1. Deline: Compass suneying. What are the obiects of compass surveying?

Compass surveying is the type of surveying in which the direction of the survey lines are

measured with a compass and the length ofthe survey lines are measured with a tape or chain intufield

2 Wrt tc nemes of the instruments used in chain surveying,

GI I*unents for the direct measurement of directions:l. Surveyor's compass.

2. Prismatic compass.

S[nstruments for the measurement of angles:

efine: (a). True meridian and bearing.True meridian: r

The line or plane passing through the geographical ].lorth Pole, South Pole and any point on the

surface of the "urth,

is kng*t us true metidian or geographical meridian. True meridian at a point

is constant.

True bearing:The angle between the true meridian and a survey line is known as true bearing or Azimuth of

the line.

(b), Magnetic meridian and Bearing.

Magneljc meridian :

Magn6tic meridian at a point is the direction

and unaffected magnetic needle at that point.

Magnetic Bearing:The angle between the magnetic meridian and a survey line

bearing .of the line. lt changes with time'

is known as magnetic bearing or

{Wh^t do yo, understand by Whole circle bearing and quadrantal bearing of a line?

In Whole circle bearing system (WCB), the bearing of the line is measured

with magnetic north in clockwise direction. It varies frbm 0' to 360".

In quadrantal bearing system (Q.B or R.B) the bearing of the line is measured eastward or

westward from north or south, whichever is nearer. The directions can be either clockwise or

anticlockwise. It varies from 0' to 90'.

indicated by freely suspended, properly balanced

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l. Sextant.

2. Theodofite.

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/Cowartthewhole circle bearing into $duced bearingr 50" 176o' 210o' 232ot 150" 76o'

't }l0" ,242".Whole circle bearing (WCB)

Reduced bearing (RB)

50"N 50'E.176'S (180'- 176") E = s 40 E

210' s (210' - 180') w = s 30' w232" S Q32" -180") w = s 52" wl5o' s (180" - 150) E = s 30" E

76\ 76" E

310'N (360" - 310') w =N 50'w242' S (242"- 180) w : s 62''w

6.DifferentiatebetweenPrismaticcomp'ssandSurveyor'scompasswithreferencetoreading and triPod.

,/.Theforebetring of a line PQ is N 28" W. What is its backbearilq?.-In

quadrantal bearing (RB) system, the FB and BB are numerically equal but

the quadrants are just oPPosite.

The FB of a line PQ is N 28" W,

Then its BB is S 28o E.

(. Definel Fore and Back bearing.

Tle bearing ofa line is measured in the {irection of the progress of the survey is called the fore

bearing of the (FB) line.

The biaring of a line is measured in the direction opposite to the survey is called the back

bearing of the (BB) line.

BB = FB + 180". (FB greater than 1 80o, use - sign)

(FB smaller than 180o, use + sign)

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Surveyor's comPassPrismatic compass

(i). The reading is taken bY

directly seeing through the toP ofthe slass.(ii).lishting and reading taking

cannot be done simultaneouslY

from one position of the

1i;Jhe reading is taken with a

tretp of prism Provided at the eYe

slit.(ii). Sighting and reading takingcan be done simultaneouslY fromone position of the observer.

Reading

The-instrument cannot be used

without a triPod.Tripod may or may not beprovided.

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ffIte fore bearing of tine AB is 155025'20". Identify the back bearing of the tine AB inquadrantal system,The fore bearing ofline AB = 155025,20,,.The back bearing of line AB , BB = FB + 1 80.= 155'25'20" + 18'= 33s'2s'20" (wcB)= N (360' - 335'25'20) w: N 24'34', 40" W

10. Deline and distinguish between magnetic dip and magnetic declination.

11. The magnetic bearing of a line is 48024'. Calculate the true bearing if the magneticdeclinations are 5038' East and 50 38, West,True bearing = \,lagnetic bearing + Eastem magretil declination= 48"24', + 50'38'= 54'02'.True bearing = \{agnetic bearing - Westem magnetic declination= 48"24' - 50'39'= 42"46'.

12. The magnetic berring of a liDe is S 28o30' E. Caleulate the true bearing if themagnetic declinotions are 50"38' Eait and 50o 38, West,Convert tle reduced bearing into Whole circle bearing.Magnetic bearing = S 28"30' E. (RB)= 180'- 28"30'= l5l'30' .

True bearing = Magnetic bearing + Eastem magnitic declination= l5l'30'+ 70"30'= 159'00'. (wcB)= s(1801159"00',)E (RB)

= s 21"E.

