AIS systems

AIS is short for Automatic Identification System, which is a globally developed protocol to increase safety. AIS sends and/or receives data through FM frequencies (same as the VHF). This is standardised information and is equal for all AIS (with special additions for class A AIS). It contains information about the ship: call sign, dimensions, course, speed, type, etc.

Although it is not intended to have 100% coverage, it offers important information about surrounding vessels.

AIS systems

PROs

Increased safety
More opportunities for sailing, even with low visibility
No more questions: “can we pass up front or should we adjust our heading?”
A large range (with an average of 10 nMile for yachts)
The range is unaffected by objects or obstacles
Better planning at bridges and floodgates
In contrast to radar the signal will always be picked up by others
Calling other ships is facilitated which has proven very popular among commercial vessels
The ability to track your friends

CONs

AIS is not standard on every ship. However all commercial vessels are obliged to use AIS
Visibility is not always desired, that is why we introduced the “silent mode” as a solution
Sometimes connecting all equipment can prove challenging, hence the need for a local specialist

BACK IN TIME

Back in 2001 the preparations for a new global system to promote safety and communication between ships were in full progress. Several studies and initiatives were integrated by the IMO (International Maritime Organization).

In mid-2002 the first AIS were installed on deep sea ships finally it becoming obligatory for those type of vessels in 2008. For inland shipping the regulations are less standardized, however in most areas there is an obligation for all vessels over 20 meters (ft 65) and all commercial vessels.

Watcheye was founded in 2010 to make this great feature available for leisure shipping as well. At the time most people were unfamiliar with AIS, although as we provided information and explained the possibilities, we became the specialist in AIS. This knowledge is our foundation to keep on developing.

AIS

What is AIS?

AIS is short for Automatic Identification System, which is a globally developed protocol to enlarge safety. AIS sends and/or receives data through FM frequencies (same as the VHF). This is standardised information and is equal for all AIS (with special additions for class A AIS). It contains information about the ship: call sign, dimensions, course, speed, type, etc. Although it’s not intended to have 100% coverage, it offers important information about surrounding vessels.

There are three categories in AIS:

Class A AIS:
This type of AIS is used for all commercial vessels.
Class B AIS:
This is AIS for leisure. The class B AIS has the same functionalities as the class A, but it has been simplified for yachts. For instance the data frequency has a larger interval.
AIS receivers:
AIS receivers receive information from surrounding vessels (both class A as class B), but don’t send information to others.

Which information does AIS transmit?

Statistic data, such as call sign, MMSI number, dimensions, type of ship (e.g. cargo, ferry, sailing)
Dynamic data (based on GPS), such as position, heading, speed, bearing, range, rate of turn
Travel data (only commercial vessels), such as destination, number of passengers, description of cargo

What is an MMSI number?

MMSI is short for Maritime Mobile Service Identity. This number will be officially allocated to your ship by the local authorities. The B transponder transmits this number, so you must apply for it before you can use your AIS.

Be aware that the MMSI number belongs to the ship, not to a person. So if the AIS is being reinstalled on another ship, another MMSI number must be programmed.

Because receivers don’t send information they don’t need an MMSI number.

What has VHF got to do with AIS?

The AIS uses VHF channels to transmit data. There are two channels available for AIS: when the first channel reaches its limit, the second channel will be enabled. A dual banded AIS transmits data through both channels, so you’re sure that there is no information missing.

When can I use AIS?

The AIS receiver can be used always and everywhere. Because it just receives information and it doesn’t send any data there are no restrictions.

The AIS transponder (class B AIS) is designed to use on ships. It is required to have an MMSI number programmed into the AIS. Because it sends data, it’s compulsory to have a VHF certificate and have the VHF radio switched on, so that others can contact you.

The pros and cons

Pro’s

Increases safety
There’s many information about surrounding ships available, which makes it easier to make clear and safe decisions
The range is about 10 nMile (or more, depending on the VHF antenna)
There’s no blockage of the signal by buildings, dikes, floodgates, like radar has
The available information provides possibilities to anticipate in many ways, such as controlling bridges and floodgates.

Con’s

Not every ship has AIS, so can’t see them all. Although commercial vessels are almost everywhere obliged to have AIS installed.
All data is public, perhaps there are moments you just don’t want to be seen. Watcheye offers the silent modus for these moments: you’ll still be able to see others, but they can’t see you.
Some people find it a bit complicated to install the AIS and connect it to their equipment. Please do not hesitate to contact us if you have questions about your installation.

Is Watcheye compatible with my other equipment?

AIS is an globally developed system. Which means that the data is standardised. It depends on the device to which the AIS is connected: is it AIS compatible? All manufacturers specifically mention if their product supports AIS.

There is a difference in which data protocol is used in the AIS. There are two universal protocols: NMEA0183 and NMEA2000. Watcheye is proud to mention that our products support both protocols.

What is a timeslot?

The background of the encryption of the data is based on TDMA, which is short for Time Division Multiple Access:

Class A: (commercial vessels), is based on SOTDMA (self organised TDMA) on 12W. It has a default transmit range of 2-3 seconds. If the status of the ship changes in moored or anchored, the interval increases.
Class B: (leisure vessels), is based on CSTDMA (carrier sense TDMA) on 2W. The default transmit range is every 30 seconds. If the speed is less than 2 knots the interval will increase up to 3 minutes.

These intervals are described for the dynamic information.

A static report is transmitted only every six minutes (for both class A and B).