Compass surveying involves measuring directions with a compass and distances with a chain or tape. It is used when the area is large, undulating, or has many details. There are two types of compasses used - the prismatic compass and surveyor's compass. The prismatic compass measures bearings in degrees from 0-360 while the surveyor's compass measures in quadrants from 0-90. Traversing involves connecting lines and measuring bearings and distances to determine positions without triangulation. Bearings can be true, magnetic, grid, or arbitrary and are expressed using the whole circle bearing or quadrantal bearing systems. Examples are provided to demonstrate converting between systems and calculating interior angles of traverses.

1. Compass Surveying
By Warish Khan Sukediya
Ph.D Scholar
Govt Polytechnic Haryana

2. What isCompass?
• ACompassisaninstrumentcontainingamagnetizedpointerwhich showsthe
directionofmagneticnorthandbearingsfromit.
Typesof Compass:
• PrismaticCompass
• Surveyor’sCompass
• APrismaticcompassisanavigationand surveying
instrumentwhichisextensivelyused fordetermining
course,waypointsand direction,andforcalculating
bearingsofsurvey linesandincludedanglesbetween
them.
•ASurveyor'scompass,isaninstrumentused in
surveyingtomeasurehorizontalangles.It was
supersededbythetheodoliteintheearly 19th
century.

3. PrismaticCompass Surveyors'Compass

4. PrismaticCompass Surveyor’sCompass
TheGraduatedringattachedto the
magneticneedle.
TheGraduatedringandneedlearefree to
moveindependentlywrt eachother
Graduatedringremainsstationarywhile boxis
prismandobjectvanerotatesas theringattach
withneedleisnotattach withthebox
Graduatedringrotateswithrotationof box
,eyevane&objectvaneastheringisattach withthe
boxofthecompass&onlyneedle remains
stationary
Prismisprovidedtotakereading Thegraduatedringisgraduatedwithejected figures
andnoprismisprovidedtotakethe reading
Graduationaremarked0to360in
clockwisedirection
Graduationsaremarked0to90ineach
quadrant
Tripoidmayormaynotbe provided. Theinstrumentcannotbeusedwithout tripoid
It measuresorgivesWCBofaline It measuresorgivesQ.B.ofaline.

5. CompassSurveying
•ChainSurveyingcanbeusedwhenthe Area
tobesurveyediscomparatively smallandis
fairlyflat.
•Butwhentheareaislarge,undulated and
crowdedwithmanydetails,
triangulation(whichistheprincipleof chain
survey)isnotpossible.Insuchan area,the
methodoftraversingis adopted.

6. Principleof CompassSurveying:
•ThePrincipleofcompasssurveyisTraversing;whichinvolvesaseriesof connected
linesthemagneticbearingofthelinesaremeasuredby prismaticcompassandthe
distance(lengths)aremeasuredby chain.
• Suchsurveydoesnotrequiretheformulationofanetworkof triangle.
•Compasssurveyingisrecommendedwhentheareaislarge,undulating and
crowdedwithmanydetails.
•Compasssurveyingisnotrecommendedforareaswherelocal attractionis
suspectedduetothepresenceofmagneticsubstanceslike steelstructures,ironore
deposits,electriccablesconveyingcurrents.

7. • In traversing , the frame work consist of connected lines.
• The length are measured by a chain or a tape and the
direction measured by angle measuring instruments.
• Hence in compass surveying direction of survey lines
are determined with a compass and the length of the
lines are measured with a tape or a chain. This process is
known as compass traversing.
Traversing

8. TypesofBearing:-
The bearing of a line is the horizontal angle which it makes
with a reference line(meridian).
there are four type of bearings :-
1) True Bearing: The true bearing of a line is the horizontal
angle between the true meridian and the survey line.The
true bearing is measured from the true north in the
clockwise direction.
2)Magnetic Bearing: the magnetic bearing of a line is the
horizontal angle which the line makes with the magnetic north.
3)Grid Bearing: The grid bearing of a line is the horizontal
angle which the line makes with the grid meridian.
4)Arbitrary Bearing: The arbitrary baring of a line is the
horizontal angle which the line makes with the arbitrary
meridian.

9. BEARINGS
TRUE
MERIDIAN
MAGNETIC
MERIDIAN
TRUEBEARING
MAGNETIC
BEARING
A
B
TN
MN

10. The bearing are designated in the following two system:-
1) Whole Circle Bearing System.(W.C.B)
2) Quadrantal Bearing System.(Q.B)
Measurement of Bearings:

11. Whole Circle Bearing System.(W.C.B)
•The bearing of a line measured with respect to magnetic meridian
in clockwise direction is called magnetic bearing and its value
varies between 0ᴼto 360ᴼ.
•The quadrant start from north an progress in a clockwise direction
as the first quadrant is 0ᴼto 90ᴼin clockwise direction , 2nd 90ᴼto
180ᴼ, 3rd 180ᴼto 270ᴼ,and up to 360ᴼis 4th one.
Quadrantal bearing system(Q.B.)
•In this system, the bearing of survey lines are
measured wrt to north line or south line which ever
is the nearest to the given survey line and either in
clockwise direction or in anti clockwise direction