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Maenetlc di Masnetic declinationDue to the magnetic influence of the earth, theneedle does not remain in thebalanced position. This inclination of theneedle with the horizontal is known as the dipof the magnetic needle. To balance. the dip ofthe needle, a rider (brass or silver coil) isprovided along with it.

The magnetic meridian of a place is variableone due to some local attractiveforces. Therefore, tle true meridian and themagnetic meridian at a place do not coincide.The horizontal angle between the magneticmeridian and the true metidian is known asmagnetic declination

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True bearing : Magnetic bearing ,' Westem magnetic declination

= 151"30'- 70'50'= 144"00',. (wcB)= S(180'-144"00')E (RB)

= S 36"8.

.{3. What is local attraction? What are the sources of local attractions?

Local attraction is a.term used to denote any influence, such as magnetic

substances, which prevents the needle from pointing to the magnetic north iu a given

locality. The sources oflocal attractions are : magnetite in the ground' wire carrying

electric cunent, steel structures, rails, underground iron pipes, chain etc.,

14. Distinguish between closed traverse and open traverse.

15. What is plane table surveying? When is it preferred? Write its principle.Plane tabling is the graphical method of surveying in which the fieldobservations and plotting proceed simultaneously.It is mainly suitable for filling the interior {etails between the control stationsand also in magr.etic areas. I

The main principle ofplane table surveying is that the lines joining thepoints on the plane table are made to lie parallel to the corresponding lines joining thepoints on the ground while working at each station.

SI.No. Closed traverse Open traverse

t. When the lines form a circuit, whichends at the starting point, it is knownas closed traverse

If the circuit ends elsewhere, it isknown as open ffaverse

2. It is suitable for locating theboundaries of lakes, woods etc,. ,

It is suitable for suveying a longnarrow strip of land required forrcad canal etc,.

3. Check:Sum of interior angles = (2n - 4) 90Sum of exterior angles = (2n +4) 90Where, n= number of sides ofthetraverse.

No direct check on angularmeasurements.

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16, Name four methods of plane surveying.1 . Radiation2 . Intersection.

3. Traversing4. Resection.(i). Resection after orientation by compass.

(ii). Resection after orientation by back sighting.(iii). Resection after orientation by three point problqm.

(iv). Resection after orientation by two point problerfi

a. Mechanical method.(Tracing paper method)b. Graphical method. ( Bessel's method)c. Lehmanos method. (Trial and error method)

17. When a three- point problem resorted to in plane table surieying?It is the method of orientation when the table occupies a position not yetlocated on the drawing sheet. This method is employed when dudng surveying the surveyor feels

that some important details can be plbtted easily by choosing any stations.

18, State the First and second Lehman's rule.First rule: The distance of the point "p" (position of plane table on the drawing sheet) to be

fixed from each rays Aa (paper a, to $ound A), Bb (paper,b to ground B) and Cc (paper c, to

ground C) ii pr6portional to the respective distances of the stations A, B and C from the ground

station P.

Second rule: While looking towards the stations the point "p" to be fixed, willbe either to the left or to the right ofeach ofthe rays.

19. What are the Advantages of plane table sun$ing?1 , It is useful in magnetic areas.

2. It is cheaper than the theodolite surveying.

3. It is most suitable for small-scale maps.

4. The surveyor can compare plotted work with the actual features.

5. No skill is required .

20. Name some of the errors in plane tabling.1. Instrumental error.

2. Enors of plotting

3. Errors due to manipulation and sighting.

1. Non horizontality ofthe board.

2. Defective sighting.

3. Defective orientation.

4. Movement of board between sights. I

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l.Whatismagneticmeridian? lttov lOet- Wo,The directions shown by a magretic needle without beig affected by magnetic substance, when

the needle is suspended freely and balanced properly is known as the magnetic meridian'

- - ^ a\2; What is whote.circle bearingr (rcn.l lg 4a - 2ool2

The beariag of a line measured clockwise from the north pole towards the line is known as whole

circle bearirrg of that line. The whole circle bearing ofa line is obtained by prismatic compass.

The bearing may have a value between 0 to 360.

\3. What is foresight? (nt ot I 96 c 1 2'' o 1 )It is the last staff reading taken on a point in any setup of the levelling instrument and indicates

the shifting of the instrument.\

4. What is a backsight? (tto't lo,c - zo o 1)It is the first staff reading taken on a point of known elevation in any setup of the levelling

instrument.

