Vessel traffic services 4

1.3 Aids to navigation 4

1.4 Search and rescue 5

1.5 Accident Investigation 5

1.6 Binary messages 5

1.7 Computing and networking 5

1.8 AIS data on the Internet 6

1.9 Range limitations and space-based tracking 6

1.10 Type Testing and Approval 7

2 How AIS works 8

2.1 Basic overview 8

2.2 Message Types 9

2.3 Detailed description: Class A units 9

2.3.1 Broadcast information 11

2.4 Detailed description: Class B units 12

2.4.1 Message 14: Safety Related Message

2.4.2 Message 18: Standard Class B CS Position Report

2.4.3 Message 19: Extended Class B Equipment Position Report

2.4.4 Message 24: Class B CS Static Data Report

2.5 Detailed description: AIS Receivers 13

Summary 14

Attachement 16

Vocabulary 20