Study of Dumpy Level

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Dumpy level
Prepared by, Mr. Rahul S Chaudhari
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• Principle Axis of Dumpy Level
• Line of Collimation It is the line joining the
  intersection of the cross-hairs of the diaphragm
  to the optical centre of the object glass and its
  further continuation. This is also called as line
  of sight.
• Axis of Telescope It is the line joining,
  optical centre of eyepiece and object glass.
• Axis of Bubble Tube/Level Tube It is an
  imaginary line, which is tangential to the
  curvature of the bubble in the longitudinal
  bubble tube.
• Vertical Axis It is the axis about which the
  telescope can be rotated in a horizontal plane.

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BENCH MARKS
1.G.T.S.(Great Trigonometric Survey Bench
mark)- It is establish by Department of survey
of India with reference to M.S.L.( Mean sea
Level) considered as zero level at Karchi in
Pakistan. (MSL- It is the average height of the
sea for all stages of tides) 2.Permanent Bench
mark - those are set w.r.t. GTS by P.W.D. on
permanent objects like plinth, permanent
structures. 3.Arbitrary bench mark- those are
used for small survey work permanent bench
marks are not available nearby. 4. Temporary
bench mark- those are used for bog projects
normally continues for umber of days.
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• Height of Instrument Method/ Collimation Plane
  Method
• In this method, RL of HI is determined for each
  setup of the dumpy level and the RL of the other
  points are found out w.r.to the HI.
• Procedure
• i) Keep the leveling staff on BM take the
  reading called as BS.
• RL of HI RL of BM BS
• ii) Now, to find RL of intermediate points or
  change points, take the readings on those points
  called as IS or FS if it s the last reading for
  that setup.
• RL of Intermediate point RL of HI IS
• RL of change point RL of HI FS
• iii) To find new HI Shift the instrument at new
  position, take the reading on CP called as New
  BS,
• RL of new HI RL of CP New BS
• Iv) Then again find the RLs of all the other
  points w.r to new HI.
• V) Repeat the procedure till RLs of all the
  points is determined.
• Vi) After completion of leveling work,
  Arithmatical Check is found out by using the
  following formula
• (S of all BS) - (S of all FS) (Last RL
  First RL).

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H.I. Method / Collimation Plane Method
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• Rise And Fall Method
• Procedure
• i) The difference in staff readings between the
  consecutive point is found out.
• ii) If the difference is Positive it indicates
  Rise which is added in the RL of the previous
  points RL.
• iii) If the difference is Negative it indicates
  Fall which is subtracted from the RL of the
  previous points RL.
• iv) Repeat the same procedure till the RLs of all
  the points is determined.
• v) After completion of leveling work,
  Arithmatical Check is found out by using the
  following formula
• (S of all BS) - (S of all FS) (Last RL
  First RL) (S of Rise S of Fall).

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Rise Fall Method