It used to be that on a foggy night going into a harbor frequented by large ships, your biggest hope was to be a small blip that got noticed on a ship's radar screen.  A new system called AIS, or Automatic Information Systems, makes it much easier to get noticed by ships.  This system also allows you to 'see' other large ship traffic in the area.  The system uses a GPS receiver that transmits your position and receives vessel traffic information over a VHF frequency.  When set up, it then overlays position, color coded vessel type such as cargo, passenger, yacht, tug, or fishing vessel along with speed, and course right onto your chartplotter!  For many vessels you can see a picture by placing your cursor on the vessel in question on your chartplotter.  Using a VHF radio frequency, it has better range if the antenna is mounted on the highest part of your boat.  You can add an AIS receiver to many of the newer chart plotters such as Furuno, Raymarine, and others.  To see how the system works, you can also watch traffic on the web at www.marinetraffic.com or with the latest iphone application.  With a properly installed working AIS set up on your boat, other AIS equipped vessels will know more about your position than on a traditional radar scope.  Don't expect it to tell you whether anyone is paying attention at the helm of other vessels or to pick up floating debris, small vessels without AIS receivers, lobster pots, or many other unmarked hazards. At sea there is no substitute for common sense, a working radar, and experience, but AIS is a great tool to have especially at night or in the fog.  To find out more about AIS visit any local marine electronics store.