Levelling.pptx for civil engineering and b tech

Syllabus
Levelling
• Definitions, technical terms, uses, details of
levels such as dumpy, tilting and auto levelling
staff, Temporary and permanent adjustments of
dumpy and auto level, corrections curvature,
refraction, combine and sensitiveness,
reciprocal levelling, collimation and rise & fall
method, errors, precautions.

Definition
• Levelling is defined as “an art of determining
the relative height of different points on,
above or below the surface”.

Principle of Levelling
• The principle of levelling is to obtain
horizontal line of sight with respect to which
vertical distances of the points above or
below this line of sight are found.

Object of levelling
The objective of Levelling
• To Find the elevation of given point with
respect to some assumed reference line called
datum.
• To establish point at required elevation
respect to datum.

Terms used in Levelling
Level surface
• It is the surface parallel to the mean spheroidal
surface of the earth
Level line
• Line lying on level surface.
Horizontal plane
• Horizontal plane through a point is a plane
tangential to level surface.
Horizontal line
• It is a straight line tangential to level line.

Terms used in levelling
Datum “It is an arbitrary level surface from which
elevation of points may be referred”. In India
mean sea level is considered as datum of zero
elevation it is situated at Karachi.
Mean Sea Level is the average height of sea for all
stages of tides it is derived by averaging the
hourly tide height over a period of 19 years.
Elevation or Reduced level It is height or depth of
any point above or below any datum. It is denoted
as R.L.

Bench Mark (B.M.) It is a fixed reference point of
known elevation with respect to datum.
Line of collimation It is a line joining the
intersection of cross hairs of diaphragm to the
optical centre of object glass and its continuation.
It is also known as line of sight.
Height of instrument It is the elevation of line of
collimation with respect to datum
Back sight It is a staff reading taken at a known
elevation. It is the first staff reading taken after
setup of instrument.

Fore sight( F.S.) It is the last staff reading taken
denoting the shifting of the instrument.
Intermediate sight.(I.S.) It is staff reading taken
on a point whose elevation is to be determined.
All staff reading between B.S. and F.S. are
Intermediate sight.
Change Point (T.P) It is a point on which both
fore and back sight are taken.

Instruments for levelling
are essentially
• The following instruments
required for levelling
• Level
• Levelling Staff

Instruments for levelling
• Level and types of level
• Level
• The instrument used to furnish horizontal line
of sight for observing staff readings and
determining R.L.s

Types of Level
• Dumpy level
• Tilting level
• Wye level
• Automatic level

Dumpy level
• The Dumpy level is a simple, compact and
stable instrument. The telescope is rigidly
fixed to its supports. Hence it cannot be rotated
about horizontal axis.

Tilting Level
• It is also known as I.O.P. level (Indian office
Pattern).In this level the telescope tilts about
its horizontal axis hence it is called tilting level

Wye level
• The essential difference between wye level and
other levels is that in wye level the telescope is
carried by two vertical wye supports. The
telescope can be rotated, moved or even raised
in wyes.

Automatic level
• It is also known as self aligning level. It is a
recent development. The fundamental
difference between auto level and other levels
is that the levelling is not manually but it is
levelled automatically. It is achieved by
inclination compensating device.

Levelling Staffs
• Levelling staffs are scales on which these
distances are measured.
• Levelling staffs are of two types
• Self Reading staff
• Target staff

Self Reading Staff
• The self reading staff can be read directly by
the level man looking through the telescope.
• Common types of self reading staffs
• Ordinary staff
• Sop-with telescopic staff
• Folding Staff

Ordinary Staff
• The one length staff, is solid and made
of seasoned wood, it is 3 m long and
graduated in the same way as the
telescopic staff

Folding Staff
• The folding staff is made up of well seasoned timber
such as Cyprus. It consists of two 2 m wooden pieces
with a joint assembly. Each piece of the staff is made
of one longitudinal strip without any joint. The folding
joint is of the detachable type with a locking device
at the back. The staff is joined together in such a way
that the staff may be folded from one another when
required.
• The staff has brass cap at the bottom. It has two
folding handles, with spring action. It is provided with
a circular bubble fitted at the back.

