The term aids to navigation, or navaids, includes lighted and unlighted beacons, buoys, and ranges. A beacon is a stationary visual navaid such as a lighthouse or a small single-pile structure. Lighted beacons are often called lights, and unlighted beacons are known as daybeacons. All beacons also have a daymark identification of one sort or another.
Range lights usually have both a high intensity lighting system and dayboards, but you will often encounter only the dayboards. Lining up these striped marks is similar to lining up the sights on a rifle.
There are five basic buoy shapes: can, cone, sphere, pillar, and spar. Topmarks can be cone, spherical, cylinder, or X-shaped. Red and green lights are used to match the colors on lighted lateral marks while yellow is reserved for special marks. White lights are used on safe water aids with an occulting, isophase, a single long flash or Morse code A flashing sequence. Cans are cylindrically shaped, are usually colored green, and have odd numbers. The conical shaped buoys, usually called Nuns, are red and have even numbers. The numbers are lowest at the seaward end of the channel and increase moving upstream toward land. Often, you see a buoy with both a number and a letter such as "9A." This usually happens when an additional buoy has been inserted in the channel and the USCG doesn't want to change the numbering sequence. Any buoy may use just a letter for identification. The number or letter appearing on a navaid will be identified in quotation marks on the chart. If the buoy is lighted, the color of the light will usually be the same color as the buoy and will usually be a flashing light.
Red and green horizontally banded buoys are used at junctions in a channel to show the preferred channel or to mark obstructions that may be passed on either side. If you want to stay in the preferred channel, consider the buoy to be all the same color as the top band and position your boat accordingly; for example, if the top band is red, keep the buoy to your starboard coming in toward land, and you will take the preferred channel.
Remember, there are two major types of buoyage systems: the lateral system and the cardinal system. The lateral system is partially explained above and is best suited for well-defined channels and the general direction of buoyage. The US navaid system is a lateral system. The cardinal system is best suited for coasts with numerous isolated rocks, shoals, islands, and for dangers in the open sea. The cardinal system is explained in Bowditch and should be reviewed before venturing into waters where it is used.
Chart No. 1 is a book containing a key to chart symbols. It contains a listing of all chart symbols used by the National Ocean Service (NOS), the Defense Mapping Agency (DMA), the International Hydrographic Organization, and on foreign charts reproduced by DMAHTC. Subjects covered include general features of charts, topography, hydrography, and aids to navigation. There is also a complete index of abbreviations and an explanation of the IALA buoyage system.
On large scale charts, the legend elements of lighthouses and other navigation lights are shown in this order: Characteristic, Color, Period, Height, Range, and Designation. For example, Fl (2) R 10s 80m 19M "6" is a lateral mark with the number 6 on it, has group flashing lights that present two red flashes every 10 seconds, has a height of 80 meters (261 feet), and is visible for 19 nautical miles under normal conditions.
Reliability Wise sailors donít rely entirely on floating navaids. These are often displaced or destroyed by storms or are removed for repair. They are also occasionally re-numbered or changed by the USCG, and if you haven't updated your charts with the Local Notices to Mariners, you can become disorientated. When you are depending on a particular navaid for your position, and it isn't there, or the numbering is different, don't panic. Immediately determine your position using radar, loran, GPS, or by bearings from other identifiable landmarks before you take any action that could place you in harmís way.
We will cover more of this aspect of navigation later on in the section on coastal navigation. See you here at SailNet.
|Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)|