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VIMAL JYOTHI ENGINEERING
COLLEGE Chemperi, Kannur 0460-2213399, 2212240
Perfection is the
tradition...
SURVEY PRACTICAL-1
INSTRUCTION MANUAL
Prepared by
Biju Mathew
Head of the Department DEPARTMENT OF CIVIL ENGINEERING
INSTRUCTIONS TO BE FOLLOWED BY STUDENTS 1. Dress code- Green coat over uniform and Black Shoe. Boys should insert
their shirt and girls should put up their hair.
2. Bring with them their own lab manual, calculator and other accessories for
doing the experiment.
3. Study the manual thoroughly before entering the lab.
4. The squad leader should submit the list of instruments required with the
counter signature of the staff in charge of the class. They should check the
instruments before proceeding the practical class and report the damages if
any to the concerned laboratory staff. The squad will be responsible for any
loss or damage caused to any instrument after issue.
5. Handle the instruments with maximum care and if any defect or damage
happens to the instruments, the matter should be immediately reported to the
staff member in charge and they have to obey the directions of the staff
member.
6. Return the instruments 15 minutes before the expiry of the period prescribed
for the practical class.
7. The observations should be entered in the lab manual in ink in the class itself;
where corrections are made, the new reading is to be entered only under the
initials of the staff member.
8. Once the experiment is over, the observations are to be got counter signed by
the staff member. If any calculation has to be done, it should be finished
during the practical class itself, unless the staff member permits to complete it
at a later stage.
9. Gets the lab manual signed by the staff member before leaving from the
practical class. No student is allowed to write the record before lab manual
signed by the staff member.
10. The record should be submitted in next practical class or according to the
directions of the staff member in charge of the class.
11. Lab should be kept clean.
Attendance Policy: Students are required to attend all laboratory sessions. A
student who misses a lab will receive a zero marks for the lab and any associated
reports. No makeup labs will be given. The lowest pre-lab report score and post-lab
MARK DISTRIBUTION
Awarding internal marks: Total marks: 50
Lab Practical’s and Record = 30, Test = 20
University: Out of total 100 marks 70 marks are allotted for writing the
procedure/formulae/sample calculation details, conduct of experiment, tabulation, plotting of
required graphs, results, inference etc., as per the requirement of the lab experiments, 20
marks for the viva-voce and 10 marks for the lab record.
report score will be dropped in computing final averages.
LIST OF EXPERIMENTS
Sl
No
Experiments Page
No
1 STUDY OF CHAIN SURVEY INSTRUMENTS
2 CHAIN SURVEY TRAVERSING AND PLOTTING OF DETAILS
3. STUDY OF PRISMATIC COMPASS
4. COMPASS TRAVERSING AND PLOTTING
5. STUDY OF PLANE TABLE
6. PLANE TABLE TRAVERSING
7. PLANE TABLE SURVEY METHOD OF RADIATION
8. PLANE TABLE SURVEY METHOD OF INTERSECTION
9. PLANE TABLE SURVEY SOLVING THREE POINT PROBLEM
10. STUDY OF LEVELING INSTRUMENTS
11. REDUCTION OF LEVELS BY H I METHOD
12. REDUCTION OF LEVELS BY RISE AND FALL METHOD
13. LONGITUDINAL AND CROSS SECTIONING OF THE GIVEN ROAD
14. LEVELLING CONTOUR SURVEYING
15. STUDY OF TRANSIT THEODOLITE
16. MEASUREMENTS O F HORIZONTAL ANGLES BY THE METHOD OF REPETITION.
EXPERIMENT NO- 1 STUDY OF CHAIN SURVEY INSTRUMENTS
AIM : study of chain Survey instruments EQUIPMENT- : Chain, Arrows, Tapes, Ranging Rods, Offset Rods, Cross staff or optical square, Plumb bob, wooden mallet, pegs. THEORY : By the various methods of determining distance the most accurate and common method is the method of measuring distance with a chain or tape is called Chaining. For work of ordinary precision a chain is used. But where great accuracy is Required a steel tape is invariably used. The term chaining was originally applied to measure Distance with a chain. The term chaining is used to denote measuring distance with either chain or tape, In the process of chaining, The survey party consists of a leader (the surveyor at the forward end of the chain) a follower (the surveyor at the rare end of the chain and an assistant to establish intermediate points) . The accuracy to which measurement can be made with chain and tape varies with the methods used and precautions exercised. The precision of chaining. For ordinary work, ranges from 1/1000 to 1/30,000 and precise measurement such as Baseline may be of the order of 1000000. The Chain
The chain is composed of 100 or150 pieces of galvanized mild steel were 4mm in diameter called links. The end of each link is bent into a loop and connected together by means of three oval rings which afford flexibility To the chain and make it less liable to become linked. The ends of chain are provided with brass handles for dragging the chain on the ground, each with a swivel Joints so that the chain can be turned round without twisting. The length of the A link is the distance between the centres of the two consecutive middle rings.The end links include the handles metallic rings indicators of distinctive points of the Chain to facilitate quick reading of fractions of chain in surveying measurements.