Sop-with Telescopic Staff
• Such a staff is arranged in three lengths
placed one into the other. It can be extended
to its full length by pulling. The top portion
is solid and the central box is hollow the total
length of staff is 4 m.
• The staff is graduated in such a way that
smallest division is of 5 mm. the value in m
are marked in red on the left and those in
decimetre are in black on the right.

Target Staff
• For very precise works and sight target staff
are used. A movable target is provided in this
staff.
• A vernier is provided on target to give precise
reading. In target staff level man directs the
staff man to move the target up and down
until it bisects by the line of sight. The staff
man observe the staff reading

Bench Marks
Bench mark is a point of known elevation
There are 4 kinds of bench marks
• GTS (Great trigonometrically survey bench
mark)
• Permanent bench mark
• Arbitrary bench mark
• Temporary bench mark

GTS Bench Mark
• They are the bench marks established with
very high degree of precision at regular
intervals by the survey of India Department all
over the country Their position and R.Ls
values above mean seal level which was
earlier located at Karachi and now it is taken
at Bombay High, Mumbai and is given in
catalogue formed by the department.

Permanent Bench Mark
• Permanent bench marks are fixed in between
GTS benchmarks by govt. agencies such as
railways, PWD, etc. This benchmarks are
written on permanent objects such as
milestones, culverts, bridges etc their value are
clearly written and their position are recorded
for future reference.

Bench Marks
Arbitrary Bench Marks
• These are reference points whose R.L.s are
arbitrarily assumed. They are used in small works
such bench mark may be assumed as 100 or 50 m
Temporary Bench Marks
• They are the reference points established during
the levelling operations when there is a break in
work, or at the end of day’s work the value of
reduced levels are marked on some permanent
objects such as stones, trees etc.

Temporary Adjustments of a
level
performed at every
• These adjustments are
setup of instrument
• Setting up of level
• Levelling of telescope
• Focusing of the eye peace
• Focusing of object glass

level
Setting up the level
This includes
• A) Fixing the instrument on tripod
• B) Levelling the instrument approximately by
Tripod

level
Levelling
Levelling is done with the help of foot screws. The
purpose of levelling is to make vertical axis truly
vertical. It is done with the help of foot screws
• A) Place the telescope parallel to a pair of foot screw
then hold the foot screws between thumb and first
finger and turn them either inward or outward until the
longitudinal bubble comes in the centre.
• B)Turn the telescope through 90 0 so that it lies parallel
to third foot screw, turn the screw until the bubble
comes in the centre.

level

level
Focusing the eye piece
• To focus the eye piece, hold a white paper in
front of object glass, and move the eye piece in
or out till the cross hair are distinctly seen.
Focusing of object glass
Direct the telescope to the levelling staff and on
looking through the telescope, turn the
focusing screw till the image appears clear and
sharp.

Permanent adjustment of level
• The establishment of a desired relationship
between the fundamental lines of a leveling
instrument is termed permanent adjustment. So,
permanent adjustment indicates the rectification
of instrumental error.
• The fundamental lines
• The line of collimation
• The axis of the bubble tube
• The vertical axis
• The axis of the telescope

• The following relationship between the lines are
desirable
• The line of collimation should be parallel to the
axis of the bubble
• The line of collimation should coincide with the
axis of the telescope
• The axis of the bubble should be perpendicular
to the vertical axis. That is, the bubble should
remain in the central position for all the
directions of the telescope.

• Two adjustment are required in the dumpy
level
• The first adjustment, to make the axis of the
bubble tube perpendicular to the vertical
axis
• The second adjustment, to make the line of
collimation parallel to the axis of the bubble
tube.

