periodical  announces  new  nautical  charts  and publications, new editions, cancellations, and changes to nautical charts and publications. It also summarizes events of the week as they affect shipping, advise mariners  of  special  warning  or  items  of  general maritime  interest,  and  includes  selected  accounts  of unusual  phenomena  observed  at  sea.  Distribution  of Notices to Mariners is made weekly to all U.S. Navy and  Coast  Guard  ships  and  to  most  ships  of  the merchant  marines. The classified chart and publication correction system is based on Classified Notices to Mariners, published on an as-needed basis by the DMAHTC to inform mariners of corrections to classified nautical charts and publications. HAND CORRECTIONS Corrections  on  charts  in  writing  should  be  kept clear of water areas as much as possible unless the objects referred to are on the water. When you are inserting  written  corrections,  be  careful  not  to obliterate any of the other information already on the chart. When cautionary, tidal, and other such notes are to be inserted, they should be written in a convenient but  conspicuous  place  where  they  will  not  interfere with any other details. The year and number of each Notices to Mariners from which corrections have been made are to be entered in ink at the lower left corner of the chart. Temporary changes should be made in pencil. For more information on chart corrections, visit your local Quartermaster. AIDS TO NAVIGATION LEARNING   OBJECTIVES:   Identify   and explain  the  aids  to  navigation,  including  lights, lighthouses,  buoys,  daybeacons,  ranges,  and fog  signals. In piloting, a ship's position is determined by bearings or ranges of objects whose exact location is shown on the area chart. Such objects are aids to navigation,  and  may  be  natural  or  man-made. Examples  of  natural  objects  are  prominent  hills, rocks, and mountains. Man-made objects include buildings,  TV  towers,  and  smokestacks  that  are coincidentally   located   where   they   can   be   of assistance to a navigator. Aids to navigation are lighthouses, lightships, minor lights, buoys, and daybeacons. Aids are placed so that, insofar as possible, they provide a continuous and  unbroken  chain  of  charted  marks  for  coast  and channel piloting. Most harbors and some coasts are well marked with man-made aids to navigation, yet no attempt has ever been made to mark every mile of the world's coastline. Such marking would be impractical because many regions are seldom navigated. In some areas, the lack of artificial aids makes it necessary to use  landmarks. LIGHTS A ship cannot suspend piloting operations when darkness falls and daytime navigational aids no longer can be seen. For this reason, aids to navigation are lighted whenever it is necessary. For purposes of identification,  lights  have  individual  characteristics regarding  color,  intensity,  and  system  of  operation. Some of a light’s characteristics may be printed near its  symbol  on  the  chart.  Detailed  information, including the height—which, combined with intensity and   observer's   height,   determines   the   light's visibility—is set forth in either List of Lights or Light Lists. The DMAHTC publishes seven volumes of List of  Lights.  The  volumes  are  divided  geographically, but exclude the United States and its possessions. This list contains a description of lighted aids to navigation (except harbor-lighted buoys) and fog signals.   Storm   signals,   signal   stations,   radio direction finders, and radio beacons located at or near lights are also mentioned in this list. Lights  located  in  the  United  States  and  its possessions are described in Light Lists, published by the U.S. Coast Guard. LIGHT CHARACTERISTICS White,  red,  green,  and  yellow  are  the  four standard colors for lights on aids to navigation. The significance  of  the  different  colors  is  important chiefly   with   regard   to   channel   buoys;   this significance is discussed later in the sections dealing with  buoys. Some navigational lights are fixed, meaning they burn steadily. The most important lights, however, go through repeated periods of systematic changes of light   and   darkness.   Those   characteristics   of   a navigational   light   are   the   most   valuable   for 9-7