Navigation Center Logo
Skip Navigation Consolidated Nav Info | DGPS Advisories | GPS Advisories / NANUs GPS Interference Notices | LNMs | Almanacs | Nav Rules| AIS | Contact Us | Search| Home
*** Special Notice: *** Please be advised that our mailing address has changed and is now: U.S. Coast Guard Navigation Center, NAVCEN MS 7310, 7323 Telegraph Road, Alexandria, VA 20598 - 7310. Mail sent to our previous address will not be delivered. Please contact us with concerns or questions. Our physical location remains the same. Thank you for your attention to this matter.
Navigation Rules
Primary Mission Areas:
Maritime Information:
RULE 21
DEFINITIONS

(a)     "Masthead light" means a white light placed over the fore and aft centerline of the vessel showing an unbroken light over an arc of the horizon of 225 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel, except that on a vessel of less than 12 meters in length the masthead light shall be placed as nearly as practicable to the fore and aft centerline of the vessel. [Inld]

(b)     "Sidelights" means a green light on the starboard side and a red light on the port side each showing an unbroken light over an arc of the horizon of 112.5 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on its respective side. In a vessel of less than 20 meters in length the sidelights may be combined in one lantern carried on the fore and aft centerline of the vessel, except that on a vessel of less than 12 meters in length the sidelights when combined in one lantern shall be placed as nearly as practicable to the fore and aft centerline of the vessel. [Inld]

(c)     "Sternlight" means a white light placed as nearly as practicable at the stern showing an unbroken light over an arc of the horizon of 135 degrees and so fixed as to show the light 67.5 degrees from right aft on each side of the vessel.

(d)     "Towing light" means a yellow light having the same characteristics as the "sternlight" defined in paragraph (c) of this Rule.

(e)     "All-round light" means a light showing an unbroken light over an arc of the horizon of 360 degrees.

(f)      "Flashing light" means a light flashing at regular intervals at a frequency of 120 flashes or more per minute.

(g)     "Special flashing light" means a yellow light flashing at regular intervals at a frequency of 50 to 70 flashes per minute, placed as far forward and as nearly as practicable on the fore and  aft centerline of the tow and showing an unbroken light over an arc of the horizon of not less than 180 degrees nor more than 225 degrees and so fixed as to show the light from right ahead to abeam and no more than 22.5 degrees abaft the beam on either side of the vessel. [Inld]

<-- Previous Rule --- Next Rule -->