• Following procedure is adopted to make the line of
collimation parallel to the axis of the bubble tube.
• The level is set up on fairly level ground, with its legs
well apart, It is firmly fixed to the ground.
• The telescope is placed parallel to any pair of foot
screws and, by turning the foot screw either inward or
outward, the bubble is brought to the centre.
• The telescope is then turned through 90 0, so that it
lies over the third foot screw. Then by turning the third
foot screw the bubble is brought to the centre.
• The process is repeated several times until the bubble is
in the central position in both the direction.

0
• Now the telescope is turned through 180 and the
position of the bubble is noted.
• If the bubble still remains in the central position, the
desired relationship is perfect. If not, the amount of
deviation of the bubble is noted.
• Suppose the deviation is 2n division, Now by turning
capstan headed nut (which is at one end of the tube),
the bubble is brought half-way back (i.e. n division)
the remaining half-deviation is adjusted by foot
screws just below the telescope.
• The procedure of adjustment is continued till the bubble
remain in the central position of the telescope.

• The second adjustment is done by two peg method
• Two pegs A & B are driven at a distance apart on level
and firm ground. The level is set up at P, just mid-way
between A & B. After bringing the bubble to the centre
of its run, the staff readings on A & B are taken.
Suppose the reading are a & b
• Now the difference of level between A & B is
calculated , this difference is true difference, as the
level is set up just mid-way between BS and FS
• Then the rise or fall is determined by comparing the
staff reading.

• The level is shifted and set up at P1 (very near to A),
say at a distance d from A. Then after proper leveling,
staff reading at A & B are taken. Suppose the reading
are a1 and b1
• Then the apparent difference of level is calculated
• If the true difference and apparent difference are equal,
the line of collimation is in adjustment, if not the line of
collimation is inclined.
• Let e be the staff reading on B at the same level of the
staff reading a1
• Then e= a1 true difference

• Use positive sign in case of fall and negative sign when it is
rise
• If b1 is greater than e, the line of collimation is inclined
upwards and if b1 is less than e, it is inclined downwards.
• Collimation error= b1-e (in distance D)
• By applying the principle of similar triangle
• Correction to near peg
• C1= d (b1-e)
D
And correction to far peg
C2= D + d (b1-e)
D

Correct staff reading on A= a1 C1
Correct Staff reading on B= b1 C2
Then the cross-hair is brought to the calculated
correct reading by raising or lowering the
diaphagram by means of diphagram screw.

Classification of Levelling
• Simple Levelling
• Differential Levelling
• Fly Levelling
• Check Levelling
• Profile Levelling
• Cross Levelling
• Reciprocal Levelling
• Precise Levelling
• Trigonometric Levelling
• Barometric Levelling
• Hypersometric Levelling

Simple Levelling
• It is the simplest method used, when it is
required to find the difference in elevation
between 2 points.

Differential Levelling
• This method is used to find the difference in
the elevation between points if they are too far
apart or the difference in elevation between
them is too much.

Fly Levelling
• Fly levelling is just like differential levelling
carried out to check the accuracy of levelling
work. In fly levelling only B.S. and F.S. are
taken

Check levelling
• This kind of levelling is carried out to check the
accuracy of work. It is done at the end of the days
work in the form of fly levelling to connect the
finishing point and starting point.
Profile levelling or L-Section
• This method is used for taking levels along the
centre line of any alignment like road, railway
canal etc. The object is to determine the
the
undulations of the ground surface along
alignment

Profile levelling or L-Section

Cross-Sectioning
• This operation is carried out perpendicular to alignment
at an interval of 10, 20 ,30, 40 m. The idea is to make
an estimate of earthwork.
Precise Levelling
• It is used for establishing bench marks for future public
use. It is carried out with high degree of accuracy using
advanced instruments
Trigonometric Levelling
• In this method vertical distances between points are
computed by observing horizontal distances and
vertical angle between points.

Barometric Levelling
• In this method the altitude difference is
determined by means of a barometer.
• Barometric leveling is based on the fact that
the atmospheric pressure varies inversely with
height. In this method a barometer is used to
determine the differences in elevation of
points, which differ considerably in heights as
in a hilly area or mountainous country.

