Theodolite Survey basic in civil engineering.ppt

theodolite instrument uses and parts and methods to measure horizontal and vertical angles during surveying

1. THEODOLITE SURVEYING

2. THEODOLITE SURVEYING
THEODOLITE SURVEYING
Thesystemofsurveyinginwhichtheanglesare
measuredwiththehelpofatheodolite,iscalled
Theodolitesurveying.

3. THEODOLITE SURVEYING
THEODOLITE
TheTheodoliteisamostaccuratesurveying
instrumentmainlyusedfor:
•Measuringhorizontalandverticalangles.
•Locatingpointsonaline.
•Prolongingsurveylines.
•Findingdifferenceoflevel.
•Settingoutgrades
•Rangingcurves
•TacheometricSurvey

4. THEODOLITE SURVEYING
TRANSIT VERNIER THEODOLITE
THEODOLITE SURVEYING

5. THEODOLITE SURVEYING
CLASSIFICATION OF THEODOLITES
Theodolitesmaybeclassifiedas;
A.
i)TransitTheodolite.
ii)NonTransitTheodolite.
B.
i)VernierTheodolites.
ii)MicrometerTheodolites.

6. THEODOLITE SURVEYING
CLASSIFICATION OF THEODOLITES
A.TransitTheodolite:Atheodoliteiscalledatransit
theodolitewhenitstelescopecanbetransitedi.e
revolvedthroughacompleterevolutionaboutits
horizontalaxisintheverticalplane,whereasina-
Non-Transittype,thetelescopecannotbe
transited.Theyareinferiorinutilityandhavenow
becomeobsolete.

7. THEODOLITE SURVEYING
CLASSIFICATION OF THEODOLITES
B.VernierTheodolite:Forreadingthegraduated
circleifverniersareused,thetheodoliteiscalledasa
VernierTheodolite.
Whereas,ifamicrometerisprovidedtoread
thegraduatedcirclethesameiscalledasa
MicrometerTheodolite.
Verniertypetheodolitesarecommonlyused.

8. THEODOLITE SURVEYING
DESCRIPTION OF A
TRANSIT VERNIER THEODOLITE
ATransitverniertheodoliteessentiallyconsistofthe
following:
1.LevellingHead. 6.T-Frame.
2.LowerCircularPlate.7.Plumb–bob.
3.UpperPlate. 8.TripodStand.
4.Telescope.
5.VernierScale.

9. THEODOLITE SURVEYING
ADJUSTMENT OF A THEODOLITE
The adjustments of a theodolite are of two kinds :-
1. Permanent Adjustments.
2. Temporary Adjustments.
1)Permanentadjustments:Thepermanent
adjustmentsaremadetoestablishtherelationship
betweenthefundamentallinesofthetheodoliteand,
oncemade,theylastforalongtime.Theyareessential
fortheaccuracyofobservations.

10. THEODOLITE SURVEYING
ADJUSTMENT OF A THEODOLITE
1.Permanentadjustments: Thepermanent
adjustmentsincaseofatransittheodolitesare:-
i)AdjustmentofHorizontalPlateLevels.Theaxisof
theplatelevelsmustbeperpendiculartothevertical
axis.
ii)CollimationAdjustment.Thelineofcollimation
shouldcoincidewiththeaxisofthetelescopeand
theaxisoftheobjectiveslideandshouldbeatright
anglestothehorizontalaxis.
iii)Horizontalaxisadjustment.Thehorizontalaxis
mustbeperpendiculartotheverticalaxis.

11. THEODOLITE SURVEYING
ADJUSTMENT OF A THEODOLITE
iv)AdjustmentofTelescopeLevelortheAltitudeLevel
PlateLevels.Theaxisofthetelescopelevelsorthe
altitudelevelmustbeparalleltothelineof
collimation.
v)VerticalCircleIndexAdjustment.Thevertical
circleverniermustreadzerowhenthelineof
collimationishorizontal.

12. THEODOLITE SURVEYING
ADJUSTMENT OF A THEODOLITE
2.TemporaryAdjustment
Thetemporaryadjustmentsaremadeateachset
upoftheinstrumentbeforewestarttaking
observationswiththeinstrument.Therearethree
temporaryadjustmentsofatheodolite:-
i)Centering.
ii)Levelling.
iii)Focussing.

13. THEODOLITE SURVEYING
MEASUREMENT OF HORIZONTAL ANGLES :
Therearetwomethodsofmeasuringhorizontal
angles:-
i)RepetitionMethod.
ii)ReiterationMethod.

14. THEODOLITE SURVEYING
PROLONGING A STRAIGHT A LINE
TherearetwomethodsofprolongingagivenlinesuchasAB
(1)Foresightmethod,and(2)BackSightMethod
Fig.
(1)Fore Sight Method. As shown in the fig. below
A B C D Z
i)Set up the theodolite atAand level it accurately .Bisect the
point b correctly. Establish a pointCin the line beyondB
approximately by looking over the top of the telescope and
accurately by sighting through the telescope.
ii)Shift the instrument toB,take a fore sight onCand establish
a pointDin line beyondC.
iii)Repeat the process until the last pointZis reached.

15. THEODOLITE SURVEYING
PROLONGING A STRAIGHT A LINE
(2) Back Sight Method. As shown in the fig. below
A B C D Z
i)Set up the instrument atBand level it accurately .
ii) Take a back sight on A.
iii)Tightentheupperandlowerclamps,transitthetelescope
andestablishapointCinthelinebeyondB.
iv)ShiftthetheodolitetoC,backsightonBtransitthetelescope
andestablishapointDinlinebeyondC.Repeattheprocess
untilthelastpoint(Z)isestablished.
C’
D’

16. THEODOLITE SURVEYING
PROLONGING A STRAIGHT A LINE
(2) Back Sight Method.(contd.) As shown in the fig. below
A B C D Z
Nowiftheinstrumentisinadjustment,thepoints
A,B,C,DandZwillbeinoneline,whichisstraightbutif
itisnotinadjustmenti.e.lineofcollimationisnot
perpendiculartothehorizontalaxis,thenC’,D’andZ’
willnotbeinastraightline.
C’
D’

17. Method of traversing
–Included angle method
–Deflection angle method
–Fast angle (or magnetic bearing method)

18. Computation of latitude and departure
•Latitude of a line is the distances measured parallel
to the north south of the North-South direction
•Departure of the line is the distance measured
parallel to the east-west direction

19. Computing latitude and departure

20. Sources of errors in theodolite
•Instrumental errors
–Non adjustment of plate bubble
–Line of collimation not being
perpendicular to horizontal axis
–Horizontal axis not being perpendicular
to vertical axis
–Line of collimation not being parallel to
axis of telescope
–Eccentricity of inner and outer axes
–Graduation not being uniform
–Verniers being eccentric

21. •. Personal errors
•Natural errors
–High temperature causes error due to irregular refraction.
–High winds cause vibration in the instrument, and this may lead to wrong
readings on verniers
•Closing error

22. Balancing of traverse
1.Bowditch’s rule:
Total error is distributed in proportion to the lengths of the traverse legs.