12. •Whenthewholecirclebearingisconvertedinto
Quadrantalbearing,it istermedas“REDUCEDBEARING”. Thus,
thereducedbearingissimilartotheQuadrantal bearing.
•Itsvaluesliesbetween0ᴼto90ᴼ,butthequadrantshould be
mentionedforproperdesignation.
Reducedbearing (R.B)
W.C.BOFANY
LINE
QUADRANTIN
WHICHIT LIES
RULESFOR
CONVERSI
ON
QUADRANT
0TO90 I RB=WCB N-E
90TO180 II RB=180-WCB S-E
180TO270 III RB=WCB-180ᴼ S-W
270TO360 IV RB=360ᴼ-WCB N-W

13. Forebearing andBack bearing
Thebearingofalinemeasuredintheforwarddirectionofthesurvey
linesiscalledthe‘forebearing’(F.B.)ofthatline.
Thebearingofalinemeasuredindirectionbackwardtothedirectionof theprogress
ofsurveyiscalledthe‘backbearing’(B.B.)oftheline.

14. How to read Bearing Readings

15. Typesof Meridians:
•Magneticmeridian:-Thedirectionshownbyafreely suspended
needlewhichismagnetisedandbalanced properlywithout
influencedbyotherfactorsisknownas magneticmeridian.
•Truemeridian:-Truemeridianisthelinewhichpassage throughthe
truenorthandsouth.Thetruemeridianatanypointcanbe
determinatebyeitherobservingthebearingof thesunat12noonor
bysun’s shadow.
•Arbitrarymeridian:-Incaseofsmallworkorinplaceswere true
meridianormagneticmeridiancannotbedetermined, thenanydirection
ofprominentobjectistakenasareference directioncalledasarbitrary
meridian.

16. Exampleof WCBinto Reduced
Bearings:-
• ConvertthefollowingWCBintoRB

19. • S43 °15’E

20. Example:- 1

21. Note :- If FB>180thensubtractionisrequired Andif
FB<180thenadditionisrequired

22. Example2 :-
ThefollowingbearingsweretakenofaclosedtraverseABCD.
Line FB BB
AB 45°00’ 225°00’
BC 123°30’ 303°00’
CD 181°00’ 1°00’
DA 289°00’ 109°00’
Calculatetheinteriorangelsofthetraverse.

23. Station Line FB Line BB DiffofFB&
BB
Exterio
r
Angle
Interior
Angle
A AB 45°00’ DA 109°00’ 64°00’ 64°00’
B BC 123°3’ AB 225°00’ 101°00’ 101°30’
C CD 181°0’ BC 303°30’ 122°30’ 122°30’
D DA 289°0’ CD 1°00’ 288° 288° 72°00’
I
nterior angle A =BB of DA – FB of AB
Interior angle B =BB of AB – FB of BC
Interior angle C =BB of BC – FB of CD
ExteriorangleD=FBofDA– BBofCD
SotheInteriorangleD=360°– InteriorangleD
Sumofangles=64°+101°30’+122°30’+72°
=360°
Check=(2N– 4)* 90°
=(2*4– 4)*90°
=360°

24. Example3 :- TheDetailsofobservedbearingsarementionedbelow. Findout
theincludedanglesandcorrecttheanglesif neededtobe corrected.
LINE FB BB
AB 20°30’ 200°00’
BC 110°00’ 290°30’
CD 195°00’ 15°00’
DA 286°30’ 106°00’

25. Station Line FB Lin
e
BB Diff.ofFB
&BB
Exterior
Angle
Interior
Angle
A AB 20°30’ DA 106°0’ 85°30’ 85°30’
B BC 110°00’ AB 200°00’ 90°00’ 90°00’
C CD 195°00’ BC 290°30’ 95°30’ 95°30’
D DA 286°30’ CD 15°00’ 271°30’ 271°30’ 88°30’
Sum=359°30’
Interior angle A =BB of DA – FB of AB
Interior angle B =BB of AB – FB of BC
Interior angle C =BB of BC – FB of CD
ExteriorangleD=FBofDA– BBofCD
SotheInteriorangleD=360°– InteriorangleD
Sumofangles=85°30’+90°00’+95°30’+88°30’=359°30’
Check=(2N– 4)* 90°
=(2*4– 4)*90°
=360°
∴TotalError=359°30’– 360°=–30°

26. TotalCorrection=+30’∴
∴Correctionperangle=+30’/4=+7’30”
Correctedvalue:-
Angle Calculatedvalue Correction Correctedincluded
Angle
A 85°30’ +7’30” 85°37’30”
B 90°00’ +7’30” 90°07’30”
C 95°30’ +7’30” 95°37’30”
D 88°30’ +7’30” 88°37’30”
Sum 359°30’ +30’00” 360°00’00”

27. THANK YOU
Dr. Khan