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Booking
and Reduction - Collimation method
Levelling
observations are recorded either in specially ruled levelling books
or levelling sheets that are later stapled into a book. Information
that should be included on the sheet is the following:
- Heading
statement describing the job, date, personnel and Bench Mark data
used.
- The reduction
of the observations should be done by either the Collimation
method or the Rise
and fall method. The Rise and Fall method of booking
is discussed in the Series
levelling pages.
- Spaces
should be left for the relevant checks to be carried out.
- Column
left to enable to sets of observations to be compared or adjusted.
- The steps
for the reduction of the observations are as follows:
- Determining
the height of collimation and enter it into the appropriate column.
- Collimation
Height (CH) = RL BM+ BS
- Determine
the RL for each intermediate point by subtracting the intermediate
sight staff reading from the collimation height. Results are written
into the 'OUT' column.
- RL
Point = CH - InterSight
- The Foresight
reading is subtracted from the collimation height and compared
to the known RL of the Bench mark (BM).
- Reductions
must be checked by:
- CH
= (SBS + SIS + SFS + SRLout )/n
- N =
number of staff readings
- If a second
set of levelling observations are taken from a new point, the
staff observations are booked and reduced in a similar manner
to the first set.
- The reduced
RL for each point is placed in the REDUCEDBACK
column.
- The seconded
set of reduced RL's are transcribed onto the first levelling sheet
in the REDUCEDBACK column.
- If no gross
errors are evident the mean RL for
each point is determined and written into the adjusted column.
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The
Booking sheet method
- If Area
levelling is conducted as part of a Series levelling survey the
Rise and Fall booking method of is used. See
a field sheet example.
- If it all
the surveyed points are measured from a single setup then the
Collimation booking method is more commonly used, as it is simpler.See
a field sheet example.
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