• It is chiefly used on exploratory or
reconnaissance surveys. Since the pressure of
the atmospheric at any point is constantly
changing and barometer reading are affected
by the temperature of the air
• Types of barometer in use are
• Mercury Barometer
• Aneroid Barometer

Hypsometric Levelling
The working of Hypsometry for determining the
elevation depends upon the fact that the
temperature at which water boils varies with
the atmospheric pressure. The boiling point of
water reduces at higher altitude thus knowing
the boiling point of water, the atmospheric
pressure can be calculated and knowing the
atmospheric pressure altitude or elevation can
be determined.

Hypsometric Levelling
• The altitudes of various points may be
determined by using hypsometer, also called as
thermo-barometer.

Reciprocal levelling
• Reciprocal Levelling:-
• This method is adopted to accurately determine the
difference of level between two points which are far
apart. It is also used when it is not possible to setup level
in midway between two points
• Let A and B be the two points on opposite banks of a river. It
is required to find out the level difference between A&B
• Setup the level very near to A and take the reading at A and B
let the reading be a1 and b1
• Shift the level and setup very near to B and observe A and B
to get reading a2 and b2
• Let d is the true difference of level between A and B, and
e=error due to curvature, refraction and imperfect
adjustment.

Reciprocal Levelling
• Thus to eliminate the error take an average of the
difference in elevation taken from 2 points
• i.e. from A the true difference will be
• =(b1-e)-a1
• Or d= (b 1- a1)-e
• From B the difference will be= b2-(a2-e)
• Or d= (b2-a2)+ e
• Adding these two eqn to eliminate e, we get
• Therefore d={(b1-a1)+ (b2-a2)}/2

Methods of Reducing Levels
Height of Instrument Method
• This method consist of finding H.I. for every
setup of instrument, and then obtaining the
R.L. of point of reference with respect to H.I

Rise and Fall Method
• This method consist of determining the
difference of level between consecutive points
by comparing each point with immediate
preceding point.

Errors in Levelling
The following are the different sources of Errors
• Personal Error
• The Instruments may not be levelled
• The focusing of eye piece and objective glass may not
be perfect
• The parallax may not be eliminated
• The position of staff may have changed
• Entry and recording in the field book may not be
correct
• The staff may not be fully extended, may not be held
vertical.

Errors in Levelling
Instrumental Error
• The Permanent adjustment of the instrument may
not be perfect. That is the line of collimation may
not be horizontal line.
• The internal arrangement of focusing tube may
not be correct
• The graduation of the staff may not be perfect
• Defective bubble tube, if the bubble tube is
sluggish, it may apparently be in the mid-position
even though the bubble line is not horizontal.

Errors in Levelling
Errors due to Natural Causes
• The Curvature of the Earth may affect the staff
readings when the distance of sight is long.
• The effect of refraction may cause a wrong
staff reading
• There are some errors in staff readings due to
high velocity wind

Common errors in Leveling
• Foresight and back sight not being taken on
exactly the same point
• Reading the staff upward instead of downward
• Reading of stadia hair
• Reading of wrong number of metre and decimeter
• Entering backsight in F.S and vice versa
• Transposing the figures
• Omitting an entry
• The leveling staff not being fully extended.

Curvature & Refraction Correction

Curvature Correction
• For long sights the curvature of earth can effect staff
readings. The line of sight is horizontal but the level line
is curved and parallel to the mean spheroidal surface of
the earth.
• The vertical distance between the line of sight and level
line at particular place is called the curvature correction
• The effect of curvature is to cause the object sighted to
appear lower than they really are.
• Curvature correction is always Subtractive(-)
• True staff reading=(Observed staff reading-
0.0785D2)m
• Where D= distance in Km.

