Measuring of Horizontal angle Practical Part

Surveying Engineering
Plane and Applied surveying 2
Theodolite practical part 1
Report number(1)
Report name: Setting up Theodolite Instrument Measuring Horizontal and Vertical Angle.
Apparatus:
Theodolite Instrument 1 No.
Tripod 1 No.
Pin 3 Nos.
Tape 1 No.
Range pole 2 Nos.
Object :
1. To perform temporary adjustment of theodolite instrument
2. Measuring of Horizontal angle H.A Face Left (F.L) and face right(F.R) .
3. Measuring of Vertical angle V.A Face Left (F.L) and face right(F.R)
Measuring Horizontal Angle
There are three methods of measuring horizontal angles:
i) Ordinary Method
ii) Repetition Method.
iii) Reiteration Method.
Angular measurement :
Angular measurement is made using surveying instruments which measure
both horizontally and vertically in degrees. Degrees are sexagesimal units which are subdivided into minutes and seconds in exactly the same manner as time.
Calculation and Measuring Horizontal Angle
i)Ordinary Method. To measure horizontal angle:
1-Set up the theodolite at station point ( O)
Direct telescope to point A and set the horizontal angle to the zero or 360°.
2-Turn the instrument clockwise and direct the telescope towards B and read the horizontal B and record both the readings.
3-The reading angles at B gives the
value of the angle AOB directly.
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 AOB which 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.
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 .
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 point A should be same as its initial reading.
*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.
Prepared by:
Asst. Prof. Salar K.Hussein
Mr. Kamal Y.Abdullah
Asst.Lecturer. Dilveen H. Omar
Erbil Polytechnic University
Technical Engineering College
Civil Engineering Department

1. 1
Erbil Polytechnic University
Technical Engineering College
Civil Engineering Department
Surveying Engineering
Plane and Applied surveying 2
Theodolite practical part 1

2. Report number(1)
Report name: Setting up Theodolite Instrument Measuring Horizontal and Vertical Angle.
Apparatus:
Theodolite Instrument 1 No.
Tripod1 No.
Pin3 Nos.
Tape1 No.
Range pole 2 Nos.
Object :
1. To perform temporary adjustment of theodolite instrument
2. Measuring of Horizontal angle H.A Face Left (F.L) and face right(F.R) .
3. Measuring of Vertical angle V.A Face Left (F.L) and face right(F.R)
2

3. Data Sheet &Table
AV.H.AF.RF.LPoint St
21B
?A
43C
A
C

4. Measuring Horizontal Angle
There are three methods of measuring horizontal angles:
i) Ordinary Method
ii) Repetition Method.
iii) Reiteration Method.
4

5. 5
Angular measurement:
Angular measurement is made using surveying instruments which measure
both horizontally and vertically in degrees. Degrees are sexagesimal units which
are subdivided into minutes and seconds in exactly the same manner as time.
q= 25°48'30"

6. Calculation and 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°.
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.
6
AB
O

7. 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 meanof 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.
7
AB
O
HORIZONTAL ANGLE AOB

8. Measuring Horizontal Angle
ii) Repetition Method.
Thismethodisusedforveryaccuratework.
TheNo.ofrepetitionsmadeusuallyinthismethodis
six,threewiththefaceleftandthreewiththefaceright
.Inthisway,anglescanbemeasuredtoafinerdegreeof
accuracy.
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9. Measuring Horizontal Angle
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10. Measuring Horizontal Angle
iii)ReiterationMethod
Itisgenerallypreferredwhenseveralanglesaretobe
measuredataparticularstation.
Thismethodconsistsinmeasuringseveral
anglessuccessivelyandfinallyclosingthe
Horizonatthestartingpoint.
ThefinalreadingofthepointA
shouldbesameasitsinitialreading.
10

11. 11

12. Measurement of horizontal angles:
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13. 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 aboveor belowthe horizontal plane.
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14. Measuring Vertical Angle
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Measuring Vertical angles
Face Left
V-angle= 90-Zenith angle
Face Right
V-angle= Zenith angle-270

15. Measurement of Vertical angles:
F.L= 90˚-Zenith angle.
F.R= Zenith angle -270˚
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