TACHEOMETRIC SURVEYS under the subject of SURVEYING made by Piyush andani

1. S.S. AGRAWAL
INSTITUTE OF
ENGINEERING AND
TECHNOLOGY
TACHEOMETRIC
SURVEY
CIVIL ENGINEERING DEPARTMENT
GIUDED BY:
Mr. Viraj N. Dhimmar
Assistant Professor
PREPARED BY:
En. No. Name
151230106005 DESAI PIYUSH.
151230106046 TRAPASIYA JENIISH.
151230106050 VIRADIYA PARTH.
161233106001 ANADANI PIYUSH H.
1

2. Subject:-Advanced Surveying
Topic:-Tacheometric Surveying

3. CONTENS
• DETERMINATION OF TACHEOMETRIC CONSTANTS
• MOVABLE HAIR METHOD OR SUBTENCE METHOD
• TANGENTIAL METHOD
• FIELD WORK IN TACHEOMETRY
• REDUCTION OF READING
• ERRORS IN TACHEOMETRY

4. STADIA CONSTANTS
• Stadia or tacheometric constants are:-
1. Multiplying constant
where,
• f =focal length of the lens
• i =stadia intercept
 The value of multiplying constant is generally 100.
i
f
A 

5. 2. Additive constant
B=(f+d)
where,
• f=focal length of the lens
• d= horizontal distance between instrument
 The value of additive constant. varies from 0.15 m
to 0.60 m.

6. • In tachometric surveying, instrument used is known as a
tachometer.
• With the help of a tachometer observations (stadia readings and
vertical angles) are taken and horizontal and vertical distances are
determined by using formulae.
• Before doing calculations we should known the values of two
constants for a tachometer to be used for survey work.
• Generally their values are mentioned in the catalogue supplied by
the manufacturer.
• Also the constants may be determined by:
1. Laboratory measurement
2. Field measurement

7. MOVABLE HAIR METHOD

8. MOVABLE HAIR METHOD
• In this method the staff intercept is kept constant, but the
distance between the stadia hairs is variable.
• This of theodolite is known type as substense theodolite.
• The diaphragm consists of a central wire fixed with the axis
of the telescope.
• The upper and lower stadia wires can be moved by
micrometer screws in a vertical plane.
• The distance by which the stadia wires are moved is
measured according to the number of turns of the
micrometer screws.

9. Fig. A special type diaphragm of a
moving hair theodolite

10. • The full turns are read on the graduated scale seen in the
filed of view and the fractional part of a turn is of the read
on the graduated drum micrometer screw placed one
above and one below the eye piece.
• The total distance through which stadia is the sum wires
move, equal to of the micrometer readings.
• If the distance between the instrument station and staff
position is within 200 m, an ordinary leveling staff may be
used and a full meter reading used for the purpose of
observing a constant intercept.
• For distances exceeding 200m it becomes difficult to read

11. • In such cases two vanes or targets fixed at a known
distance apart on a staff, are observed.
• A third target is fixed at the mid-point of the two targets.
• For taking the observation, the middle target is first
bisected by the central wire.
• Then the micrometer screws are simultaneously turned to
move the stadia wires until the upper and lower targets are
bisected.
• The readings are then noted.

12. Tangential Method

13. Tangential Method
• No stadia hairs
• Levelling staff with vanes or targets at known
distance
• Horizontal and vertical distances are
measured by measuring the angles of
elevation or depression.
• Some cases are discussed as follows:-

14. Case 1 : Both Angles of target are Angles of
elevation.

15. O’
O
S
h
V
B
A
D
C1
C2
θ2θ1
O’ -Instrument axis
O – Instrument station
C1 – Staff station
V – vertical distance between lower vane and axis of instrument
S – distance between the targets
θ1 - vertical angle by upper targets
θ2 - vertical angle lower targets
h – height of lower vane above the staff station

16. From figure we can say that,
Formula
21
2
21
21
2
1
tantan
tan
tantan
)tan(tan
tan
tan













S
V
S
D
DS
DV
DSV
RL of station C1 = RL of instrument axis + V - h

17. Case 2 : Both angles of target are Angles of
Depression

18. V
S
h
θ1 θ2
C2
A
B
C1
O’
O
D
O’ -Instrument axis
O – Instrument station
C1 – Staff station
V – vertical distance between lower vane and axis of instrument
S – distance between the targets
θ1 - vertical angle by upper targets
θ2 - vertical angle lower targets
h – height of lower vane above the staff station

19. From figure we can say that,
Formula
12
2
12
12
1
2
tantan
tan
tantan
)tan(tan
tan
tan













S
V
S
D
DS
DSV
DV
RL of station A = RL of instrument axis - V - h

20. Case 3 : One angle is angle of elevation and
the other is angle of depression.

21. O’ -Instrument axis
O – Instrument station
C1 – Staff station
V – vertical distance between lower vane and axis of instrument
S – distance between the targets
θ1 - vertical angle by upper targets
θ2 - vertical angle lower targets
h – height of lower vane above the staff station
S
V
h
θ1
θ2
C2
C1
O’
O
D

22. From figure we can say that,
Formula
21
2
21
1
2
tantan
tan
tantan
tan
tan











S
V
S
D
DVS
DV
RL of station A = RL of instrument axis - V - h

23. Thank you