Refraction
• The ray of light pass through layers of air of
different densities and refractor bent down. The
effect of refraction is to make the object appear
higher then they really are. Refraction varies
considerably with climate conditions.
However it is taken as,
• Cr=0.0112 D2m(+)
• Refraction is always additive
• True staff reading
• =Observed staff Reading+ Refraction
correction.

Example
• The following staff readings were observed
successively with a level the instrument is moved by
third, sixth and eighth readings.
• 2.228 :1.606 :0.988 :2.090 :2.864 :1.262 0.602 :1.982
:1.044 :2.684 m
• enter the reading in record book and calculate R.L. if
the first reading was taken at a B.M of 432.383m

H.I. Method
= LAST R.L-FIRST R.L= 431.432-432.384=-
CHECK Σ B.S-Σ F.S = 5.964-6.916= -0.952

CHECK ΣB.S-Σ F.S= 5.964-6.916= -0.952 = LAST R.L-FIRST R.L= 431.432-432.384=-0.952
ΣRISE-Σ FALL= 2.842-3.794=-0.952

• The following readings were taken with a dumpy
level and 4m leveling staff. The instrument was
shifted after 3rd and 6th readings. The readings are
2.665, 3.225, 2.905, 1.85, 0.98, 2.62, 1.585, 0.96,
0.425. m Enter the above readings in a page of level
book and calculate R.L. of points, if the first reading
was taken with a staff held on B.M. of 240 m. use
rise and fall method. Apply arithmetic checks

Station B.S. I.S. F.S Rise (+) Fall (-) RL Remarks
A 2.665 240 BM
B 3.225 0.56 239.44
C 1.85 2.905 0.32 239.76 3rd CP
D 0.98 0.87 240.63
E 1.585 2.62 1.64 238.99 6th CP
F 0.96 0.625 239.615
G 0.425 0.535 240.15
CHECK ∑ BS- ∑ FS ∑RISE- ∑ FALL L.RL –F. RL
6.1 5.95 2.35 2.2
∑ BS- ∑ FS= 0.15 ∑RISE- ∑ FALL
=0.15
L.RL –F. RL= 0.15

HI Method
Station B.S. I.S. F.S HI RL Remarks
A 2.665 242.665 240 .00 BM
B 3.225 239.44
C 1.85 2.905 241.61 239.76 3rd CP
D 0.98 240.63
E 1.585 2.62 240.575 238.99 6th CP
F 0.96 239.615
G 0.425 240.15
CHECK ∑ BS- ∑ FS L.RL –F. RL
6.1 5.95
∑ BS- ∑ FS= 0.15 L.RL –F. RL= 0.15

Example
• The Following observations were taken with dumpy level and
4 m leveling staff. The instrument were shifted after the 4th
and 7th reading. The first reading was taken on a bench mark
whose R.L. was 15.575 m. prepare a page of level book and
calculate RL of all the points. The observations were taken at
every 30 m interval. Also find out the gradient between first
and last point. Also draw the profile of ground. Use H.I.
Method. Observations are: 0.565, 1.250, 1.675, 3.695,0.125,
2.345, 0.500, 1.785, 2.535.

Observations are: 0.565, 1.250, 1.675,
3.695 (CP),0.125, 2.345, 0.500 (CP), 1.785, 2.535.
A 0.565 16.14 15.575 BM
B 1.250 14.89
C 1.675 14.46
D 0.125 3.695 12.565 12.44 CP
E 2.345 10.22
F 1.785 0.500 13.85 12.065 CP
G 2.535 11.315
2.47 6.73
∑ BS- ∑ FS= -4.26 L.RL –F. RL= -4.255

3.695 (CP),0.125, 2.345, 0.500 (CP), 1.785, 2.535.
Station B.S. I.S. F.S RISE FALL RL Remarks
A 0.565 15.575 BM
B 1.250 0.685 14.89
C 1.675 0.425 14.46
D 0.125 3.695 2.02 12.44 CP
E 2.345 2.22 10.22
F 1.785 0.500 1.845 12.065 CP
G 2.535 0.75 11.315
2.47 6.73
∑ BS- ∑ FS= -4.26 ∑RISE- ∑ FALL
=-4.26
L.RL –F. RL= -4.26

