Theodolite seting up.pdf

Theodolite seiting up

1. Engineering Technical College
highwayEngineering Dept.
Engineering Survey-2
BASICSOFTHEODOLITE
ANDANGLEMEASUREMENTS
Prepared by
Lecturer: Razhan Sherwan
1

2. WHATISANGLE
An angle is defined as the amount of turn
between two straight lines that share a common
end point. Angles are measured in degrees.
The symbol used for degrees is a little circle °
2

3. TERMSASSOCIATEDWITHANGLES
VERTEX -The vertex of an angle is the common point
where the two lines meet.
ARM -The arms of an angle or sides are the lines that
make up the angle.
DEGREES -The size of the angle is measured in degrees
and usually denoted with the °symbol. For example, an
angle may measure 45°.
PROTRACTOR -A tool that is used to measure angles.
3

4. NAMINGANGLE
To name an angle, we name any point on one ray,
then the vertex, and then any point on the other ray
We may also name this angle only by the single letter of the
vertex, for example <B.
4

5. 5
TYPEOFANGLE

6. If the angle is not exactly to the next degree it can be expressed
as a decimal(most common in math) or in degrees, minutes and
seconds (common in surveying and some navigation).
1 degree = 60 minutes1 minute = 60 seconds
= 25°48'30"
degrees
minutes
seconds
Let's convert the
seconds to
minutes
30" "60
'1
 = 0.5'
6
Angle measurements
= 25°48'30"
48.5' '60
1
 = .808°
= 25°48.5'
= 25.808°


7. initial side
radius of circle isr
r
r
arc length is
also rr
This angle measures
1 radian
Givenacircleofradiusrwiththevertexofanangleasthe
centerofthecircle,ifthearclengthformedbyinterceptingthe
circlewiththesidesoftheangleisthesamelengthasthe
radiusr,theanglemeasuresoneradian.
ANOTHERWAYTOMEASUREANGLESISUSING
WHATISCALLEDRADIANS.
7

8. arc lengthradiusmeasure of angle
important: angle measure
must be in radians to use
formula!
Find the arc length if we have a circle with a radius of 3
meters and central angle of 0.52 radian.
3
= 0.52
arc length to find is in black
s= r30.52= 1.56 m
What if we have the measure of the angle in degrees? We
can't use the formula until we convert to radians, but how?
s= r
ARCLENGTHSOFACIRCLEISFOUNDWITHTHE
FOLLOWINGFORMULA:
8

9. conversion from degrees to radians
Let's start with
the arc length
formula
s= r
If we look at one revolution
around the circle, the arc
length would be the
circumference. Recall that
circumference of a circle is
2r
2r= r
cancel the r's
This tells us that the
radian measure all the
way around is 2. All the
way around in degrees is
360°.
2= 
2 radians = 360°
9
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180°
To convert degree to radian:

10. It is customary to use small letters in the Greek alphabet
to symbolize angle measurement.





alpha beta gamma
theta
phi
delta
GREEKSIGNS
10

11. Introduction
▪The Theodolite is the most precise instrument designed
for the measurement of horizontal and vertical angles
and has wide applicability in surveying.
The system of surveying in which the
angles are measured with the help of a
theodolite, is called Theodolite
surveying.
11

12. The Purposes of theodolite
The Theodolite is a most accurate surveying instrument
mainly used for :
➢Directing horizontal and vertical angles.
➢Locating points on a line.
➢Finding difference of level.
➢Finding the vertical height of an object.
➢Measuring the horizontal distance between two points.
➢Setting out grades
➢Ranging curves
➢Tachometric Survey
12

13. Theodolite Axis
1-V-V axis (Vertical axis or Rotation axis).
2-L-L axis (Plate Bubble axis).
3-Z-Z axis (Line of Sight axis).
4-H-H axis (Transit axis).
5-P.V.C. (Plan of Vertical Circle).
6-P.H.C. (Plan of Horizontal Circle).
13

14. Components of theodolite
14

15. Components of theodolite
LevelingHead: It is the lowermost part of a theodolite. It
consists of two parallel horizontal plates separated by
three levelingscrews.
15

16. Components of theodolite
Trivet
It is a circular plate having a central, threaded hole for fixing
the theodolite on the tripod stand by a wing nut. It is also
called the base plate.
Tribrach
It is a triangular plate carrying three foot screws at its ends.
Trivet
Tribrach
16

17. Components of theodolite
Telescope: the function of telescope is to provide line of
sight. The length of telescope varies from 100mm to 175mm.
Most of the theodolites have internal focusing telescope.
Vertical Axis: it is the axis of rotation of the telescope in
the horizontal plane
Horizontal Axis: It is the axis of rotation of the telescope
in the vertical plane.
17

18. Components of theodolite
Plate Bubbles
Twoplatebubblesaremountedatrightanglestoeach
otherontheuppersurfaceofthevernierplate.Onebubble
iskeptrightparalleltothehorizontalaxisofthetheodolite.
Sometimesoneplatebubbleisprovidedonthevernier
plate.Thebubblearemeant
forlevelingthisinstrument
atthetimeofmeasuringthe
horizontalangle.
18

19. Components of theodolite
Screws:
Atheodoliteinstrumenthasnumberofscrewsasits
componentparts.Theseareclassifiedintodifferenttypes
dependingontheirfunctions.
Levelling Screws
Clamp Screws
Tangent Screws
19

