3.  Administrative  drafting,  or  drafting  done in support of the administrative and operational functions  of  your  unit,  such  as  technical  and display  charts,  safety  and  embarkation  signs, project completions, and unit readiness graphics. In  performing  drafting  duties,  you  will  be working   from   sketches,   field   notes,   or   direct instructions Engineering Graphic from  your  drafting  supervisor. Charts and Graphs presentation   of   engineering   data means  using  CHARTS  and  GRAPHS,  rather  than numerical tables or word descriptions, to present statistical   engineering   information.   Properly constructed,  each  form  of  chart  or  graph  offers a sharp, clear, visual statement about a particular aspect  or  series  of  related  facts.  The  visual statement either emphasizes the numerical value of  the  facts  or  shows  the  way  these  facts  are related,   A   chart   or   graph   that   emphasizes numerical value is called quantitative; one that emphasizes  relationships  is  called  qualitative.  The trend  of  an  activity  over  a  period  of  time,  such as the mishaps summary report of a deployed unit rendered over a 6-mo deployment period, is more easily  remembered  from  the  shape  of  a  curve describing   the   trend   than   from   numerical statistics.  Successful  graphic  presentation  of engineering data requires as much drafting ability as   the   graphic   representation   of   engineering objects.   Lines   must   be   sharp,   opaque,   well contrasted,  and  of  uniform  weight.  Letters  and figures are normally executed with the standard lettering  set  according  to  accepted  conventions. Charts and graphs are classified as  technical or display charts. TECHNICAL   ENGINEERING   CHARTS usually are based on a series of measurements of laboratory  experiments  or  work  activities.  Such measurements  examine  the  quantitative  relation- ship between a set of two factors or variables. Of the two variables, one has either a controlled or regular  variation  and  is  called  the  independent variable.  The  other  is  called  the  dependent variable because its values are related to those of the  independent  variable.  The  line  connecting plotted points is called a curve, although it may be   broken,   straight,    or   curved.   The   curve demonstrates   the   relationship   between   the variables  and  permits  reading  approximate  values between  plotted  points. DISPLAY  CHARTS  are  organized  primarily to  convey  data  to  nontechnical  audiences.  The message  presents  a  general  picture  of  a  situation, usually comparative. There are many varieties of display charts, including bar charts, status charts, and training aids. In a SEABEE battalion, display charts  are  frequently  used  in  operations  and training departments. When so used, they must conform to minimum standards prescribed by the command. Any  construction  job  involves  quantities  of people,   materials,   and   equipment.   Efficient operation  and  completion  of  the  job  result  from planning, organization, and supervision. Graphic presentation  of  data  is  important.  Statistics  based on the results of past jobs with similar working conditions   provide   a   basis   for   predicting   the amount  of  time  that  a  proposed  job  will  take. These  statistics  offer  the  best  possibilities  for study when presented graphically, usually in the form  of  a  curve.  The  prediction  of  expected achievement usually is presented as a bar chart and  is  called  a  time-and-work  schedule,  When  the scheduled  work  progress  is  compared  with  the actual   progress   (work   in   place),   the   chart   is called  a  progress  chart. Drafting Guidelines As  stated  earlier,  there  are  definite  guidelines in  drafting.  These  guidelines  provide  uniform interpretation  of  all  engineering  drawings.  Any drawing  prepared  by  or  for  the  Navy  must  be prepared  following  the  latest  military  standard (MIL-STD),   Department   of   Defense   Standard (DOD-STD),  and  applicable  NAVFACENGCOM design   manuals.   For   subjects   not   covered   by these   references,   you   might   refer   to   civilian publications, such as the  Architectural   Graphic Standards.  Or, you may devise your own symbols, provided that any nonstandard features in your drawing  are  supported  with  adequate  explanation by  notes  or  by  legend. Many  drawings  continue  in  use  for  years. Therefore,  you  will  have  occasion  to  work  with drawings that contain obsolete symbols. Look for a legend on the drawings; it should help you in reading symbols with which you are not familiar. If there is no legend, study the drawing carefully and you should be able to interpret the meaning of  unfamiliar  symbols  and  abbreviations. DoD  drawing  standards,  which  are  constantly being  updated,  are  published  by  the  Assistant Secretary   of   Defense   (Supply   and   Logistics), Office of Standardization. Any Navy activity can 2-2