3.695 (CP),0.125, 2.345, 0.500 (CP), 1.785, 2.535.
A (0 m) 0.565 15.575 BM
B (30 m ) 1.250 0.685 14.89
C (60 m) 1.675 0.425 14.46
D (90 m) 0.125 3.695 2.02 12.44 CP
E (120 m) 2.345 2.22 10.22
F (150 m) 1.785 0.500 1.845 12.065 CP
G (180 m) 2.535 0.75 11.315
2.47 6.73
∑ BS- ∑ FS= -4.26 ∑RISE- ∑ FALL
=-4.26
L.RL –F. RL= -4.26

GRADIENT
• Gradient of line AG = Diff ofRLs
Length
• Gradient of lineAG = 4.260
180
= 1
42.25
= 1 in 42.25 Gradient.

Profile
15.575 14.89 14.46 12.44 10.22 12.065 13.315 R.L.
0 30 60 90 120 180 m Distance
Gradient : 1:42.25
m
Gradient : 1:42.25
m

Example
The following readings are taken on continuous
falling ground with staff of 4 m the are 0.4 m,
0.765, 1.270, 2.56, 3.22, 3.95, 0.390, 1.690, 3.5,
0.8, 1.920, 2.45, 3.98. Enter the reading in the
page of level book and calculate the RLs of all
point if the first reading was taken on Benchmark
of 100m.

0.400, 0.765, 1.270, 2.560, 3.220, 3.950, 0.390,1.690,3.500,0.800,1.920, 2.450,3.980
(Continuous Sloping Ground) 4m staff
A 0.400 100.4 100.00 BM
B 0.765 99.635
C 1.270 99.13
D 2.560 97.84
E 3.220 97.18
F 0.390 3.950 96.84 96.45 CP
G 1.690 95.15
H 0.800 3.500 94.14 93.34 CP
I 1.920 92.22 CP
J 2.450 91.69
K 3.98 90.16
∑ 1.59 11.43
CHECK ∑ BS- ∑ FS= -9.84 m L.RL –F. RL= -9.84 m

0.400, 0.765, 1.270, 2.560, 3.220, 3.950, 0.390,1.690,3.500,0.800,1.920, 2.450,3.980
(Continuous Sloping Ground) 4m staff
A 0.400 100.00 BM
B 0.765 0.365 99.635
C 1.270 0.505 99.13
D 2.560 1.29 97.84
E 3.220 0.66 97.18
F 0.390 3.950 0.73 96.45 CP
G 1.690 1.30 95.15
H 0.800 3.500 1.81 93.34 CP
I 1.920 1.12 92.22 CP
J 2.450 0.53 91.69
K 3.98 1.53 90.16
∑ 1.59 11.43 0 9.84
CHECK ∑ BS- ∑ FS= -9.84 m ∑RISE- ∑ FALL
=--9.84
L.RL –F. RL= -9.84
m

• The following is an incomplete page of level
book in which X indicates missing Entry line.
Calculate all the missing entries and complete
the page of level book .also give the usual
arithmetical checks.

MISSING READINGS
Station BS IS FS Rise Fall RL Remarks
A 2.560 100.0 BM
B 3.540 X X
C 3.200 X X
D 2.340 X X
E 1.950 X 1.08 X CP1
F 2.440 X X
G 3.465 X X

MISSING READINGS
A 2.560 100
B 3.54 X X
C 3.20 X X
D 2.34 X X
E 1.95 X 1.08 X CP
F 2.44 X X
G 3.46 X X
CHECK ∑ BS- ∑ FS L.RL –F.RL
∑ BS- ∑ FS= L.RL –F.RL=