5. Differentiate between magnetic dectination and dip. @ov lo e c '- 2o oZJ

Refer Question 10 in previous section

6. How is graduations marked on prismatic compass? Why? ( ragI ll,e - LOol)"UGraduations are numbered clockwise from zero at the south end,90 at the west,l80 at the north

and 270 at the east.The graduation figures are written inverted as they could be seen in upright

position while viewing through the prism.

l-7. How surveyor's compass is graduated? (lo..t lOec-too1)In surveyor's compass the graduated dial is in qkarants and fixed to the box.The readings are

taken through naked eyes only.Graduation are numbered 0 to 90 in each ofthe four quadrant.

Zero at north and south and 90 at E and w.The graduation figures are written in uprightposition.

8. What is local attraction?

Refer Quesdtion 13 in previous section Do

v lOe , -a ooll

9. What are the gources of local attraction? fu"' loec

The materials which may influence magnetic action are presents of :

1 . Magnetic rocks2. Iron ore deposits3. Steel structwe4. Railways5. Iron lamp post6. Transmission powers

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10. Define (a) True bearing (b) Magnetic bearinS,[aaz f t,t'u e ' 2o,,4J

Refer Question 3 in previous section

ll,Definethefollowingterms: ft,ex I P*!, ' raot)

Refer Question 3 in previous section,

Find the magnetic declination at a place if the magnetic bearing of the sun $5roon is (a)

i84 " (b) 350"20',

Solution :

The sun is exaotly on the true meridian at noon. Since the magnetic bearing are greater than

180u. The sun is at the south.

a. Magneticdeclination:

= 184" - 180" = 40" wb. Magrretic declination:

360'- 350'20' - 9004' E

12. Define closed trrverse by means.of a stretctr pov / oa L- to VJ

Closed traverse ( ABCDE) is one in which the last survey line (EA) is joined back to the first

station point (A) forming a polygon. Such a type of survey is more suitable for moderately large

area like lakes ,forest, building complex etc.,

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such as bunch of iron keys

work such as chain arrowI

, knife, ironbuttons itch and the

etc. may influence the correct

l. Name the possible sources oflocal attraction in a survey fieH? (r^4{1 firr,a--t,>1The materials which may infeuexe magnetic action or presence of \ q | - --' -

o Magnetic rocks

o Iron is deposited

o Railways

r Iron lamp posts

o Transmission towers

Even commonly used iron material

instrument used during the survey

bearing due to local attraction.

2. List out the various instruments used in plane table survey ( i(efl 1 n^. _f9

The instruments needed in plane table surveying are /o Plane table

o Alidade.

o Plumbing forks

o Chain

. Ranging rod

o Spirit level

r Tripod

3. What is meant by magnetic dectination? t*y / \o.-,)The horizontar angle between the magnetic r|eridian and the ,true meridian of a prace is

known as magnetic declination or declination ofthe needle.

4. Enlist the disadvantages of plane tabte surveying ( Ua, / O,e. _fyo It is not suitable in wet crimate rike rainy seasons foggy atmosphere in windy weather

and in sunny weather

. It is involved with heavy equipments and very difficult to.carry

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. The no of accessories required in survey work is more and they are likely to be lost

. It is not suitable for accurate work

o There is no flexibility for reporting of work as there is no field book and recording

available.

5. Explain merits of plane table surveyipB? (./\".t i tl^/n.r - B/o It is very much suitable for small - size surveys and to prepare small - scale maps

. As the plotting is done in the field simultaneously no field book is needed and no error in

booking occurs

. Actual feature of the gtound can be compared for accuracy and there is no room for

omitting any features

o Errors ofmeasurements and plotting cannot immediately be detected by check lines

. It is most rapid in conducting.

(*-U/ Cu^^r- -13)r Elevations & depression can be determined

. Boundaries can be established.

7. what ls the use of the trough comprsp on a plane table surveying? ( rrf rtr / $lc - t a-)

o The compass is used for orienting the plane table to magnetic north

o The compass used with plane table is a through compass in which the longer sides of the

trough are parallel and flat so that either side can be used as a ruld or laid down to

coincide with a straight line drawnlon the paper

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l.Discuss the worklng princlple of prismatic compass in detail?

A Prismatic compass consists of (i)ma8netic needle (ii)a graduated circle, and(iii)a line of sight. Acompass does not measure the angle between two lines directly, but measures the angle with reference

to a magnetic meridian.

