AIS Aid to Navigation (AtoN) Types: Physical (Real) | Virtual | Synthetic

An AIS AtoN is a digital aid to navigation that is broadcast by an authorized service provider using the AIS Message 21 (Aids-to-navigation report) and is displayed on navigation equipment such as the Electronic Chart Display Information System (ECDIS), radar, or an Integrated Navigation System (INS) (International Maritime Organization (IMO) MSC.1/Circ.1473).

The IMO, considering the mariner’s perspective, has recognized three types of AIS AtoN:

The International Association of Marine Aids to Navigation and Lighthouse (IALA), having assessed the possibilities of AIS technology according to AtoN service providers (national authorities), has proposed the addition of a third type: the Synthetic AIS AtoN.

In accordance with IALA Recommendation A-126, Synthetic AIS AtoN are divided into two types: monitored and predicted.

Because information is transmitted using radio frequencies, each type of AIS AtoN must include Maritime Mobile Service Identity (MMSI) number, which is obtained from Innovation, Science and Economic Development Canada (ISED). As there is currently no recognized symbol for Synthetic AIS AtoN, the distinction between each type is made only by the MMSI number, the AIS AtoN coding parameters (virtual: yes/no), and the positioning mode.

Table 2-1. Summary of MMSI numbers used and Virtual AIS AtoN coding parameters, and the positioning mode used to distinguish AIS AtoN (IALA Recommendation A-126, Ed. 1.5, 2011)
Type of AIS AtoN MMSI (ITU-R M.585-5) AIS AtoN coding parameter Virtual (ITU-R M.1317-4) Positioning Mode
Real 99MID1xxx 0 GPS
Synthetic 99MID1xxx 0 Surveyed
Virtual 99MID6xxx 1 Surveyed

A diamond shaped symbol is used to represent an AIS AtoN on the chart and radar systems that are interfaced with the AIS. Real and Synthetic AIS AtoN use a diamond shape with a solid line, while Virtual AIS AtoN use a dotted line (see Figure 2-1). The AIS AtoN information is displayed when you click the AIS AtoN symbol or move the cursor over it. The displayed description is the only way to distinguish a Real AIS AtoN from a Synthetic or Virtual AIS AtoN (see Figure 2-2).

Table 2-2 Comparison of the types of AIS AtoN according to their association with a physical aid, as well as the origin of the AIS Message 21
Type of AIS AtoN AtoN physically exists Transmission origin of AIS Message 21
Real Yes AIS unit installed on an aid
Monitored Synthetic Yes AIS shore station
Predicted Synthetic Yes AIS shore station or AIS AtoN unit
Virtual No AIS shore station or AIS AtoN unit

Our following products support AIS Virtual & Synthetic functionality:

Maritec Solutions | AIS AtoN Types