RANGING RODS: The ranging rods are used for marking the positions of Stations conspicuously and for ranging the lines. Io order to make these visible at a distance, they are painted alternately black and white, or red and white or red White and black successively.The adjustment of the chain should as far as possible be affected symmetrically on either side of the middle so as that the position of central tag remains unaltered. In measuring the length of survey line also called as chain line. It is necessary that the chain should be laid out on the ground in a straight line between the end stations
. Cross-Staff : is the simplest instrument used for setting out perpendicular i.e taking offsets from a chain line. it is easier and quicker method ,but not very accurate .if great accuracy is desired ,the work should be carried out by the theodolite. Open cross staff:- The simplest Type consists two parts 1) the head 2) the leg .the head ismade of wooden block octagonal or round in shape about 15cm side or diameter an 4cm deep . On it are scribed two lines at right angles to another .At the end of thesetwo lines are fixed two points of metallic strip having slits made in them. These slits two lines of sight which are at right angles to one another .The head is fixed on a wooden staff or pole about 3cm in diameter and 1.2 to 1.5m length .The pole is provided conical metal shoe so that it can be driven into the ground.
Procedure for using cross staff: – 1) To find the foot of the perpendicular from the object the cross staff is held
approximately in position and one pair of slits is directed in the direction of the ranging rod fixed at the forward and the chain line . The observer then looks through the other pair of slits and sees whether the particular object is bisected or not. if not the crossstaff is moved to and from till the necessary bisection is obtained. Before noting down the chainage of the foot of the perpendicular care must be taken to see that one pairof slit is the direction of chain or not. While shifting the position of the cross-staff it mayget twisted and hence precaution is necessary. 2) To set a perpendicular to the chain line at a given point one pair of slits is oriented inthe direction of chain line by looking at the ranging rod fixed at the forward and bylooking through the other pair of slits ranging rod is fixed in the direction of the line ofsight provided by this pair.
Experiment No. 2-A
CHAIN SURVEY-AREA OF PLOT
AIM:- To determine the area of the given plot. INSTRUMENTS:- Chain, ranging rods, pegs, cross-staffs, arrows, offset rod. PRINCIPLE:-
Measurement by a chain and cross-staff is based upon two formulas. 1. Area of a right-angled triangle is equal to the base multiplied by half the perpendicular Area = bh/2 2. Area of the trapezium is equal to the perpendicular multiplied by half the sum of the bases. Area = h (b1 + b2)/2 3.Area of a triangle is equal ,Area = [Sx (S-A)x(S-B) X( S-C)]1/2
Therefore to calculate the area of every piece of ground, it is only necessary to divide the area into right angled triangles and trapezoids. PROCEDURE:- 1. Before starting survey work, the area to be surveyed to was thoroughly examined to note the various boundaries and positions of area. 2. A base line AE was selected and that is the longest distance. The perpendicular distance offset from the base line was noted by using offset rod and cross-staff by the following procedure.
a) The cross-staff was so positioned that by looking through one of the slits, the ranging rod at the starting point A of the base line AE was visible.
b) Then looking through the other slit, ranging rod placed at B was observed [steps ‘a’ and ‘b’ were repeated until both the ranging rods A and B was visible simultaneously through the slits of cross-staff].
c) The perpendicular distance to ranging rod and the chainage along the base line were noted.
d) Similarly the perpendicular offset C, D, F, G and H were determined.
3. The plan was drawn to a suitable scale and the area was determined. RESULT:- The area of the plot was determined by chain survey. Area of the plot =
Experiment No. 2-B
CHAIN SURVEY-AREA OF A BUILDNG AIM:-
To plot the plan of an auditorium. INSTRUMENTS USED:-
Ranging rods, cross-staff, 30m chain, offset rod and pegs. PRINCIPLE:-
Area of the building is the sum of the area of a rectangle and triangles formed in the building.
Area of rectangle can be found using the formula A = L x B Area of rectangle can be found using the formula A = 1/2 x L x B
Where, ’L’ is the length of the rectangle and ‘B’ is the breadth . PROCEDURE:- 1. A base line AB was taken, which is approximately parallel to the building.
2. The station point A was fixed with a ranging rod on the base line, which was at
considerable distance apart from the corner P of the building but not greater than 3m
due to the fact that offset distance should not exceed 3m.
3. Since the distance between the station point A and B was greater than 30, an
intermediate point was locked between A and B by ranging. The distance AB was
measured using the chain. Similarly the base line BC, CD is selected was selected
and distances were measured.