There are two types of compass which are in use ,viz,prismatic compass and surveyor's compass.Theformer one is commonly used for rough surveys.The prismatic compass is widely used for surveys inrough traverse, wooded areas, filling in details, preliminary surveys, etc.

It is not suitable on places with magnetic rock, iron are or iron based industrial areas. it is less accurate

than a theodolite.

.PRISMATIC COMFASS.

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Parts of orismatic compass:The essentials parts of a prismatic compass are discussed below,

compass box;

It is a metallic box of 8 to 10 cm in diameter. it is provided with pivotal, a sharp, point at the centre.

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llgClgllsJeedle: The magnetic needle is an iron bar with pointers at both ends' The needle is attached

to a graduated aluminum ring.

gIedgEgllilg: The ring is graduated from O" to 360'clockwise The o' is marked at the south'go" at

the west,l8o' at the north and 270" at the east.The degrees are further subdivided in to half deSrees

and the figures are upside down.

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SiEhtinF vane and prism: The sighting vane and ihe reflecting prism are mounted diametrically opposite'

the*\ighting vane is provided with a horse hair at the centre and the vane is hinged with metal box' The

'prismhasaslghtingslitatthetopandtwoholesoneatthebottomoftheprismandtheotherattheside of the observer's eYe.

gcIEiE$gc: Red and blue glasses are provided with the prism Red to be used for sighting luminous

ob.iects at night and the blue for sight during bright day right'

Adiustable mirror: The mirror, provided with the prism, can be lowered or raised with the inclined The

mirror can be used for viewing obj€cts too low too high through reflection'

Brake oin: ln order to prevent the oscillation of the ring, a breaker pin is provided at the base of the

sight vane.

!ft!$-pblA lifting pin is provided just below the slght vane' When folded the sight vane presses the

|.,**pinandthemaBneticneedleisliftedoutofthepivotalpoint.Thisarrangementspreventsdamage,if any, to the Pivotal head.

$353eyg1: A glass covered provided at the top of the box Protects the ring from dust'

Usinq of a prismatic compass: The compass is mounted on a tripod with the an adlustable ball and

socket joint' By means of this arrangement ,the compass can be levelled quickly

gflledlEFirstthecompasshastobecenteredoverthestationwherethebearinghastobetaken.This

isdoneusingaplumbboborroughlybydroppingapieceofstonefromthecentreofcompass.lfitiscenteredproperlythetipofplumbbobwillexactlyabovethecentreofthepeSrepresentthestationordropping a small to fall on the top the peg.

'evellir,le: The second step is to be make the magnetic ring in the horizontal position and swing quite

freely.This is done by adjusting the ball and socketioint'

Observinp bearlnE: The third step ls to observe the bearing. A ranging rod is kept on the next station,

and the rod is bisected by the hair by lookinS through the slit. when the needle comes to rest, the

readinB in the ring cut by the hair line is taken, this is the bearlng of line'

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2.Explain the two point problem method of plane table surveying? (Mayrune 2009)Two point of problem consists of locating the positionlof a station occupied by the plane table by means

:,il1::H::}.,::"t]|o,["J:::""'points on *re tiera wrrose posio"*l,"'r""* on the paper.

(i)Let P and Q are well defined points on the field whose positions are plotted on the paper as p and e.Let a new station A is to be located.

(ii)An auxiliary station B is chosen at a suitable position such that it is visible from all the threepoimts.After levelling and orientation the table is clamped.

(iiilwith alidade touching P, the point p is bisected and a ray is drawn. similarly the aridade touching q,the point e is bisected and a ray is drawn. Let these rays meets at b.

(iv)With the alidade touching b, the ranging rod at A bisected and a ray is drawn. on this rineapproximately by judgment mark the position of A as a,

(v)The table is shifted and centered.on A, coinciding a, on paper above it. Necessary revelling andorientation by back sighting are done,

(vi)with the alidade touching p, the point p is bisected and a ray is drawn. if the estimation of theposition of a, is correct, it will interest at a I

(vii)with the alidade a, the point Q is bisected and a ray is drawn. This ray may intersect the ray bq atpoint q, Now triangle pq, is the error which is to be eliminated.

(viii)The alidade is placed along the line pq. A ranging rod R is fixed at same distance from the table,(ix)The alidade is placed along the line pq and the table is turned and the ranging rod at R is bisected.This is the position at which the table is said to be perfectly oriented.

