AIS explained

AIS stands for Automatic Identification System. This system automatically transmits and receives important ship data, such as position, course and speed. Both static and dynamic information is combined and broadcast via an AIS transponder (or AIS transceiver). The built-in Very High Frequency (VHF) transmitter transmits this data, after which AIS receivers receive and display it. This creates a real-time picture of vessel traffic, greatly enhancing safety at sea and on inland waterways.

Content: most frequently asked questions about AIS

AIS receiver or transponder?
Which AIS solution should I choose?
What is the difference between AIS Class A and Class B?
What does 2 watts and 5 watts mean?
Why an AIS transponder with Wi-Fi?
Do I need permission to use AIS?
What is ATIS and MMSI, and when do I need which?
When do you need what?
Is AIS mandatory?
Which countries do require AIS for pleasure craft?
Do I need a separate antenna for AIS?
How far does an AIS signal reach on average?
Which apps or software work well with AIS?
How reliable is AIS in bad weather or crowded areas?
What is the difference between terrestrial AIS and satellite AIS?
What should I do if I sell my vessel - will my MMSI remain valid?
Do I always turn on my AIS even when I am lying still?
Can I temporarily turn off my AIS (e.g. for privacy reasons)?
Buy cheap AIS?

AIS receiver or transponder?

A AIS receiver (receiver) only receives AIS data from other ships. A AIS transponder (transceiver) also transmits your own data.

Nowadays, you can also view AIS information online via websites and apps such as MarineTraffic, VesselFinder or Waterkaarten. This information is based on data from AIS receivers on land or via satellites.

With an AIS receiver on board, you receive the data directly via your VHF antenna, without delay, within the range of your antenna. With a transponder also broadcast your own ship data, so other ships can see you.

Note: apps like Waterkaarten can share your position via internet with other users of the same app. But this is not AIS: ships with a real AIS receiver or plotter will then not see you, unless you also have an AIS transponder on board.

Which AIS solution should I choose?

We recommend a AIS transponder on, so you not only see other ships, but they see you too. Receiving (online) AIS via an app is fine for a sloop or day trips, but if you sail longer trips with a sailing or motor boat, a real transponder is much safer.

Although AIS is not mandatory for ships under 20 metres in the Netherlands, it is strongly recommended - especially on busy waterways or in poor visibility. Transponders are also becoming increasingly affordable and are a valuable investment in safety.

What is the difference between AIS Class A and Class B?

Class A is mandatory for commercial shipping and seagoing vessels covered by the SOLAS Convention.
Class B is intended for pleasure craft and small commercial vessels.

What does 2 watts and 5 watts mean?

2-watt transponders usually use CS (Carrier Sense) technology. These transponders are covered by AIS Class B (CS-B).

They "listen" if the channel is free before transmitting (Carrier Sense).
This technique is simpler and cheaper, but can lead to delays when the canal is busy (e.g. in ports).

5-watt transponders use SOTDMA (Self-Organised Time Division Multiple Access) technique.

This is the same technology used in AIS class A transponders (mandatory on commercial vessels).
These transponders themselves reserve a time slot for transmitting data, allowing for no waiting or delays is.
This version of class B is also called class B+ or class B SOTDMA named.

Why an AIS transponder with Wi-Fi?

An AIS transponder with wifi (or a connection via a wifi multiplexer) sends AIS data wirelessly to your tablet, smartphone or laptop. So you see AIS directly on your nav app, without cables.
Some models also have Bluetooth, which allows you to program settings wirelessly.

GPS data
By default, we set our AIS transponders to transmit not only AIS data, but also GPS position wirelessly via Wi-Fi. This is especially useful for iPads without built-in GPS (the WiFi-only models). Thanks to this setting, you can still simply see your exact position in your navigation app, without extra cables or accessories - and with the accuracy of a full-fledged GPS receiver.

NEW! AIS Transponder with WiFi - super cheap

Do I need permission to use AIS?

AIS receiver: No. You do not need a licence or certificate. The device does not transmit, it only listens.
AIS transponder: Yes. You have a marine basic certificate needed and a MMSI number, to be requested from the National Digital Infrastructure Inspectorate (RDI, formerly Agentschap Telecom). Because the transponder transmits VHF signals, it is considered transmitting equipment.

What is ATIS and MMSI, and when do I need which?