4. The cross-staff was fixed along the base line AB in such way that two ranging rods
fixed at A and corner of the building are visible simultaneously through the cross-
staff. The point was transferred to the ground [say point C1].
5. The chainage to C1 was measured.
6. Offset length, the distance between the corner point P and C1 was measured
using offset rod. Check measurement was also obtained which is the distance AP.
7. Similarly the line BC,CD,DA were measured and recorded all details in the field
book.
8. The building was plotted to a suitable scale.
RESULT:- Area of the building = Actual area =
Percentage error Experiment No. 3
STUDY OF PRISMATIC COMPASS
INTRODUCTION : Prismatic compass is very valuable instrument. It is usually used
for rough survey for measuring bearing and survey lines.
INSTRUMENTS USED: Prismatic compass, ranging rod, chain, tape, peg, Tripod
stand, small pieces of stones.
PRISMATIC COMPASS:
The important parts of compass are:-
1) A box with graduated circle.
2) A magnetic needle
3) A line of sight
When the line of sight is pointed to point, the magnetic needle of compass points
towards north (Magnetic meridian). The angle which this line of sight makes with
the magnetic meridian is read on graduated circle. It is known as magnetic bearing of
the line. The least count of prismatic compass is 30 min.
Prismatic Compass: It consists of circular box of 10cm-12 cm dia. of non magnetic
material. Pivot is fixed at the centre of box and is made up of hard steel with a Sharp
pivot. Graduated aluminium is attached to the needle. It is graduated in clockwise
direction from 00 to 3600.the figures are written in inverted. Zero is written at south
end and 180 at north end and 270 at the east. Diametrically opposite are fixed to the
box. The sighting vane consists of a hinged metal frame in the centre of which is
stretched a vertical Horse hair fine silk thread of which is stretched a vertical hair. It
presses against a lifting pin which lifts the needle of the pivot and holds it against the
glass lid. Thus preventing the wear of the pivot point to damp the oscillations of the
needle when about to take reading and to bring to rest quickly, a light spring is
brought lifted inside the box. The face of the prism can be folded out the edge of the
box when North end is used Sometime the sighting vanes is provided with a hinge
mirror Which can be placed upward or downwards on the frame and can be also
Slided along it is required. The mirror can be made inclined at any angle so that
Objects which are too high or too low can be sighted directly by reflecting.
BEARING OF LINES: A bearing of a line is a horizontal angle made by the survey
line with some reference direction or meridian. Meridian may be
1) A true meridian
2) A magnetic meridian
3) An arbitrary or assumed meridian
True meridian: The true geographical meridian passing through a point is a line of
intersection of earth’s surface by a plane containing north south pole and given point.
They are not parallel to each other at different places.
Magnetic meridian:-the direction indicates by a free suspended and a properly
balanced magnetic needle Free from all other attractive forces. The direction of
magnetic meridian can be established with the help of Magnetic compass.
Arbitrary meridian: Any direction is assumed to be the Reference meridian to
Carry out small survey.
Whole Circle Bearing: In whole circle bearing system, the bearing of a line is
always measured clockwise from the north point of the reference meridian towards
the line right round the circle. The angle thus measured between the reference
meridian and the line is called Whole circle bearing of the line. Angles measured will
have value between 0 to 360 degrees.
Fore bearing and Back bearing:
The bearing of the line in the direction of propagation of surveying is called fore
bearing and which in opposite direction is called back bearing.
TEMPORARY ADJUSTMENTS OF A PRISMATIC COMPASS
The compass may be held in hand but for better results it should be fitted at
the top of tripod having ball and socket arrangement. The adjustment of a compass
is done in the following three steps.
1) Centring: - The compass fitted over the tripod is lifted bodily and placed
approximately on the station peg by spreading the leg of a tripod equally. The centre
of the compass is checked by dropping a small piece of stone from the centre of the
bottom of the compass so that it falls on the top of the station peg. A plumb bob may
be used to judge the centring either by attaching it with a hook providing at the
bottom or otherwise by holding it by hand.
2) Levelling:-After the compass is centred, it is levelled by means of ball and socket
arrangement so that the graduated circle may swing freely. It can be checked
roughly by placing a round pencil on the top of the compass, when the pencil does
not move, that is roughly the horizontal position.
3) Focusing the prism: - The prism attached is moved up and down so that
graduation on the graduated circle should become sharp and clear.
COMPASS TRAVERSING
In traversing, the compass is set up and the successive back and fore bearing at
each of the points on the line are observed. The field work has reconnaissance,
marking and referring of station, picking up of detail, etc.
The selected station should be such that:
1. They are visible from each other.
2. Chaining between them is easy.
3. The line joining them is the boundary and the object to be located is as near as
possible. If there are errors in the bearings, it should be corrected before they are
used in plotting. The traverse may be done in clockwise or anti-clockwise direction.