(x)Now the alidade touching p and q, the points p and e are bisected and the rays are drawn tointersect at a.

(xi)This represents the exact position of the station A. Then the station A is marked on the ground usingU-folk and plumb bob.

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3,Explain briefly about three polnt problem of; (Nov/Dec 2010)

(alBessels sraohlcal methodi I

(i) Let P,Q and R are well-defined points on the field whose positlons are plotted on the drawing sheet thas p,q and r,it is required to locate a station A on the ground.

- (ii)The plane table is placed above the station A and levelled. The alidade is placed along the line rp and

the point A ii bisected and then the table is clamped.

(iiilThe alidade is placed along the line Pr and the point R is bisected and then the table is clamped. Withthe alidade centered at p,the point Q is bisected and a Ray is drawn, lets this ray interest the ray at s.

(iv)Now the alidade is placed along sq and the point q is bisected. At this position, the table is said to beperfectly oriented

Now the rays Pp, Qq and Rr drawn. These rays should meet at a which is the required point on the plan.

The point is transferred to the ground using U-folk and plumb bob.

(blTrlal and Error method:

(i) Again P,Q and R are well-defined points and A is the required station.

(il) The table ls set up the A and levelled and ortentation is done by eye judgment.

(iii) using the alidade the line pp, qq and Rr are drawn. As the orientation is based on the eye judgmentthe rays may not intersect at a point but small triangle of error may be formed.

(iv)ln order to get the point the triangle of error may be eliminated. This is done turning the tableclockwlse such that the triangle of error is elilninated.

After the elimination of the ray Pp, Qq and Rr will meet at a point a.This is the required position and thepoint a is transferred to the ground using U-folk and plum6 bob,

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4.Compare a surveyo/s compass with,a prismatic compass? ( NovlDec 2010t

Surveyo/s compass

Matnetic needle (i)The needte - is--EEad-magnetized iron bar.(ii)Moves freely over the

(ilThe needte is an-age Uai[pEmagnetized.(ii)Shows the reading on the ring.

Graduated ring The graduated card ring isattached to the needle. Thering does not rotate with theline of sight.

The graduated card is fixed to ttre boxand rotates with the line ofsight.

Graduation marls (i)The graduation--fEnumbered clockwise fromzero at the south end,go.atthe west,18o. at the northand 270' at the east.

(ii) The graduation figuresare written inverted,

(i)Graduations are numUeE-l;-t690'in each ofthe quadrant. Zero at Nand S,90'at E and W.

(ii)The traduation figures are writtenin upright position.

SiShtlng vanes (ilThe object vane c;sists;a metal vane with a verticalhair and the eye varie is asmall metal vane with slit.

(ii)Mirror is attached to the

obJect vane consists of avane with a vertical hair where as theeye vane is a metal vane with a fineslit.

(ii) No Mirror is attached to theobject vane.

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(i)The objea has to be siShted first

and then to go round to read

graduation.

(ilThe reflecting Prism€arries the sighting slit and

the sighting of the object

and reading done

simultaneously,

(iilReading taken through

Observation reading

(i)This can not be used without a

tripod.(i)Tripod may or may not be

needed. lt can be used even

by holding suitably in hand.

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5.What are the different methods of plottlng a traverse survey? (Nov/Dec 20041

Plotting;

The bearings observed during the field work should be first of all corrected. A rough plan has to be

prepared first preferably to the same scale. This helps to decide proper orientation, to arrange, to plot

deta,ils, and the overall arrangement of thefsheet. Although many methods are available, the most

generally used methods are explained below.

Parallel meridian method

First a line representing the magnetic meridian is drawn. Let us consider a closed traverse ABC0EA'

The station point is plotted.

At A, a line parallel to meridian is drawn. The line AB is drawn as per the measured bearing of the line AB

and the length ofAB marked.

At B, a line parallel to the meridlan is drawn. The length and bearing of BC is drawn similarly all the lines

are drawn.

ln the case of a closed traverse the last point should be coincide with the startlng polnt. lf it is not

coincldlng, the closing error is adjusted.

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hcluded anEles method:

The magnetic meridian is drawn.reference to the magnetic meridian.

The. included angles are computed. The first line is drawn withOther lines are drawn in sequence by drawing the incluOea aneLs.

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ln the above two methods of protting, the accuracy ofthe rocation ofstation points and theSurvey line depend on the station and lines preceding them.

