Imagine being out in the middle of the ocean on a small sailing vessel in the middle of the night. It's dark and you are all alone with nothing to be seen except for stars and the moon. It is a very peaceful time and place. On the horizon a faint glow begins to appear. It's a curiosity. What would be making a glow out in the middle of the ocean? After watching the glow for perhaps 30 or more minutes, it turns into a set of bright lights on a huge ocean-going cargo vessel or tanker! Now your peace and quite turns into something altogether different. There is an immediate urgency to identify the pattern of lights which, if done correctly can tell you what you are seeing with your new neighbor. The light pattern can tell you if you are seeing the starboard or port side of the ship, whether is is coming towards you or away from you. It gets pretty tricky when the approach is at a weird angle or there are other working lights on the vessel. It gets even weirder when it is a tug pulling a big barge. It quickly gets more and more important to know if you are about to get run over. You keep a close watch and try to figure out what it is you are seeing. What can you do if you still can't tell? One choice is to use the radio and try to call them. So what do you say, "Hello big ship near me out here!" "Do you see me?" ? Probably not the most effective questions and not likely to get the answers you are looking for. Enter Automated Identification System (AIS). We have a AIS receiver on board Koinonia II and it is a fantastic system to have on board. Here's how it all fits together. AIS was initially mandated for use on all vessels over 300 tons by the International Maritime Organization. So all large ships are required to have AIS Class A tranceivers on board. Class B tranceivers are also available for recreational vessels. There are also simple receivers available. Each tranceiver and receiver is connected to a GPS unit so each AIS unit "knows where it is". The tranceivers broadcast on VHF frequencies certain information about themselves including a unique identifier known as the MMSI number, their position, course and speed. There is quite a bit of other information that is frequently sent as well (name of the vessel, size, destination, etc) Since mostly VHF frequencies are used the information is generally localized unless relayed somehow. Ships near one another form a loose network using the radio links. By listening to the data they receive and knowing their own position, course and speed, the system can determine how close you are to a collision with another vessel. The setup of the system allow you to configure the system to "Alert me when someone will come within 2 miles of me sometime in the future" or "Let me know if we will all be crushed to death within a couple of hours" This give you plenty of time to take evasive action. All of the ships within range of us show up on the GPS/Chartplotter at the helm. So at 25-30 miles out we can see all ship traffic and their vectors displayed right on the navigation screen. If it looks like a ship will come within a mile or so of us we will usually give them a call on the radio (we can get the ship name from AIS so it makes the call much more effective). We tend to offer to do anything they would like us to do to get out of their way (Charlie's idea) and it works great. That has happened twice so far on this trip and both times the ships have dramatically altered their course to give us a wide bearth. AIS make for a much safer and calm navigation experience and I am very grateful to have it on board.