Signalman 1 & C - Historic Naval Ships Association

Greenwich hour angle of the mean sun, expressedin time units plus 12 hours.GUIDE—Vessel designated in a formation or dispositionas the one for others to keep station on.GUN SALUTE—Blank shots fired to honor adignitary or in celebration.H-HOUR—The term used to designate the time foran operation to commence.HEAD-ON VESSEL—One vessel meeting anotheron a reciprocal or nearly reciprocal courseinvolving risk of collision.HOIST—To move an article vertically upward bymeans of some hoisting rig.HULL DOWN—Said of a vessel when, because ofdistance and curvature of Earth, only thesuperstructure is visible.INFRARED—Transmission of signals by lightoutside the visual spectrum. This method, whichmay be directional or nondirectional, necessitatesthe use of special equipment and affords greatersecurity than normal visual means.IRISH PENNANT—A loose end of line carelesslyleft dangling.JANAP—Joint Army-Navy-Air Force Publication.LATITUDE—Distance north (N) or south (S) of theequator, expressed in degrees and minutes.LONGITUDE—Distance east (E) and west (W) of theprime meridian, which runs through Greenwich,England.LORAN—An electrical navigation system by whichhyperbolic lines of position are determined bymeasuring the differences in the time of receptionof synchronized pulse signals from two fixedtransmitters.MANEUVERING BOARD—A polar coordinatedplotting sheet devised to aid in the solution ofproblems involving relative movement.MASTHEAD LIGHT—The white running lightplaced over a vessel's fore-and-aft centerlineshowing an unbroken light over an arc of thehorizon of 225°, fixed to show the light from rightahead to 22.5° abaft the beam on either side of thevessel.MEAN TIME—Time based upon the rotation ofEarth relative to the mean sun.MERCATOR PROJECTION —A conformalcylindrical map projection in which the surface ofa sphere or spheroid, such as Earth, is conceivedon a cylinder tangent along the equator.MESSENGER—(l) A line used to haul anotherheavier line across an intervening space; (2) Onewho delivers messages.NEED-TO-KNOW —A criterion used in securityprocedures that requires the custodians ofclassified information to establish, prior todisclosure, that the intended recipient must haveaccess to the information to perform his/herofficial duties.NIGHT VISION DEVICES—Precision instrumentsthat use electronic optics for observation,surveillance, and navigation. Also referred to asNight-Vision Sights.NTP—Naval Tactical Publication.NWP—Naval Warfare Publication.OCCULTING LIGHTS—A navigational aid inwhich the period of light is equal to or more thanthe period of darkness.OCCUPATIONAL STANDARDS—The minimumrequirements for enlisted occupational skills of acertain rate or rating.OFFICIAL INFORMATION—Information that isowned by, produced by, or subject to the controlof the United States Government.OFFICIAL VISIT—A formal visit of courtesyrequiring special honors and ceremonies.OMEGA—An electronic navigational system.PELORUS—Device for taking relative bearings.PERSONNEL QUALIFICATION STANDARDS—Qualification for officers and enlisted personnelto perform certain duties.PHYSICAL SECURITY—That part of securityconcerned with physical measures designed tosafeguard personnel; to prevent unauthorizedaccess to equipment, installations, material anddocuments; and to safeguard them againstespionage, sabotage, damage, and theft.POSITION ANGLE—The number of degrees anobject seen in the sky is above the horizon.POWER-DRIVEN VESSEL—Any vessel propelledby machinery.AI-2