RESULT
The study of instruments for compass survey was done.
Experiment No. 4
COMPASS TRAVERSING AND PLOTTING AIM: - To plot the given traverse. INSTRUMENTS : - Chain, tape, ranging rods, offset rod, pegs, arrows, and mallet. PROCEDURE:
1) Four ranging rods are fixed at different points i.e. A, B, C, D, E etc. such that it should be mutually visible and may be measured easily.
2) Measure the distance between them. 3) At point A the prismatic compass is set on the tripod Stand, centring and levelling is
then properly done. 4) The ranging rod at B is ranged through sighting through the slit above the prism,
the compass was turned so that the cross hair of the sight vane coincides with the ranging rod at B.
5) The corresponding compass reading was noted by looking through the prism. This gave the bearing of the line and reading on prismatic compass is noted down.
6) It is fore bearing of line AB. Then the prismatic compass is fixed at B and ranging rod at C. and A is sighted. And reading is taken as forbearing of BC and back bearing of AB.
7) Repeat the same procedure at the stations C, D etc. 8) Calculated and corrected fore bearing and back bearing of each line after applying
correction for local attraction. 9) After noting all the bearings, Included angles were calculated from the observed
fore and back bearing and checked the sum of all angles by using the formulae, (2n-4) x 900
10) Plotted the points A, B, C, D and E using the corrected fore bearing and back bearing.
11) Calculated the area of the traverse ABCDE by calculating the area of triangles by using the formulae, S(S-a)(S-b)(S-c) , where S = a+b+c / 2
Observation Table
Sr. no
Line Observed bearing
Local attraction
error Correction Corrected bearing
Included angle
Error = observed bearing –corrected bearing, Check = (2n-4)x900 RESULT: - 1. The bearing of lines of traverse are Observed, the correction due to local attraction at affected station is done and corrected bearings are written in tabular form. 2. Given traverse is plotted and the Area of the traverse ABCDE = m2
SAMPLE CALCULATION: OBSERVATIONS AND CALCULATIONS
LINE F.B. B.B. CORRECTION CORRECTED LENGTH
IN m F.B. B.B.
AB 167O 30’ 342
O 30’ - 1
O 30’ 166
O 00’ 346
O 00’ 10.15
BC 216O 30’ 40
O 00’ - 3
O 30’ 220
O 00’ 40
O 00’ 13.15
CD 313O 30’ 133
O 30’ 0
O 00’ 313
O 30’ 133
O 30’ 13.80
DE 16O 00’ 197
O 30’ 0
O 00’ 16
O 00’ 196
O 00’ 12.32
EA 96O 00’ 276
O 00’ - 1
O 30’ 94
O 30’ 274
O 30’ 13.10
Included Angle
ABC = 346O 00’ - 220
O 00’ = 126
o 00’
BCD = 360O 00’ - (313
o 30’ - 40
o 00’) = 86
o 30’
CDE = 133O 30’ - 16
O 00’ = 117
o 30’
DEA = 196O 00’ - 94
O 00’ = 101
o 30’
EAB = 274O 30’ - 166
O 00’ = 108
o 30’
Total = 540o 00’
=========
Check :- (2n-4) x 90o
= 540o 00’
(2 x 5 – 4) x 90 o
= 540o 00’
From I le
AC = p2+q
2-2pqCos(10.15)
2+(13.15)
2-2x10.15x13.15xCos126
o = 20.81 m
Area of le = S(S-a)(S-b)(S-c) , where S = a+b+c
2
S = 10.15+13.15+20.81 = 22.06
2
Area = 22.06(22.06-10.15)(22.06-13.15)(22.06-20.81) =54.09m2
From III le
AD = p2+q
2-2pqCos=(13.10)
2+(12.32)
2-2x13.10x12.32xCos101
o 30’ = 19.69 m
S = 13.10+12.32+19.69 = 22.56
2
Area = 22.56(22.56-13.10)(22.56-12.32)(22.56-19.69) = 79.20 m2
From II le
S = 20.81+13.80+19.69 = 27.15
2
Area = 27.15(27.15-20.81)(27.15-13.80)(27.15-19.69) = 130.93 m2
Area of the traverse ABCDE = 54.09 + 79.20 +130.93 = 264.22 m2
Experiment No. 5
STUDY OF PLANE TABLE
AIM: to study instruments used for plane table surveying
APPARATUS: 1) The Plane table with tripod,2) Alidade,3) Trough compass 4) Sprit
level ,5) Plumbing fork or U-frame,6)Plumb bob,7) Tape ,chain, pegs, ranging rods,
wooden mallet etc.
THEORY:
Plane table surveying:
The system of surveying in which field observation and plotting work i.e. both
are done simultaneously is called plane table surveying.
