Katech AIS Test and Analysis System

What is AIS?

What is AIS?

Universal Automatic Identification System (UAIS) or just AIS is a shipboard transponder system that makes it possible to monitor ships' presence and movement progress from other ships and shore based stations. Ships equipped with AIS continually transmit their position, course, speed and other relevant data on two dedicated VHF frequencies within the allocated marine band. Other AIS equipped ships receive the vessel's information, and are able to identify and track it on a display device such as the electronic navigation chart (ECDIS), radar (ARPA) or dedicated AIS keyboard and display unit (KDU). A more detailed description of AIS operation can be found at the US Coastguard web site or at a dedicated UAIS web site.

Differences between single and dual channel

All AIS transmissions from ships should be broadcast on both radio channels although not simultaneously. Normally, but not exclusively, the transmissions are on alternate channels.

If the receiving location is distant from any shipping activity, then a dual channel receiver will have more available opportunities to decode borderline signals. With a single channel receiver, the signal reporting periods will be approximately halved and it would take correspondingly longer to obtain a full set of ship details, especially if the ships are moored. The more economic single channel receiver will, normally, be perfectly adequate except when an application requires the received information to be as up-to-date as possible.

Since short-term local individual channel interference can occur in some areas, customers may choose which channel receiver to order. A dual channel KATAS receiver may have either channel switched off in software if local interference on one channel is causing temporary reception difficulties.