Thus any error in protting of the rines and stations by bearing wifi be carried to a[ sides of the tra\and seriously affect the whole plotting E Lsr I rsu

'e drr srqgs or rne traverq. .

ln order to overcome such errors, each station points shourd be protted independentry. This approach-isfollowed in the rectangular coordinate method.

ln this method each point is plotted by its coordinates with reference to two perpendicular axles. Theseaxes are called as axes of co_ordinates.

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The point of intersection of these line is called the origin. The axis OX represents the east-west line and

oY represents the north-south llne.

5. Describe brlefly the radiatlon method of plane table surveying. (Nov/Dec 2010)

RFdlatlon method:

ln this method, the plane table is set out, on one location and various points are located by drawing

radiating rays frdrn the plane table station to each ofthe points and the actual distances to scale on the

corresponding rays.

Following is the procedure;

(i)The plane table is up on a station P, such that all the points A,B,C,D and

(iilThe north line is drawn on the riSht hand top corner of the drawing

compass.

(ililWlth the alldade touchlng point p, the ranglng roads at A,B,C,D and

drawn.

E on the grounds are visible.

sheet using through or box

E are blsected a bd rays are

(iv)The distances PA,PB,PC,PD and PE are measured by a tape or chain and the distances are plotted on

the respective rays to a suitable scale.

The radiation method is useful for surveys of small areas where in all the objects can be commanded

from a single plane table statlon. ln large-scale areas to be surveyed this method can be continued with

other methods. Using a telescoplc alidade the work can be rapidly used and will have a wider scope.

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7.What is reiteration method? When and how is it employed? (Nov/Dec ZOIO)

This is a high precision method' This method is less tedious and mostly preferred when several anglesare to be measured from a single station.

ln this method all the horizontal angles are measured successively and finally the horizon is closed, i.ethe angle between the last and first station is measured.

The final reading of their leadin8 venire should be the same as its initial reading. lf itdoes not coincideto allthe measured angles.

The following is the method of reiteration;

(i)The instrument is set on o and the initial adjustmenis are more accurately.

(ii)The venire is set to z;ro. The telescope is directed to any directed. to any distinct object p, or to theIeft-extreme object and bisected accurately using the lower clamp and lower tangent screw. The v€nirereading is noted

(iii)The upper plate is loosened and'the telescope is turned clockwise and the object B is bisectedaccurately. Both the venires are noted and the average values gives the angle AOB.

(iv)similarly the objects c and D are bisected successively and reading both the venires at everybisection.

(vlFinally the horizon is closed by sighting the reference object (p)or the tirst point A.

(vi)lt should be noted that the lower clamp and tangent screw remain undisturbed during the revolutionof telescope.

(viii)The face is changed, i.e,, the telescope is trained such that it is upside down and is swing through180'.The circle should be on the left side.

(ix)The vernier A is set to 60'or 90..

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yer././'es 2/'e /edd al every b./3ect/bn.

(xi)other procedures same done for face-left observation.

(xii)The mean of the two results is taken as the exact value.

8. The following bearings were observed with a compass; where do you suspect local attraction? Find

the correct bearings? {MayIune 2006)

Solution;

Difference between FB and BB of 48=254"0'-74' = 180'0'

Difference between FB and BB of BC=271'0'-91"0' = 180'0'

Difference between FB and BB of CD=433"0'-L66"O' = 177"0'

Difference between FB and BB of DE= 177"0'-0"0' = 777"0'

Difference between FB and BB of EA=189'0'-9"0' = 180'0'

Station A,B and C are not affect by local attraction,

F.B. of CD

B.B of CD

=166"0'

= 166'0'+180"0' = 346"00'

Observed reading = 343"00'I

Correct BB of CD = 343'0b'+3'00' = 346"00'

Correction to FB of DE = +3"00'

Corrected FB of DE = 177'00'+3'00' = 180"0'

BB of DE = 0"00'

AB 7 4"OO' BA 254"00',

BC 91"0o', CB 277"OO',

CD 166"00', DC 343"0o',DE t77"00' ED 0'00'EA 189"00', AE 9'00',

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Corrected bearing are

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(x)The horizontal angles are measd;ed in the same manner.This time the telescope is turned in the anti-

clockwise direction.

Thus operation is done to compensate for ship and errors due to twisting of the instrument .Both the

venires are read at every bisection.

(xi)Other procedures same done for face-left observation.

(xiilThe mean ofthe two results is taken as the exact value.