The plane Table:
The drawing board made of well seasoned wood such as teak or pine which is used
for the purpose of plotting is called plane table. It is available in sizes
500x400x15mm, 600x5000x15mm and 750x600x20mm.The top surface of board is
perfectly plane and to the underneath it is fitted with a levelling head or ball and
socket arrangement. The table is mounted on a tripod by means of a central screw
with a wing nut or in such a manner so that the board can be revolved, levelled and
clamped in any position.
Alidade:
The tool or instrument which consists of metal (usually of brass) or wooden (well
seasoned) rule 40cm to 60cm long, 3cm to5cm wide and fitted with two vanes at the
ends is called an alidade. The bevelled graduated edge is known as the fiducial
edge. Such an alidade is known as plain alidade.
Trough Compass:
The compass which is used to mark the direction of the magnetic meridian on the
plane table is called trough compass. It consist of a long narrow rectangular non
magnetic metallic box 8cm to 15cm long, 3cm to 5cm wide and 2cm to 3cm high on
the covered with a glass cover. It the centre of the box is provided a magnetic needle
with a agate stone mounted on the sharp steel pivot. At the end the through
compass graduated scales are with zero degree at the centre and up to 5° on either
side of the zero line. A counter weight is also used for North end of the needle to
represent north and is also used for balancing the dip of the needle.
Sprit Level: A small sprit level circular or rectangular is required for seeing if the
table is properly level. The level must have flat base so that it can be placed on the
table.
Plumbing fork or U-frame: The plumbing fork to which is attached a plumb bob,
used for cantering the plane table over the station occupied by the plane table. It is
also meant for transforming the ground point on to sheet so that both the points
should be in the same vertical line
It consists of two light metal arms as shown in fig. approximately of equal
lengths. A hook for suspending a plumb bob is provided at the lower arm
immediately below the end point of the upper arm. The upper arm is placed on the
plane table while the lower arm with a plumb bob is moved below the table for
centring over the ground station mark, thus in the exact position the pointed end of
the upper arm will give the corresponding position on the paper.
Result: The plane table and accessories were studied.
Experiment No. 7
PLANE TABLE TRAVERSING
AIM: - To plot the details of the given area.
INSTRUMENTS USED: - Plane table and accessories
PROCEDURE:-
1. Set up and level the instrument at A. Using plumb fork transfer A on the
sheet. Draw the north direction using trough compass.
2. With the alidade about 'a' sight various points that can be viewed from A
and plot it to a suitable scale on to the paper by measuring the distance
between A and the points( Necessary details are plotted by radiation
method)
3. If any point is not visible from A, shift the instrument to new station B and
set it. Orient the table accurately by back sighting A. Clamp the table.
4. Pivoting the alidade about 'b' sight the points that can be seen from B and
plot it to a suitable scale on to the paper by measuring the distance between
B and the points
5. New stations are selected and the process is repeated until all the points
are located.
RESULT:-
Experiment No. 8
LOCATING THE INSTRUMENT STATION- RESECTION METHOD (3 POINT
PROBLEM)
AIM: -To locate the instrument station ‘P’ on the plan, by means of observations to
three well defined points A, B & C whose positions have been previously plotted on
the plan and find the distances AV, BV, and CV where V is an inaccessible point
marked on the field in line with AB.
INSTRUMENTS USED: -Plane table and accessories.
PROCEDURE:-
1. Set up and level the instrument at station P.Plot points A, B, C on the paper to
suitable scale as a, b, c.
2. Keep the alidade along ba , and rotate the table until A is bisected ; a being
towards A. Clamp the table.
3. Pivoting the alidade at b, sight C and draw a ray bd through b along the fiducial
edge of alidade.
4. Keep the alidade along ab and rotate the table until B is bisected ; b being
towards B. Clamp the table
5. Pivoting the alidade at a, sight C and draw a ray through a along the fiducial edge
of alidade to intersect the ray previously drawn through b at d. Join cd and
prolong it.
6. Keep the alidade along cd and rotate the table till C is bisected. Clamp the table.
The table is correctly oriented.
7. Pivoting the alidade at b, sight B and draw a ray backward to intersect cd in p.
8. Pivoting the alidade at a, sight A and draw a ray backward, if the work is correct
this ray will pass through p If not repeat the procedure.
9. After locating p, pivot the alidade at p and sight to V and draw a ray towards V.
Mark its intersection V with ab produced. Measure av to scale.
10. Shift the table to ‘D’ and center and level it. Orient the table accurately by
backsighting O and clamp the table
11. Pivoting the alidade about d, sight fourth station V and draw the ray dv”. Rays
ov’ and dv” will intersect the ray at v. Join av , bv and cv. Measure the lengths.
Convert it using the adopted scale and get the distances AV, BV and CV.
