As a sailing and motor cruising instructor who learnt to sail long before GPS was available I am confident in using traditional navigational techniques and am not over reliant on modern technology. I am however very enthusiastic about this new bit of equipment.
It is a new and inexpensive system whereby we sailors and motor cruisers can find the name of a ship, its position, course and speed long before a collision is likely. Most ships now have AIS transponders and receivers, both of which will be linked to the ships radar and GPS. The system works as a result of a VHF signal being transmitted from a ships AIS transponder.Commercial vessels over 300 tons and all passenger vessels are required to have installed an AIS system. This equipment transmits the ships name, MMSI number, position, speed, course, heading and even its destination every few seconds. It enables other vessels and port authorities to get a better picture of what's happening around them - a bit like air traffic control.
All we really need in a yacht or a motor cruiser is a receiver, so that we can see what ships are doing and where they are and where they are going! Nasa Marine's is so far the first company to produce an inexpensive AIS receiver designed specifically for use in smaller vessels, it costs around 385 euros. This new stand alone instrument shows AIS details on a mono screen. The display looks like a simple ARPA (Automatic Radar Plotting Aid) radar screen, showing targets ranges and bearings relative to your boat, with a vector line showing their course etc. Each Targets AIS details will also be available in a tabular form shown to the right of the screen itself.The display, with ranges of 1,2,4,8,16 and 32 nautical miles shows AIS carrying vessels in a format normally associated with conventional radar. A trail of previous positions clearly shows the relative track of all the targets on the screen. A box to the right of the screen displays the speed over the ground, the vessel name,MMSI number and the latitude and longitude of any target selected by the user.
The unit consists of a dual frequency AIS receiver, demodulator, signal processor, and a backlit matrix display. It receives an NMEA input (RMC) from the boats GPS which puts your boat at the centre of a “radar-like” display. All other AIS carrying vessels are displayed with bearing and range relative to your boat.
Any vessel on the screen can be highlighted and its data will be displayed on the right of the screen. The data includes the ships name, MMSI number, position, speed, course and heading, distance off, plus latitude and longitude. Each vessel leaves a trail of previous positions so you immediately get a feeling for what’s going on.
In the event that any vessel looks to be at risk of collision with you it can be selected and its data displayed. The MMSI number is immediately available so that in the last resort a DSC call can be made directly to the vessel.
The photographs above and below were taken recently by a friend Peter Hart, he was motor-sailing in his Yacht ‘Wishstream’ a Nicholson 46 in close proximity to a ship called Vasiliy Shuksin. On his AIS screen two vessels can be seen, Peter has highlighted the left hand one and the information on the right hand side of the screen is everything that Peter needed to know about that ship. Firstly the screen is set to show north as being to the top of the screen, then ‘scale 4 nm’ is the distance from the cross in the centre of the screen which is ‘Wishstream’ to the outer ring. Then 273314100 is the ships MMSI number (VHF/DSC calling number) followed by the ships name. Then ‘Range 1.0’ shows that the ship is just one mile away. Then the ships latitude and longitude followed by its heading, course over the ground and its speed over the ground, which is 9.3 knots.
The RYA (Royal Yachting Association) would like to draw to the attention of anyone who uses VHF or AIS equipment on board a vessel to Marine Guidance Note MGN 324 (M+F) issued by the Maritime and Coastguard Agency (MCA).
This notice draws attention to the correct operation of VHF and AIS equipment, in line with both the International Telecommunications Union (ITU) Radio Regulations and the Collision Regulations.
Collisions, where VHF communications have been used to agree a deviation from the collision regulations, have been highlighted, and making such arrangements is discouraged.
For people operating craft which come under the umbrella of the RYA, the messages within this notice are simple:• There must be a VHF licence holder onboard the vessel
• The appropriate channel should be used at all times
• Check the channel is clear before transmitting
• Ensure that the sending and receiving stations are identified in each transmission
• Non-essential transmissions are to be avoided
Do not agree to deviate from the collision regulations in a potential collision situation. You may not be communicating with the vessel you think, language barriers may cause misunderstandings and a collision could be created rather than avoided.
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