8, The followlng bearlngs were obsewed with a compassl where do you suspect local attraction? Find

the correct bearlngs? (Mai/une 2006)

AB 74"4 BA 254"O',

BC 91'0' CB 271"O'

CD 166'O DC 343'o',

DE t77"d ED 0'0'EA 189'0' AE 9'0'

S@;Difference between FB and BB of

Difference between FB and BB of

Difference between FB and BB of

Difference between FB and BB of

Difference between FB and BB of

station A,B and C are not affect by local attraction.

AB=254o0'-74' :180'0'

BC-271'0'-91'0' =180'0'

CD=433"0' -t65'A = t77"O'

oE=r77"O'-O"0' =777"0'

EA=189"0 -9'0' = 180'0'

F.B. of CD

B.B of CD

. =166"0'

= 165'0'+180'0' = 346'00'

Observed reading = 343"00'I

Correct BB ofCD = 343'0b'+3'00' = 346"00'

Correction to FB of DE = +3'0d

corrected FB of DE = 177'00',+3"00', = 180'0',

BB of DE = 0'00'

.AB7 4"O0', BA 2S4"OO',

BC 91'00' CB 27r"Oo',

CD 166'OO DC 343'00',DE L77"00', ED 0'00'EA 189"00', AE 9'00'

E

Corrected bearing are

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1,

1. Explairi the procedure for solving three point problem by the Lehman meth od? AOUfreL r eol{

(i) set the table at p and orient the tabre approximately so that ab is parallel to a clamp the table(ii) Keep the alidade pivoted about a and sight a draw the ray similarly draw rays from b&c towards b

and c respectively if the orientation is correct the three rays will meet at one point if not they will meet

in three points forming one small triangle of error

(llt) The triangle of error so formed will give the idea for the further orientation the orientation will be

correct only when the triangle of error is reduced to one point to do this choose the point p as shown

the approximate choice of the posltion may be done withrthe help of lemons rules described later

(lv) Keep the allotted alonB pa and retaliate the tablelto cite a champ the table this will give next

approximate orientation

(v) Keep the ray similarly keep the alidade at c and sight c draw the ray these rays will again meet in one

triangle the size of which will be smal[er than the previous triangle of error if p has been chosen

judiciously keeping in the view the lemons rules

(vl) Thus by successive trial and error the triangle of error can be reduced to a point the final and correct

position of the table will lie such that the rays Aa ,Bb, cc, meet in one single point giving the point p the

whole problem tlius involves a fair knowledge of linens rules for the approximate fixation of p so that

the triangle of error may be reduced to a minimum. The lines joining A, B, c from a triangle known as

great triangle similarly the circle passing through A, B, C or a,b,c is known as great circle

2.Lehmanns rules :

(l) lf the station p is outside the greater triangle ABC the triangle of error will also fall outside the great

triangle and point p should be chosen outside the triangle of error slmilarly if the station p is inside the

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ANNA UN]VERSITY PREVIOUS YEAR ESTIONS - 16 MARKS

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(lv) q;) if the posrtion ofA,B,c and p are such that p Ines on or near the side ofAC of a great trianSre thepoint p must be so chosen 4 habit is in between the two para*er rays drawn a ou a .L ,o ,n" n * *each ofthree daysto satisfy rule 3 l

b') if the point p as in 4a ries on or near proronged rine AC, the point p must be chosen outsrde theparallel rays and to the rlght of each the three rays to satist, both rules 2&3c') if4 4 c happens to be in one straight line the Breat trrantre will be one stralght rine only and.thegreat circre wifl be havin8 ABc as its arc th€ radius of which is inffnite in such .rser-tt

" ,o,na , ,rr, o.so chosen that the rays draw to the middre point is b/w the point p and the pornt we got by th€

, , ,,.,,. 'n*o"@

of the rays to the extreme point

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d.) if the position A,B,C and p are such that plies on the great circle the point p cannot be determined by

three point problem because three rays will intersect in one point even when the table is not all

oriented

2, Ust out the dlfferent types and sources of error in plane table surveyi ng, (me7 / fit'O ' 2'o t'!)

lnstrumental error: Error due to bad quality of the instrument.This includes all errors described for the

theodolite iftelescopic alidade is used I

Errorc of Plottlng

Errors due to manipulatlon & slghtlng

. Non-horizontality of board

. Defective sighting

. Defectiveorientation

. Movement on board between sights

. Defective or inaccurate centering

NON - HORIZONTATIW OF BOARD:

The effect of the non - horizontality of the board is more severe when the difference in elevation b/w

the points sighted is more

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DEFECTIVE SIGHTING: I

The accuracy of the prane tabre mapping depends rargery upon the precision with which points aresiShted'The plain alidade with open sight is much inferior to the telescopic alidade in the definition ofline of sight

DEFECTIVE ORIENTATION:

orientation done with compass is unreliable, as there is every possibility of local attraction. Erroneousorientation contribute towards distortion of survey. This orientation shourd be checked at as manystations as possible by sighting distant prominent objects already plotted.