RESULT:
1. The instrument station ‘P’ located.
2. The distances AV =
3. The distances BV =
4. The distances CV =
5. Experiment No. 9
LOCATING THE INSTRUMENT STATION- RESECTION METHOD
(2 POINT PROBLEM)
AIM: - To locate the instrument station ‘P’ on the plan, by means of
observations to two well defined points A & B whose positions have been
previously plotted on the plan and find the distances AV and BV where V is an
inaccessible point in the field in line with A & B.
INSTRUMENTS USED: - Plane table and accessories
PROCEDURE:- 1. Plot A and B on suitable scale as a and b.
2. Choose an auxiliary station D near P such that angle PAD and PBD are too
acute nor too obtuse.
3. Set up and level the table at D Orient the table with eye judgment so that
ab is approximately parallel to AB. Clamp the table.
4. Pivoting the alidade on a sight A, draw a ray backwards. Similarly draw the
resector Bb intersecting the previous one in d1.Transfer d1 to the ground.
Mark it with a peg to locate the auxiliary station D.
5. Pivot the alidade at d1 sight P and draw a ray towards it.
6. Mark a point p1 on the ray by estimation to represent the distance DP
7. Shift the table to P, center it so that the point p1 is above p.
8. Orient the table by backsighting on D.
9. Thus orientation at p is same as it was at D.
10. Pivotting the alidade on a, sight A draw a ray backward to intersect the ray
dp1 at p2.
11. Pivoting the alidade at p2 , sight B and draw a ray to intersect with the ray
drawn from D to B in b1.
12. Fix a ranging rod R in line with ab1 and at a great distance. Keeping the
alidade along ab, rotate the table till R is bisected. Clamp the table. Thus
the table is correctly oriented
13. Draw resector Aa and Bb and mark their intersection p. This point p is the
required solution. Pivoting the alidade about p, sight V and draw the ray
pv’. Extend the line ab. It will intersect the ray pv’ at v.
14. Measure the length av and bv multiply with the scale previously used and
get the distance AV and BV.
RESULT:
1. The instrument station ‘P’ located.
2. The distances AV =
3. The distances BV =
Experiment No. 10
STUDY OF LEVELLING INSTRUMENTS
INTRODUCTION Levelling: The art of determining and representing the relative height or
elevation of different object/points on the surface of earth is called levelling. It deals with measurement in vertical plane. By levelling operation, the relative position of two points is known whether the points are near or far off. Similarly, the point at different elevation with respect to a given datum can be established by leveling.
LEVELLING INSTRUMENTS: - The instrument which are directly used for levelling operation are Level, Levelling staff Level: - An instrument which is used for observing staff reading on levelling staff kept over different points after creating a line of sight is called a level. The difference in elevation between the point then can worked out. A level essentially consists of the following parts: 1) Levelling Heads 2) Limb plate 3) Telescope
Telescope consists of two tubes, one slide into the other and fitted with lens and diaphragm having cross hairs. It creates a line of sight by which the reading on the staff is taken
The essential parts of a telescope are 1) Body 2) object glass 3) Eye-piece 4) Diaphragm 5) Ray shade 6) The rack and pinion arrangement 7) Focusing screw 8) Diaphragm screw.
4) Bubble tube 5) Tripod stand DUMPY LEVEL:
The dumpy level is simple, compact and stable instrument. The telescope is rigidly fixed to its supports. Hence it cannot be rotated about its longitudinal axis or cannot be removed from its support. The name dumpy is because of its compact and
stable construction. The axis of telescope is perpendicular to the vertical axis of the level. The level tube is permanently placed so that its axis lies in the same vertical plane of the telescope but it is adjustable by means of captain head not at one end. The ray shade is provided to protect the object glass. A clamp and slow motion screw are provided in modern level to control the movement of spindle, about the vertical axis. The telescope has magnifying power of about thirty diameters. The level tube is graduated to 2mm divisions and it has normally a sensitiveness of 20 seconds of are per graduation. The telescope may be internally focusing or external Focusing type.
ADJUSTMENT OF THE LEVEL The level needs two type of adjustment 1) Temporary adjustment and 2) Permanent adjustment Temporary adjustments of dumpy level
These adjustments are performed at each set-up the level before taking any observation. A) Setting up the level: - this includes 1) Fixing the instrument in the tripod:- the tripod legs are well spread on the ground with tripod head nearly level and at convenient height. Fix up the level on the tripod. 2) Leg adjustment: - Bring all the foot screws of the level in the centre of their run. Fix any two legs firmly into the ground by pressing them with hand and move the third leg to leg to right or left until the main bubble is roughly in the centre. Finally the legs is fixed after cantering approximately both bubbles. This operation will save the time required for levelling. B) Levelling: - Levelling is done with the help of foot screws and bubbles. The purpose of levelling is to make the vertical axis truly vertical.
1) Place the telescope parallel to pair of foot screws.
