Aids to Navigation

The MariWeb™AIS network can be used as a low cost method of monitoring fixed and floating Aids to Navigation [AtoN].  IALA has defined a number of methods of achieving this as follows:

There are various IALA supported AIS based solutions that range from having a full featured AtoN AIS fitted to the buoy through to using low cost telemetry links and transmitting data via an AIS base station back into the maritime environment being managed. There are five possible approaches to this issue:

• Type 1 AtoN AIS
• Type 2 AtoN AIS
• Type 3 AtoN AIS
• Synthetic AtoN AIS
• Virtual AtoN AIS

The first three of these ‘real’ AtoN solutions are described immediately below. Relevant regulatory details can be obtained in the IALA A-126 Recommendation.

Type 1 AtoN AIS

The Type 1 AIS AtoN Station is a transmit-only station, operating in FATDMA mode. Hence the slots used by the Type 1 AIS AtoN Station need to be reserved.

This is the simplest type of AIS AtoN station, likely to have low cost and power consumption.

Type 2 AtoN AIS

The Type 2 AIS AtoN Station is similar to a Type 1, but has, in addition, an AIS receiver of limited capability operating on a single AIS channel. This receiver allows the Type 2 Station to be remotely configured and controlled via the AIS VDL.

Type 3 AtoN AIS

The Type 3 AIS AtoN Station is more complex than the Type 1 and Type 2, and contains two AIS receiving processes that allow it to participate fully on the AIS VDL. This means that in addition to FATDMA, the Type 3 station can function in RATDMA mode.

The Type 3 station is therefore capable of:

• Autonomous operation, not requiring slot reservations.
• Receiving and relaying AIS messages.
• Relaying AIS messages related to search and rescue.
• Indirect synchronisation, using its receiving processes.

The Synthetic and Virtual options are dealt with in the next section.

MariWeb™ Synthetic and Virtual AtoN

For practical or economic reasons it may not be appropriate to fit a ‘real’ AIS to an AtoN. In this case, the ‘Synthetic’ or ‘Virtual’ AIS approach may be taken. There are 2 types of Synthetic AIS AtoN and one Virtual AIS AtoN. The Synthetic AtoN types are:

• Monitored Synthetic AIS AtoN.
• Predicted Synthetic AIS AtoN.

These solutions require that an AIS base station be available in the monitored area to transmit the synthetic or virtual buoy information.

Monitored Synthetic AIS AtoN

A ‘Monitored Synthetic AIS AtoN’ is transmitted as an ITU-R.M1371-3 Message 21 from an AIS Station that is located remotely from the AtoN. The AtoN physically exists and there is a communication link between the AIS Station and the AtoN. The communication between the AtoN and AIS confirms the location and status of the AtoN.

Predicted Synthetic AIS AtoN

A ‘Predicted Synthetic AIS AtoN’ is transmitted as an ITU-R.M1371-3 Message 21 from an AIS Station that is located remotely from the AtoN. The AtoN physically exists but the AtoN is not monitored to confirm its location or status.

Only a Monitored Synthetic AIS AtoN ensures the integrity of the floating AtoN, therefore the use of a Predicted Synthetic AIS AtoN is not recommended for use on floating AtoN. Predicted Synthetic AIS AtoN broadcasts for fixed AtoNs is acceptable as the location will not change, but the status of the AtoN is not verified.

Virtual AtoN

A “Virtual AIS AtoN” is transmitted as an ITU-R.M1371-3 Message 21 for an AtoN that does not physically exist. It may be appropriate to create a virtual AtoN, where no physical AtoN exists. In this case the symbol would appear on the display for a specified location, even though there is no physical AtoN. A nearby AIS base station or AtoN station could broadcast this message. The flag in an ITU-R.M1371-3 Message 21 would clearly identify this as a Virtual AIS AtoN. An example of where Virtual AIS AtoN could be useful is the marking of hazards to navigation on a temporary basis (see IALA Recommendation 0-133, Emergency Wreck Marking), until a more permanent AtoN can be established.

MariWeb™ Applications for an AtoN network

• Central Data Server [CDS] along with the Physical Shore Station [PSS] Base Station Controller  [BSC]
• Electronic Chart Server [ECS] and Human Machine Interface[HMI]
• The MariWeb™ Event Manager [MEM]
• The MariWeb™ Archive Server [MAS]
• Network Monitoring System [NMS]
• The MariWeb™ Chart Server [MCS]
• The various MariWeb™ tabular and graphical reporting modules

MariWeb™ continues to be developed and due to its modular design, new modules can be designed and included and existing modules can be combined to satisfy the requirements of the customer.