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Figure 14-20.-Sample field notes from cross-section leveling at first three stations shown in figure 14-7.
PRECISION IN LEVELING; MISTAKES AND ERRORS IN  LEVELING

Engineering Aid 3 - Beginning Structural engineering guide book
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and right in the notebook must correspond to left and  right  in  the  field. Figure   14-20   shows   field   notes   for   cross- section  levels  taken  on  the  first  three  stations shown  in  figures  14-16  and  14-17.  On  the  data side, only the station and the HI need to be listed. On the remarks side, each entry consists of a point elevation, written over the distance of the point from  the  center  line.  The  computed  elevation, determined by subtracting the rod reading from the HI, is written in above as shown. Note that the  rod  reading  at  the  center  line  is  the  5.5-ft vertical  distance  from  your  line  of  sight  to  the ground. Also, notice that the center-line elevation written in at each station. is the one obtained in the profile level run. You obtain the HI for each station   by   simply   adding   together   these   two figures. Double  Rodding Double  rodding  is  a  form  of  differential leveling in which a continuous check is maintained on  the  accuracy  of  the  leveling  procedure.  It  is called  double  rodding  because  it  can  be  done  most conveniently  by  two  rodmen.  However,  it  is possible  to  carry  out  the  procedure  using  only  one rodman. In  double  rodding,  you  determine  the  HI  at each  setup  point  by  backlights  taken  on  two different  TPs.  If  no  mistake  or  large  error  has been made, the result will be two HIs that differ slightly  from  each  other.  Elevations  computed  this way  will  also  differ  slightly.  In  each  case,  the average is taken as the elevation. Figure 14-21 shows double-rodded level notes for a run from one BM to another by way of three Figure  14-21.-Sample  field  notes  from  double-rodded  levels. 14-20







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