ATIS (Automatic Transmitter Identification System) is mandatory on most inland waterways in Europe. A unique identifier is automatically sent with each transmission. Only required for transmitting equipment (such as marine radio) on inland water.
MMSI (Maritime Mobile Service Identity) is a unique number you need for digital communication via AIS or VHF radio with DSC (Digital Selective Calling).

When do you need what?

Use	ATIS	MMSI	Certificate
Listen only (AIS receiver)	No	No	No
VHF radio	Yes	No	Yes
AIS transponder	No	Yes	Yes

Note that for each transmitting device, you need at least the Basic certificate in marine navigation needed.

Is AIS mandatory?

For recreational craft < 20 metres AIS is not mandatory in the Netherlands, but is recommended.
AIS is mandatory in the following cases:

Commercial shipping on inland waterways (e.g. cargo ships, passenger ships)
Maritime shipping: commercial vessels >300 GT (SOLAS rules)
Pleasure craft >20 metres on certain waterways, such as the Rhine

Other countries and territories
Additional rules apply in some countries (such as Germany and Belgium) - including for smaller pleasure craft on busy waterways. In the port of Antwerp, AIS is mandatory. So always check the rules of the area where you are sailing.

Which countries do require AIS for pleasure craft?

In the Netherlands, AIS is only mandatory for pleasure craft >20 metres on certain waterways (such as the Rhine). Other countries sometimes have stricter rules, for example:

Germany: AIS mandatory for pleasure craft >20 metres, and on some busy waterways also for smaller vessels.
Belgium: AIS mandatory for pleasure craft >15 metres or with a DSC marine radio.
Austria and Switzerland: AIS mandatory on certain lakes and rivers.
France: No general obligation yet, but this may change in the future.

Always check the current regulations of the country or sailing area you are going to. For example, AIS is mandatory in the port of Antwerp.

Do I need a separate antenna for AIS?

An AIS transponder has a VHF antenna needed. You can use a separate antenna places, but you can also place a antenna splitter use to share your VHF antenna with the AIS. Note that you will then need a active splitter use one that is especially suitable for transmitting as well as receiving, otherwise you may damage your equipment.

How far does an AIS signal reach on average?

The range of AIS depends on the height of your antenna and that of other ships. On average, the range on inland waterways and along the coast is about 8 to 20 nautical miles (15-37 km). On the open sea, with a high mast or antenna, this can be as high as 30 miles or more. Satellite AIS can reach even further, but it works differently.

Which apps or software work well with AIS?

Popular apps that can display AIS data (with a linked transponder or NMEA data via wifi/bluetooth) include:

Read about our unique partnership with Waterkaarten

For online AIS display (based on land stations and satellites):

Note: not every app shows real-time data from your own AIS transponder - check compatibility.

How reliable is AIS in bad weather or crowded areas?

AIS is generally highly reliable, even in bad weather. The data is transmitted digitally via VHF, which is not very sensitive to rain or wind. In busy areas (such as ports or popular waterways), however, not all messages may get through, especially for Class B transponders with 2-watt transmission power. Therefore, in busy sailing area 5 watts recommended.

What is the difference between terrestrial AIS and satellite AIS?

Terrestrial AIS is what you yourself receive on board via VHF antenna - real time, in your immediate vicinity (typically up to 20-30 miles).
Satellite AIS is captured by satellites, which collect signals from ships worldwide. You can see this data on sites like MarineTraffic or VesselFinder, but with some delay.

For on-board navigation terrestrial AIS most appropriate because of its immediate and up-to-date data.

What should I do if I sell my vessel - will my MMSI remain valid?

No. It MMSI number is linked to the vessel and to you as owner. If you sell your ship, then you must:

Have the registration of the MMSI number removed at Telecom Agency.
The new owner must apply for a new MMSI himself.

This prevents your data from still being broadcast by someone else.

If you take your VHF and/or AIS transponder with you to your new ship, then you must pass on the new name and data (dimensions) to the RDI and don't forget to update this in your VHF and AIS transponder too!

Do I always turn on my AIS even when I am lying still?

Yes, it is wise to keep your Leave AIS transponder always on, even when at anchor. This keeps you visible to other ships and prevents collision risks, especially in poor visibility or heavy traffic.

Can I temporarily turn off my AIS (e.g. for privacy reasons)?

Yes, you can use your AIS transponder switch off, but this is not recommended unless there is a valid reason for it (e.g. in high-risk areas where you don't want to be found). Please note that you invisible becomes for other ships and that this reduces your safety.

In some situations, such as participation in competitions, AIS may be temporarily switched off - but only in accordance with the regulations of that competition.