The Universal Shipborne Automatic Identification System (AIS) is a system of transponders installed on vessels that transmit over two dedicated digital marine VHF channels. The data is sent from each ship every few seconds and contains position and movement information such as course, speed, latitude, longitude, and rate of turn. Static information about the vessel is sent every few minutes and includes the name, type of ship, length, beam, draft, and other vessel details. Nearly all commercial vessels are mandated to carry AIS transponders, and each year more yachts, launches, and workboats fit AIS equipment.
Automatic Identification System (AIS) uses a transponder or transceiver a GPS and VHF antenna. AIS improves maritime safety, aids in collision avoidance, and helps to identify ships that are not in sight. AIS transmits the ship’s data to other vessels capable of receiving AIS data. The transponder sends the most important ship data, position, speed, and course; this system is used worldwide through standardized message types or telegrams. The data is transmitted twice in case of failure. The data sends over designated VHF Operating frequencies 161.975 MHz (channel A = 2087) and 162.025 MHz (channel B = 2088). There are 4500-time slots available per minute, 2250 per channel—the AIS transceivers alternate one message on channel A next on channel B.
An AIS transponder receives and translates the AIS digital radio signals. It also sends AIS signals, making vessels visible to others with AIS equipment. There are two types of transponders, Class A intended for SOLAS vessels and Class B for fitting on non-SOLAS category vessels. AIS transponders are also known as transceivers in the marine industry.
An AIS receiver operates similarly as a transponder but is a receive-only device. A ship with an AIS receiver will display vessels in the area but not transmit AIS data to other boats in the area.
An AIS display can be a chartplotter, computer, or mobile device if the AIS transponder or receiver is Wi-Fi-enabled via iOS or Android apps. A dedicated display allows critical safety information to always show at a glance and may include additional features.