This document provides information about tacheometric surveying. It discusses various tacheometric constants including multiplying and additive constants. It describes three methods for determining distances using a tacheometer: movable hair method, tangential method, and examples of using angles of elevation and depression to calculate distances. The document also lists common topics covered in tacheometric surveying such as determining constants, field work, and reducing observations.

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