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Protecting Markers
Chaining on Level Ground

Engineering Aid 3 - Beginning Structural engineering guide book
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simply driven near the hub or similar marker to serve as deterrence against machinery or heavy equipment traffic. On the other hand, permanent markers are protected by fixed barricades, such as  steel  or  concrete  casing. METHODS  OF  DIRECT  LINEAR MEASUREMENTS One   of   the   most   fundamental   surveying operations   is   the   measurement   of   horizontal distance between two points on the surface of the earth.  Generally,  there  are  two  basic  methods used: direct and indirect. Direct linear measure- ments,  as  explained  earlier  in  this  chapter,  are methods  used  for  determining  horizontal  distances with a tape (or chain) and/or with an electronic distance-measuring   instrument.   In   indirect methods,  the  transit  and  stadia  or  theodolite and  stadia  are  used.  This  section  will  discuss the   common   methods   used   in   direct   linear measurements. CHAINING  (OR  TAPING) The most common method used in determin- ing  or    laying   off   linear   measurements   for construction  surveys,  triangulation  base  lines, and  traverse  distances  is  often  referred  to  as CHAINING.  The  name  is  carried  over  from  the early  days  when  the  Gunter’s  chain  and  the engineer’s  chain  were  in  use.  Today,  it  is  more appropriate   to   call   this   operation   TAPING because  the  steel  tape  has  replaced  the  chain as  the  surveyor’s  measuring  device.  In  this manual, however, chaining and taping are used interchangeably. Identifying Duties of Chaining Party Members Obviously, the smallest chaining party could consist  of  only  two  people—one  at  each  end  of the tape. To lay off a line to a desired distance, one  person  holds  the  zero  end  of  the  tape  and advances  in  the  direction  of  the  distant  point, while the other holds a whole number of the tape at the starting point. The person ahead, holding the  zero  end,  is  called  the  HEAD  CHAINMAN; the other person is known as the REAR CHAIN- MAN. In ordinary chaining operations, if the distance being measured is greater than a tape length, it is  necessary  to  mark  the  terminal  point  with  a range  pole.  In  this  way,  the  rear  chainman  can keep  the  head  chainman  aligned  at  all  times whenever a full tape length or a portion of it is transferred  to  the  ground. The head chainman also acts as the recorder, and the rear chainman is responsible for keeping the tape in alignment. If more speed or precision in  taping  is  required,  additional  personnel  are assigned to the party. This relieves the chainmen of  some  of  their  duties  and  permits  them  to concentrate  primarily  on  the  measurement. For more precise chaining, a three-man party is  essential.  In  addition  to  the  head  and  rear chainmen, a stretcherman is added. The duties of the stretcherman are to apply and to maintain the correct  tension  on  the  tape  while  the  chainmen do the measuring. The head chainman still acts as  the  recorder  and  also  reads  and  records  the temperature  of  the  tape. Either of the two chaining parties described may   have   additional   personnel   assigned   as follows: .  A  recorder  keeps  a  complete  record  of  all measurements made by the taping party, makes any  sketches  necessary,  writes  descriptions  of stations  and  reference  points,  and  records  any other  data  required.  The  head  chainman  or  the chief  of  the  chaining  party  may  perform  these duties. . A rodman sets a range pole at the forward station to define the line to be taped, drives stakes to mark stations and reference points, carries the taping  stool  (discussed  later)  to  the  forward  point, and  performs  other  duties  as  directed. .  One  or  more  axmen  clear  lines  of  sight between  stations,  cut  and  drive  stakes,  and perform  other  duties  as  directed. . The chief of the chaining party directs the work   of   making   the   tape   measurements,   the establishment of stations, and other activities of the  party  in  the  field.  The  head  chainman performs these duties when there is no separate party  chief. Coiling and Throwing a Steel Tape Tapes  generally  come  equipped  with  a  reel; however, it is not always necessary to replace a steel  tape  on  the  reel  at  the  end  of  each  work period.  A  tape  can  be  easily  coiled  and  thrown into  a  circular  roll. 12-10







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