CHAPTER  11 ELEMENTS OF SURVEYING AND SURVEYING  EQUIPMENT This chapter provides an overview of survey- ing in general with emphasis on the principles and procedures  of  basic  surveying  and  the  use  of various surveying equipments, instruments, and accessories.  As  an  EA,  you  should  realize  that accuracy in surveying is essential because other factors  affecting  sound  decisions  in  engineering practice are dependent upon the results of your survey. Surveying  is  a  science  that  deals  with  the determination of the relative positions of points on or near the earth’s surface. These points may be  needed  to  locate  or  lay  out  roads,  airfields,  and structures  of  all  kinds;  they  may  be  needed  for cultural,  hydrographic,  or  terrain  features  for mapping; and, in the military, these points may be  targets  for  artillery  and  mortar  fires.  The relative  horizontal  positions  of  these  points are  determined  from  distances  and  directions measured in the field, while their vertical positions are computed from the differences in elevations, which  are  measured  directly  or  indirectly  from  an established  point  of  reference  or  datum. The  earliest  applications  of  surveying  were  for the purpose of establishing the boundaries of land. Although  many  surveyors  are  still  preoccupied with  establishing  or  subdividing  boundaries  of landed properties, the purposes of surveys have branched  out  to  many  areas  that  parallel  the advancement  of  various  engineering  fields  and other  areas  of  civilization.  Surveyors  may  be called   upon   in   court   to   substantiate   definite locations  of  various  objects,  such  as  those involving   major   traffic   accidents,   maritime disasters, or even murder cases, in which direction and distance have a bearing. Surveying  continues  to  play  an  extremely important role in many branches of engineering. The results of today’s surveys are being used to map the earth above and below; for navigational charts  for  use  in  the  air,  on  land,  and  at  sea; and for other major survey operations for related tasks  in  geology,  forestry,  archeology,  and landscape architecture. As a surveyor in the Naval Construction  Force,  you  will  be  required  to submit  survey  results  before,  during,  and  after planning  and  construction  of  advanced  base structures, bridges,   roads, drainage   works, pipelines, and other types of conventional ground systems.  In  addition,  an  EA  assigned  to an  oceanographic  unit  may  be  involved  in hydrography  to  a  great  extent,  establishing  an offshore  triangulation  network,  depth  sounding, and  mapping. Again,  though  these  surveys  are  for  various purposes,  still  the  basic  operations  are  the  same— they involve measurements and computations or, basically,  fieldwork  and  office  work. CLASSIFICATION  OF  SURVEYING Generally,  surveying  is  divided  into  two  major categories:  plane  and  geodetic  surveying. PLANE  SURVEYING PLANE SURVEYING is a process of survey- ing  in  which  the  portion  of  the  earth  being surveyed is considered a plane. The term is used to designate survey work in which the distances or  areas  involved  are  small  enough  that  the curvature  of  the  earth  can  be  disregarded  without significant   error.   In  general,  the  term   plane surveying is applied to surveys of land areas and boundaries (land surveying) in which the areas are of limited extent. For small areas, precise results may be obtained with plane surveying methods, but  the  accuracy  and  precision  of  such  results  will decrease as the area surveyed increases in size. To make computations in plane surveying, you will use formulas of plane trigonometry, algebra, and analytical  geometry. A  great  number  of  surveys  are  of  the  plane surveying   type.   Surveys   for   the   location   and construction  of  highways  and  roads,  canals, landing fields, and railroads are classified under plane surveying. When it is realized that an arc 11-1