20. Components of theodolite
Leveling Screws:
These are present in the leveling head of a theodolite in
between trivet and tribrach.
These screws are used for leveling the instrument i.e., to
make plate level axis truly horizontal.
Levelling screws
20

21. Components of theodolite
Clampscrews:Theseareusedtofixthepartsofa
theodolitewithwhichtheseareattached.
VerticalplateClampScrew:Itisusedtoclampthe
telescopeinanyplaneandhenceatanydesiredvertical
angle.
HorizontalplateClampScrew:itisusedtofixedthe
horizontalcircle,and,thus,theinstrumentcannotberotated
horizontally.
TangentScrews:Witheachclampingscrew,thereisa
tangentscrewpresentintheinstrumenttoprovidefine
movement.Thetangentscrewsworkonlyafteritsclamping
screwsgettightened.
21

22. Components of theodolite
Levelling screws
Horizontal plate Clamp Screw
Tangent Screws
Vertical plate Clamp Screw
22

23. Components of theodolite
Optical plummet of theodolite: it is a small piece of
optical lenseto see the peg station under the instrument. it
is alosuse to collinear vertical axis of the instrument with
the station peg.
Optical plummet
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24. Temporary Adjustment
Temporary Adjustment
Ateachstationpoint,beforetakinganyobservation,itis
requiredtocarryoutsomeoperationsinsequence.The
setofoperationsthosearerequiredtobedoneonan
instrumentinordertomakeitreadyfortaking
observationisknownastemporaryadjustment.
Temporaryadjustmentofaverniertheodoliteconsistsof
followingoperations:
➢Setting,
➢Centring,
➢Leveling
➢Focussing.
24

25. Definitions
Face left:
Face left observation while taking the reading if the vertical
circle is towards the left of the observer, it is called face left
observation.
Face Right:
Face right observation –while taking
readings if the vertical circle is towards the
right of the observer then it is called face
right observation (this condition is also
called telescope inverted condition)
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26. Definitions
Changing the face
The operation of bringing the vertical circle from left to right
or vice versa is called changing the face.
Swinging the telescope:
The process of rotating the telescope about vertical axis is
called swinging telescope.
A set of observations:
Finding of horizontal observation once with face right
observation and other with face left observation is called
one set of observation.
26

27. Measuring Horizontal Angle
There are three methods of measuring
horizontal angles:
i) Ordinary Method.
ii) Repetition Method.
iii) Reiteration Method.
27

28. Measuring Horizontal Angle
i)Ordinary Method. To measure horizontal angle:
1-Set up the theodolite at station point O.
Direct telescope to point Aand set the horizontal angle to the
zero or 360°. Tighten the upper clamp.
2-Turn the instrument clockwise and direct the telescope
towards Band read the horizontal B and record both the
readings.
3-The reading angles at Bgives the
value of the angle AOBdirectly.
A B
O
28

29. Measuring Horizontal Angle
4-Change the face of the instrument and repeat the whole
process. The mean of the two readings gives the second
value of the angle AOBwhich should be approximately or
exactly equal to the previous value.
5-The mean of the two values of the angle AOB,one with
face left and the other with face right ,gives the required
angle free from all instrumental errors.
A B
O
HORIZONTAL ANGLE AOB
29

30. Measuring Horizontal Angle
ii) Repetition Method.
This method is used for very accurate work.
The No. of repetitions made usually in this method is
six, three with the face left and three with the face right
.In this way ,angles can be measured to a finer degree of
accuracy than that obtainable with the least count of the
Vernier.
30

31. Measuring Horizontal Angle
To measure horizontal angle by repetitions:-
1-Set up the theodolite at starting point O.
2-Measure The horizontal angle AOB.
3-Loosen the lower clamp and turn the telescope clock-wise
until the object (A) is sighted again. Bisect B accurately by
using the upper tangent screw.
Angle AOB=
AccumulatedAngle
NoofReading
31

32. Measuring Horizontal Angle
iii) Reiteration Method
It is generally preferred when several angles are to be
measured at a particular station.
This method consists in measuring several
angles successively and finally closing the
Horizon at the starting point.
The final reading of the pointA
should be same as its initial reading.
32

33. Measuring Horizontal Angle
Procedure
Suppose it is required to measure the angles AOB,BOC
and COD. Then to measure these angles by repetition
method :
1-Set up the instrument over station point O.
2-Direct the telescope towards point A
which is known as referring object.
Bisect it accurately and check the
reading as 0 or 360 .
Loosen the lower clamp and turn the telescope clockwise
to sight point B exactly and read the angle.
33

34. Measuring Horizontal Angle
3-Similarly bisect C & D successively and read both. each
bisection, find the value of the angle BOCand COD.
4-Finally close the horizon by sighting towards the
referring object (point A).
5-The direction A should now read 360°. If not notedown
the error .This error occurs due to slip etc.
6-If the error is small, it is equally distributed among the
several angles .If large the readings should be discarded
and a new set of readings be taken.
34

35. Measuring Vertical Angle
Vertical Angle :
A vertical angle is an angle between the inclined line of
sight and the horizontal. It may be an angle of elevation or
depression according as the object is above or below the
horizontal plane.
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36. Measuring Vertical Angle
Measuring Vertical angles
Face Left
V-angle= 90-Zenith angle
Face Right
V-angle= Zenith angle-270
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