MOVEMENT ON BOARD BETWEEN SIGHTS:

Due to carelessness of the observer, the tabre may be disturbed between any two sights resurting in thedistribution of the orientation. To reduce the possibility of such movement, the clamp should be firmlyapplied. rt is always advisabre to check the orientation a{the end of observation from a station.

INACCURATE CENTERING:

It is very essential to have a proper conception of extent of error introduced by inaccuratecentering, as it avoid unnecessary waste of time in setting up the tabre by repeated triars..

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Compare two point & Three point problem in prlane tabling ? I $ry [5 u,u- - po

Two point problem Three point problem

Location of position on the plan, of ttre stationoccupied by plane table by means of observationsto two well defined points whose positions havebeen previously plotted on plan.

Location of the position on the plan, of the stJtionoccupied by means of observations to three well-defined points whose positions have beenpreviously plotted on the plan.

Two point problem also gives both an orie-nfotionas well as fixing.

ln tflree point problem orientation and resectionare accomplished in same operation.

9"\

4. Explaln the use of plane tabllngln detail surveying? f^*A I S"t* - *"{The plan is drawn by the out -ddor surveyor himself while the country is before his eyes and therefore

there is no possibility of omitting the necessary measurements

o The surveyor can compare ptotted lrlork with the actual features of the area

since the area is in view, contour and irregular objects can be represented accurately

Direct measurements may be almost entirely dispensed with, as the linear and angular

dimensions are both to be obtained'by graphical means

Notes of measurements are seldom required and the possibility of mistakes in the booking is

eliminated

It is particularly useful in'magnetic areas where compass may not be used

It is simple and hence cheaper than the theodolite or any other type of survey

It is most suitable for small scale maps

No great skill is required to produce a satisfactory map and the work may be entrusted to a

subordinate.

S.Explainaboutsurveyorscompass Lr*t ll*u - WtSln surveyo/s compass, the Braduated ring ls directly attached to the box and not with a needle. The

edge bar needle freely floats over the pivot. Tthe object vane is similar to that of prismatic compass. The

eye vane conslsts of a slmple metal vane with fine slit. Since no prism is provided, the object is to be

sighted first with the object and eye vanes and the reading is then taken agalnst the north end of needle

by looking vertically through the top glass.

When the line of sight is in magnetic meridian, the north and south ends of the needle will be over

0' N & 0' S graduations of graduated card. The card is graduated in quadrantsystem havingODeg.atN

and S ends and 90 De8. at East and West ends. Let us take the case of a line AB which is in the NE

quadrant. ln order to sight the point B, the box will have to be rotated about a vertical axis. tn doing so

the pointer of the needle remains fixed in position while 0 Deg. N graduation of card moves in a

clockwise direction.

Temporary Adjustments: (i) Centering, (ii) Levelling, (iii) Focussing the prism

Permanent Adjustments: (i) Adjustments of levels, (ii) Adjustments of sight vanes, (iii) Adjustment ofneedle, (iv) Adjustment of pivot point

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6. TheJbflowlng are the bearlng taien on a compass traverce (uo't' 9Ac - ?o1t)

LINE FB

AB 5370 30',E

BB

N 37 030',WI'

BC 543.15 1^/', N44015',E

cD nl73.O(yw S72015'E

-DE. ' ' 12045E S13015W

EA N60c00,E s59000,w

Compute the interior angles by applying correction for errors assume that there is no local attraction

<A = 37. 30 + 59 .3d=95. 3d

<B = 180. - (37o 30/ {43. 15'} =' 99 olY

<c = 44 .15' + 7300 ,= 117 o15

<D = 1800 -(12.45' + 72c 15') = 95c

<E = 18Oo + 13015' - 600 = 133015'

<A+<BP<C+<D+< E = 541 o15'

t2r*10}g0 = 54O

Efror = 541 15 - 500 = H 15 (positive)

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