A 2.560 100
B 3.54 0.98 99.02
C 3.20 0.34 99.36
D 2.34 0.86 100.22
E 1.95 1.26 1.08 101.3 CP
F 2.44 0.49 100.81
G 3.46 1.02 99.79
4.51 4.72
∑ BS- ∑ FS= -0.21 ∑RISE- ∑ FALL
=-0.21
L.RL –F. RL= -0.21
MISSING READINGS

Example
• The following consecutive readings were taken with a level
and a 4m staff at a common interval of 30m; The first reading
was taken at B.M. having R.L. =100m. The instrument were
shifted after the 4th and 9 th readings. Rule out a page of a
level book, enter the readings given and also calculate the
reduced levels of the points by the collimation method. Also
apply arithmetic checks.
• Consecutive readings are: 2.650, 1.745, 0.625, 0.260, 2.525,
2.160, 1.235, 0.870, 1.365, 0.625, 1.790, and 2.535.

Consecutive readings are: 2.650, 1.745, 0.625, 0.260 (CP), 2.525, 2.160,
1.235, 0.870, 1.365 (CP), 0.625, 1.790, and2.535.
A 2.65 100 m BM
B 1.745 0.905 100.905
C 0.625 1.12 102.025
D 2.525 0.260 0.365 102.39 CP
E 2.160 0.365 102.755
F 1.235 0.925 103.68
G 0.87 0.365 104.045
H 0.625 1.365 0.495 103.55 CP
I 1.79 1.165 102.385
J 2.535 0.745 101.64
K 5.8 4.16 4.045 2.405
∑
CHECK ∑ BS- ∑ FS= 1.64 m ∑RISE- ∑ FALL
= 1.64 m
L.RL –F. RL= 1.64
m

Consecutive readings are: 2.650, 1.745, 0.625, 0.260 (CP), 2.525, 2.160,
1.235, 0.870, 1.365 (CP), 0.625, 1.790, and2.535.
A 2.65 102.65 100 m BM
B 1.745 100.905
C 0.625 102.025
D 2.525 0.260 104.915 102.39 CP
E 2.160 102.755
F 1.235 103.68
G 0.87 104.045
H 0.625 1.365 104.175 103.55 CP
I 1.79 102.385
J 2.535 101.64
K 5.8 4.16
∑
CHECK ∑ BS- ∑ FS= 1.64 m L.RL –F. RL= 1.64 m

EXAMPLE
• The following consecutive readings were taken with a
level and a 4m leveling staff on a continuously
sloping ground at a common interval of 30 m on line
AB.
The reduced level (RL) of station A is 50.00. Calculate the
reduced levels at all the points where the leveling staff is placed.
Tabulate the results and apply usual checks. Also determine the
gradient of lineAB.
Chainag
e
0 30 60 90 120 150
Level 0.585 0.930 1.95 2.845 3.645 3.93
Station A B

EXAMPLE (Rise and Fall Method)
A (0 m) 0.585 50.00 BM
B (30 m ) 0.930 0.345 49.655
C (60 m) 1.950 1.02 48.635
D (90 m) 2.840 0.89 47.745
E (120 m) 3.645 0.805 46.94
F (150 m) 3.930 0.285 46.655
G (180 m)
0.585 3.930 0 3.345 3.345
∑ BS- ∑ FS= -3.345 m ∑RISE- ∑ FALL
= 3.345 m
L.RL –F. RL= 3.345
m

EXAMPLE (HI Method)
A (0 m) 0.585 50.585 50.00 BM
B (30 m ) 0.930 49.655
C (60 m) 1.950 48.635
D (90 m) 2.840 47.745
E (120 m) 3.645 46.94
F (150 m) 3.930 46.655
G (180 m)
0.585 3.930 3.345
∑ BS- ∑ FS= -3.345 m L.RL –F. RL= 3.345 m

References
• “Surveying and Levelling” Vol- I
Kanetkar and Kulkarni (2011)
• “ Surveying” Vol- I
Dr. B.C. Punamia

Levelling.pptx for civil engineering and b tech

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