ONBOARD  PLANS—See SHIP’S PLANS. ORTHOGRAPHIC  PROJECTION—A view produced when projectors are perpendicular to the plane of the object. It gives the effect of looking straight at one side. PARTIAL  SECTION—A sectional view consisting of less than a half section. Used to show the internal structure of a small portion of an object. Also known  as  a  broken  section. PERPENDICULAR  —Vertical lines extending through  the  outlines  of  the  hull  ends  and  the designer’s   waterline. PERSPECTIVE —The   visual   impression   that,   as parallel lines project to a greater distance, the lines move  closer  together. PHANTOM  VIEW—A view showing the alternate position of a movable object, using a broken line convention. PHASE—An  impulse  of  alternating  current.  The number  of  phases  depends  on  the  generator windings.   Most   large   generators   produce   a three-phase current that must be carried on at least three  wires. PICTORIAL DRAWING—A drawing that gives the real appearance of the object, showing general location, function, and appearance of parts and assemblies. PICTORIAL WIRING DIAGRAM —A    diagram showing  actual  pictorial  sketches  of  the  various parts of a piece of equipment and the electrical connections  between  the  parts. PIER —A vertical support for a building or structure, usually  designed  to  hold  substantial  loads. PITCH —The distance from a point on a screw thread to  a  corresponding  point  on  the  next  thread, measured  parallel  to  the  axis. PLAN  VIEW —A view of an object or area as it would appear from directly above. PLAT—A map or plan view of a lot showing principal features,  boundaries,  and  location  of  structures. POLARITY  —The direction of magnetism or direction of flow of current. PROJECTION —A technique for showing one or more sides of an object to give the impression of a drawing of a solid object. PROJECTOR  —The theoretical extended line of sight used to create a perspective or view of an object. RAFTER—A  sloping  or  horizontal  beam  used  to support a roof. RADIUS—A straight line from the center of a circle or sphere to its circumference or surface. REFERENCE  DESIGNATION—A combination of letters and numbers to identify parts on electrical and electronic drawings. The letters designate the type of part, and the numbers designate the specific part.  Example:  reference  designator  R-12  indicates the 12th resistor in a circuit. REFERENCE   NUMBERS—Numbers   used   on   a drawing to refer the reader to another drawing for more  detail  or  other  information. REFERENCE PLANE—The  normal  plane  that  all information is referenced REMOVED SECTION—A drawing of an object’s internal cross section located near the basic drawing of the object. REVISION  BLOCK—This block is located in the upper right corner of a print. It provides a space to record  any  changes  made  to  the  original  print. REVOLVED SECTION—A drawing of an object’s internal cross section superimposed on the basic drawing  of  the  object. ROOT—The surface of the thread corresponding to the minor  diameter  of  an  external  thread  and  the  major diameter of an internal thread ROTATION —A view in which the object is apparently rotated or turned to reveal a different plane or aspect, all shown within the view. ROUND—The rounded outside corner of a metal object. SCALE—The relation between the measurement used on a drawing and the measurement of the object it represents. A measuring device, such as a ruler, having  special  graduations. SCHEMATIC   DIAGRAM—A diagram using graphic symbols to show how a circuit functions electrically. SECTION —A view showing internal features as if the viewed object has been cut or sectioned SECTION LINES—Thin,  diagonal  lines  used  to indicate the surface of an imaginary cut in an object. AI-4