Adjustment in levelling for same point vs unknown point

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Homework Statement


in photo 391 , we can see that the levelling work is back to the same point , which is TBM1 . so , the adjustment of correction is (Bs -Fs ) / number of points ... But in 392-394 , the levelling work is from a known point to a different point ...
I'm wondering that is the adjustment correct ? It's given that adjustment = end closure / number of TP ...

Homework Equations

The Attempt at a Solution


In the table provided , we can see that there are only 2 TP , why the author divided by 3 for the case in 392-394 ? [/B]
 
Attachments
  • Two levelling field-book tables with columns BS, IS, FS, HOC or RISE, FALL, RL 1, CORR, RL 2 and REMARKS; the top table lists CP1, CP2, CP3, CP3', CP2', CP1' and TBM 1 = 24.968 with correction 0.001125 per station.
    391.PNG
    20.8 KB · Views: 498
  • Levelling field book table with columns BS, IS, FS, RISE, FALL, reduce level, adjustment, distance and remark, followed by end closure and allowable closure calculations.
    392.PNG
    27.7 KB · Views: 430
  • Levelling calculation: Adjustment = End closure/ΣTP, or Adjustment = Loop closure/ΣTP = 0.005/3 = 0.0017m per FS, above a reduced level table with BS, IS, FS, rise, fall, adjustment and distance columns.
    393.PNG
    12.1 KB · Views: 460
  • Levelling table with BS, IS, FS, RISE, FALL, REDUCE LEVEL, ADJUSTMENT and DIST columns, with purple and blue text above giving Adjustment = End closure/ΣTP, or Loop closure/ΣTP = 0.005/3 = 0.0017m per FS.
    393.PNG
    12.3 KB · Views: 485
  • Profile sketch of a levelling run from TBM1 to TBM2 with instrument set-ups, and a reduced level table listing BS, IS, FS, HOC, reduced levels, corrections and checks.
    394.PNG
    20.9 KB · Views: 441

Discussion

are 392-394 wrong ? because the correction are not applied to first 3 reading ...