2) Hold these two foot screw between the thumb and first finger of each hand and turn them uniformly so that the thumbs move either toward each other until the bubble is in centre.
3) Turn the telescope through 90°so that it lies over the third foot screw. 4) Turn this foot screw only until the bubble is centred. 5) Bring the telescope back to its original position without reversing the eye
piece and object glass ends .Again bring the bubble to the centre of its run and repeat these operation until the bubble remains in the centre of its run in both position which are at right angle to each other.
6) Now rotate the instrument through 180°,the bubble should remain in centre 7) Provided the instrument is in adjustment: if not, it needs permanent
adjustment.
c) Focusing the eye piece: - To focus the eye piece, hold a white paper in front of the object glass, and move the eye piece in or out till the cross hairs are distinctly seen.Care should be taken that the eye piece is not wholly taken out ,some times graduation are provided at the eye piece and that one can always remember the particular graduation position to suit his eyes, This will save much time of focussing the eye piece. (d) Focusing the object glass: - Direct the telescope to the levelling staff and on looking through the telescope, turn the focusing screw until the image appears clears and sharp. The image is thus formed inside the plane of cross hairs, Parallax, if any is removed by exact focusing. It may be noted that parallax is completely eliminated when there is no change in staff reading after moving the eye up and down. LEVELLING STAFF: Fig: A levelling staff is a A graduated rod of rectangular cross-section
(a) It is kept vertical at the point whose elevation is known or whose elevation is to be determined.
(b) The levelling staff is sighted through the telescope of the levelling instrument that has been properly set up and adjusted. The reading on the staff corresponding to the cross hair is read.
(c) Made of teakwood, staffs are available in lengths of 3 and 4 metres. (d) Brass cap at the bottom of staff to reduce wear and tear.
(e) Bottom of the staff represents zero reading and the graduations on the staff gives the distances from the bottom of the brass cap. Each metre is divided into 200 divisions. The thickness of each division is 5mm.
(f) Divisions are painted alternatively black and white (g) Top of the numeral indicates the division to which it corresponds.
Classification of levelling staff based on construction (i) Solid staff
Is available in one length of 3m with no joints or hinges in between
No possibility of relative movement between parts and hence readings are accurate
(ii) Folding staff
Available in two pieces of 2m, hinged together so that one piece can be folded over the other when not in use
When taking readings, the two pieces are unfolded to form a staff of 4m.
IS 1779-1961 covers the specifications for 4m levelling staff. It shall be made of well-seasoned timber of width 75mm arid thickness 18mm.
The folding staff is of detachable type with a locking device at the back and hence can be detached and used as a 2m staff when required. It is more accurate than the telescopic staff
(iii) Telescopic staff
The telescopic staff consists of three pieces with a solid upper piece and two hollow lower pieces. The upper piece of 1.25m length can be slide into the middle piece of 1.25m, which in turn can be slide into the lower piece of 1.5m.
The staff can be extended to full length when being used. The three pieces when fully extended are kept in place by flat brass springs.
Holding the staff Utmost care must be taken while holding the staff. The staff man must stand behind the staff with heels together and the heel of
the staff between his/her toes. The staff is to be held between the palms of the hands at the height of his
face. Certain types of level are equipped with a level or plumb bob to make it plumb.
In ordinary work, the staff is waved slowly forward and backward and the lowest reading is taken.
When the point whose reduced level is to be determined is above the plane of sight, the staff is held inverted with the base touching the point (example: the soffit of a roof slab)
Reading the Staff To take readings on the staff, the telescope is directed towards the staff
placed at the point which is either a point of known elevation or a point whose elevation is to be determined.
Focus the objective so that the image of the staff is seen clearly. Now, observe the position of the horizontal cross hair on the staff and take
the readings. The different arrangements of cross hairs are shown In Fig.
Inverted staff reading: When the B.M of staff station is above the line of collimation (or line of sight) the staff is held inverted on the point and reading
is taken .This reading being negative is entered in the level field book with minus sign, or to avoid confusion, ‘Staff inverted’ should be written in the remarks column against the entry of the reading.
RESULT: The instruments used for leveling were studied
Experiment No. 11
REDUCTION OF LEVELS BY H I METHOD
AIM:-
To find the elevation of the given points by Height of Instrument method using a Dumpy
Level and also find their level difference.
INSTRUMENTS USED:-
Dumpy level and Leveling staff.
PROCEDURE:-
1. Set up the dumpy level at a convenient position and carry out all temporary
adjustments
2. Take the reading to the staff kept on a Bench mark (B.M). This is the first reading in
the set up and known as Back Sight (B.S) which is entered in the B.S column of the
field book. The last staff reading in the same set up is known as Fore Sight (F.S). In
between readings from the same set up are known as intermediate sight (I.S).
