Leveling
Faculty of Applied Engineering and
Urban Planning
Civil Engineering Department
2
nd
Semester 2008/2009
Surveying
1.
General Notes
2.
Common Mistakes
3.
Suggestions for Good Leveling
4.
Errors in Differential Leveling
Content
1.
Accuracy at field work comes first.
2.
If only difference between two points is needed, no
intermediate sights are required.
3.
BS and FS distances shall be equal
4.
Pay more attention to TP
5.
If the point to be measured for elevation is the
bottom of a bridge or a ceiling or the top of a barrier
such a wall or a column, staff is inverted so that
zero is at the point and negative sign is assigned to
the measured value.
General Notes
General Notes
Misreading the rod

reading 3.54 instead of 4.54
Moving the turning point

use a well
–
defined TP
Field note mistakes

work within your group to check
you records
Mistakes with extended rod
–
make sure the leveling
rod is fully extended
Common Mistakes
Level rod not vertical
Settling of leveling rod
Leveling rod not fully extended or incorrect length
Level instrument not level
Instrument out of adjustment
Environment

wind and heat
Common Mistakes
Level rod not vertical
Settling of leveling rod
Leveling rod not fully extended or incorrect length
Level instrument not level
Instrument out of adjustment
Environment

wind and heat
Common Mistakes
Anchor tripod legs firmly
Check the bubble level before and after each reading
Take as little time as possible between BS and FS
Try to keep the distance to the BS and the FS equal
Share the rod person with the level of the rod
Suggestions for Good
Leveling
Systematic Errors
Random Errors
Blunders
Errors in Differential
Leveling
Due to Earth’s Curvature and Atmospheric Refraction
Systematic Errors
BC = refraction of line of
sight from horizontal
BD = Error due to earth's
curvature
CD = Actual net error in the
staff reading = BJ

BG
Substituting R = 6365 km
BD = 0.0786 L
2
, Where BD is in m
L is in km
Refraction = BC≈BD/7 =0.0786 L
2
/7
Actual error in staff reading = CD = BD
–
BC , CD = 0.0786 L
2
/7
Therefore, to keep the effect of the earth's curvature
and atmospheric
refraction to a minimum
, it is advisable that the
distance between the level and the staff should not
exceed 100 m.
meters
in
CD
km
in
L
0.0673L
CD
2
m
100
L
mm,
1
CD
km
1
L
cm,
7
CD
Maladjustment of the level (collimation error)
Systematic Errors
)
(
tan
)
(
2
1
L
L
b
a
h
tan
tan
L
2
1
L
Correct elevation difference =m

n
)
(
)
(
)
(
)
(
2
1
2
1
b
a
b
a
h
EXAMPLE 4.2:
To check a level for the existence of collimation error, the level
was set up mid

way between points A and B and the following
two staff readings were taken:
1.92 m at A and 1.40 at B.
The level was then moved to
another position
and the
readings in Figure 4.14 were taken. Is there a
collimation
error? If the answer is yes, then calculate the angle of
inclination of the line of sight from the horizontal, as well as the
correct readings that should have been taken at A and B in the
second setup if there
was no collimation error.
SOLUTION:
There is a collimation error
From Equation (4.10),
0.52 = (1.75

1.20)

tan
α
(58

23) ,
α
=0
°
2'57"
Correct reading at A (m) =
1.75

58 tan
α
= 1.70 m
Correct reading at B (m) = 1.20

23 tan
α
= 1.18m
Check: difference in h =
1.70

1.18 = 0.52 m
2
1
55
.
0
2
.
1
75
.
1
h2
0.52m
1.40

.92
1
h
h
m
h
Questions?!
Reciprocal leveling
The elevation of point A in Figure is 917.34 m. From a setup on
the left bark, the BS reading at A was 1.44 m and the FS
reading at B was 1.90 m. At the second setup (on the right
bank) of the level, the BS reading at A was 1.80 m and the FS
reading at I3 was 2.34 m. Find the
elevation of point B.
SOLUTION:
Calculated RL for BM
2
= Known RL for BM
2
Where:
n
Level setups between two points
Δ
h
Elevation difference
Closure Error
ε
= h'
–
h
Where:
h'
Calculated Elevation
h
Known Elevation
Closure Error
Closure Error
i
i
i
j
i
Δh
for
correction
Closure
Δh
Measured
Δh
Corrected
ε
n
ni
Δh
correction
Closure
Closure Error
n
1
= 2,
Δ
h
1
= 1.74 m
n
2
= 1,
Δ
h
2
= 2.13 m
n
3
= 2,
Δ
h
3
=

3.10 m
n
4
= 4,
Δ
h
4
=

0.45 m
BM1 = 761.65 m
BM2 = 762.38 m
Closure Error
Δ
h
1
=
1.74 m
Δ
h
2
=
2.13 m
Δ
h
3
=

3.10 m
Δ
h
4
=

0.45 m
Σ
Δ
h =
0.32 m
BM2 = 762.38 m (known)
BM2 (Calculated)
= BM1 +
ΣΔ
h
= 761.65 m + 0.32 m
= 761.97 m
Closure Error
Closure Error
ε
= h'
–
h
= 761.97
–
762.38 =

0.41 m
BM2 = 762.38 m (known)
BM2 = 761.97 m (Calculated)
Closure Error
n
1
= 2,
Δ
h
1
= 1.74 m
n
2
= 1,
Δ
h
2
= 2.13 m
n
3
= 2,
Δ
h
3
=

3.10 m
n
4
= 4,
Δ
h
4
=

0.45 m
m
047
.
0
0.02
0.45

Δh
Corrected
02
.
0
(0.41)
9
4
Δh
m
24
.
3
0.14
3.10

Δh
Corrected
14
.
0
(0.41)
9
2
Δh
m
23
.
2
10
.
0
2.13
Δh
Corrected
10
.
0
(0.41)
9
1
Δh
m
82
.
1
08
.
0
1.74
Δh
Corrected
08
.
0
(0.41)
9
2
Δh
s
correction
Closure
2
4
1
3
1
2
1
1
ε
=

0.41 m
Group Work
Δ
h1 = 8.107 m
n1 = 4 setups
Δ
h2 =

17.212 m
n2 = 3 setups
Δ
h3 =

0.525 m
n3 = 4 setups
Δ
h4 =

2.387 m
n4 = 2 setups
Δ
h5 = 2.790 m
n5 = 4 setups
Δ
h6 = 9.206 m
n6 = 3 setups
Profile
Questions?!
Countouring
Faculty of Applied Engineering and
Urban Planning
Civil Engineering Department
2
nd
Semester 2008/2009
Surveying
Contouring
A contour
is an imaginary line connecting
points on the ground that have the same
elevation.
Contouring
A contour interval
the vertical distance or
elevation difference between two successive
contours
Depends on:
•
Scale
•
Purpose
•
Accuracy, time and cost
•
The topography
•
Area covered
Group Work
5
10
15
20
Group Work
20
15
10
5
Group Work
20
15
10
5
Group Work
5
10
15
20
Methods of Contouring
Griding
1
2
3
4
5
A
B
C
D
Methods of Contouring
Griding
12
14
13
10
11
12
11
cm
0.33
cm)
(1
10
13
10
11
x
x
1 cm
Methods of Contouring
Griding
h
2
h
1
h
o
(L)
h
h
h
h
x
1
2
1
o
x
L
Methods of Contouring
Griding
1
2
3
4
5
A
B
C
D
Discussion
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