Principle of Leveling:
1. Simple leveling:
It
is the simplest operation in leveling when it is required to find the
difference in elevation between two points both of which are visible from a
single position of the level. Suppose A and b are two such point and level is
set up at 0, approximately mid way between. A and B but not necessary on the
line joining them, after finding the reading on point A and point B, let the
respective reading on A and B be 2.340 and 3.315 difference between them is
3.315-2.340=0.795 m.
is the simplest operation in leveling when it is required to find the
difference in elevation between two points both of which are visible from a
single position of the level. Suppose A and b are two such point and level is
set up at 0, approximately mid way between. A and B but not necessary on the
line joining them, after finding the reading on point A and point B, let the
respective reading on A and B be 2.340 and 3.315 difference between them is
3.315-2.340=0.795 m.
2. Differential leveling:
This
method is used in order to find out the difference in elevation between two
points.
method is used in order to find out the difference in elevation between two
points.
- If they too apart.
- If the difference in elevation
between them is too great.
In
such cases it is necessary to set up the level in several positions and to work
in a series of stages. The method of simple leveling is employed each of the
successive stages. The process is also known as compound continues leveling. Methods of
Determination of the Reduced Level of Point from the Staff Reading
such cases it is necessary to set up the level in several positions and to work
in a series of stages. The method of simple leveling is employed each of the
successive stages. The process is also known as compound continues leveling. Methods of
Determination of the Reduced Level of Point from the Staff Reading
1. Collimation Method:
It
consist of finding the elevation of the plane of collimation ( H.I.) for
every set up of the instrument, and then obtaining the reduced level of point
with reference to the respective plane of collimation.
consist of finding the elevation of the plane of collimation ( H.I.) for
every set up of the instrument, and then obtaining the reduced level of point
with reference to the respective plane of collimation.
- Elevation of plane of
collimation for the first set of the level determined by adding back side
to R.L. of B.M. - The R.L. of intermediate point
and first change point are then obtained by starching the staff reading
taken on respective point (IS & FS) from the elation of the plane
collimation. [H.I.] - When the instrument is shifted
to the second position a new plane collimation is set up. The elevation of
this plane is obtained by adding B.S. taken on the C.P. From the second
position of the level to the R.L. C.P. The R.L. of successive point
and second C.P. are found by subtract these staff reading from the
elevation of second plane of collimation Arithmetical check
Sum of B.S. – sum of F.S. = last R.L. – First R.L.
2. Rise and Fall Method:
It
consists of determining the difference of elevation between consecutive points
by comparing each point after the first that immediately preceding it. The
difference between there staff reading indicates a rise fall according to the staff
reading at the point. The R.L is then found adding the rise to, or subtracting
the fall from the reduced level of preceding point.
consists of determining the difference of elevation between consecutive points
by comparing each point after the first that immediately preceding it. The
difference between there staff reading indicates a rise fall according to the staff
reading at the point. The R.L is then found adding the rise to, or subtracting
the fall from the reduced level of preceding point.
Arithmetic
check
check
Sum
of B.S. – sum of F. S. = sum of rise – sum of fall = last R. L. – first R.L. Booking the staff readings:
of B.S. – sum of F. S. = sum of rise – sum of fall = last R. L. – first R.L. Booking the staff readings:
The
following points may be kept in mind entering the readings in a level field
book.
following points may be kept in mind entering the readings in a level field
book.
- The reading should be entering
in the respective columns and in order their observation. - The first page is always a back
side and the last one is ways a foresight. - It a page finished with
an IS reading, the reading is entered in the IS and FS columns on that
page and brought forward to the next page. - The FS and BS of any change
point are entered in the same horizontal line. - The RL of the line of the
collimation is entered in the same horizontal line. - Bench marks and change points
should be clearly described in the remark column.
Specimen pages of level field book: Collimation system
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Station
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Distance (cm)
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Reading
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RL of plane of
collimation [HI] |
Reduced level
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Remarks
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BS
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IS
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FS
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A
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B.M.
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B
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C
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Arithmetic check
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Sum of BS-Sum of FS= Last RL-1st -RI
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Specimen pages of level field book: Rise & Fall System
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Station
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Distance(m)
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Reading
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Rise
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Fall
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Reduce level
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Remarks
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BS
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IS
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FS
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B.M
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A
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B
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C
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Check :
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BS-FS=Rise-fall=last RL -1st-Rl
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