3. Height of collimation / Height of Instrument (H.I) is obtained by adding the staff
reading observed at a point of known elevation (B.M) to the elevation of that point.
4. Reduced Levels (R.L) of all other stations observed from this instrument station is
obtained by subtracting the corresponding staff reading from the height of instrument
5. When the instrument is shifted, the new height of instrument is calculated by adding
the staff reading observed to a station of known elevation to that station.
Arithmetic Check: To verify the accuracy of the calculation a check is applied. If the
calculation for reducing the level are all correct then BS- FS will be equal to, last R.L-
First R.L by magnitude and sign, which is the arithmetic check.
RESULT: -
1. The elevation of the points
2. The level difference.
OBSERVATION
Staff
station
Back
sight
Intermediate
sight
Fore
sight
Height of
instrument
Reduced
level
remarks
Arithmetic check: -
Calculations:-
Experiment No. 12
REDUCTION OF LEVELS BY RISE AND FALL METHOD
AIM:-
To find the elevation of the given points by rise and fall method using a Dumpy Level
and also find their level difference and Gradient of the line AB.
INSTRUMENTS USED:-
Dumpy level and levelling staff.
PROCEDURE:-
1. Set up the dumpy level at a convenient position and carry out all temporary
adjustments and observe the reading to the staff kept on a Bench mark (B.M).
2. This is the first reading in the set up and known as Back Sight (B.S) which is entered
in the B.S column of the field book.
3. The last staff reading in the same set up is known as Fore Sight (F.S). In between
readings from the same set up are known as intermediate sight (I.S).
4. Calculate the difference of level between consecutive points by comparing the staff
readings on the two points for the same setting of the instrument.
5. The difference between their staff readings a rise or fall according as the staff reading
at the point is smaller or greater than at the preceding point.
6. R.Lof any point= R.L of the preceding point + Rise/Fall
Arithmetic Check: To verify the accuracy of the calculation a check is applied. If the
calculation for reducing the level is correct then BS- FS will be equal to, Rise- Fall
and it will be again equal to the last R.L- First R.L by magnitude and sign, which is the
arithmetic check.
Gradient of the line: To find the gradient of the line, find the level difference between
the points and measure the inclined distance between the points. Calculate the horizontal
distance from these two and then find the slope /gradient of the line
RESULT: -
1. The elevation of the points
2. The level difference.
3. Gradient of the points
OBSERVATION
Staff
station
Back
sight
Intermediate
sight
Fore
sight
Rise Fall Reduced
level
remarks
Arithmetic check: -
Calculations:-
Experiment No. 13
LONGITUDINAL AND CROSS SECTIONING OF THE GIVEN ROAD
AIM:-
To plot the longitudinal and cross sections of the given road
INSTRUMENTS USED:-
Dumpy level and Levelling staff.
PROCEDURE:-
1. Run a chain line along the centerline of the road.
2. Take staff readings at every 10m interval, at critical points where there is a sudden change
of levels at the beginning and end of the curve.
3. For plotting C/S take staff readings at right angles to the centerline at 2m intervals (to the
left and right).
4. Enter the chainages and staff readings in the respective columns of field book.
5. It is necessary to start the work and close it at a Benchmark.
6. Reduce the levels of the stations either by H.I or Rise and fall method.
Plotting the longitudinal section:
Select a suitable scale for plotting the chainages (horizontal scale) say 1:100.Mark the
chainages along a horizontal line. Draw a suitable datum line parallel to the horizontal line
(2.5 cm above it) and mark the datum
R.L. Select a suitable vertical scale for showing the R.Ls of the centerline stations
(1:10).Erect the ordinates at chainages 0,10,20 etc.(ordinate at any station= R.L of the station-
datum R.L).Join the points by straights to get the longitudinal section.
Plotting the cross section:
Plotting of cross section is similar to that of longitudinal sectioning. It is usually plotted in
the same horizontal and vertical scale. It is necessary to plot the c/s at each chainage.
RESULT:
1. The longitudinal and cross sections of the given road was plotted.
STUDY OF TRANSIT THEODOLITE.
Experiment No. 15
14.1 INTRODUCTION
14.2 PARTS OF A THEODOLITE
14.3 DEFINITION
1. Line of collimation
2. Axis of the plate level
3. Axis of the altitude level tube.
4. Face left condition.
5. Face right condition.
6. Plunging the telescope.
7. Swinging the telescope.
8. Changing face.
14.4 TEMPORARY ADJUSTMENTS OF A THEODOLITE
Experiment No. 16
MEASUREMENTS OF HORIZONTAL ANGLES BY THE METHOD OF
REPETITION.
15.1 AIM:-To determine the horizontal distance between accessible points by measuring
the horizontal angle by method of repetition.
15.2 INSTRUMENTS USED:-Theodolite , ranging rods and peg.
15.3 PRINCIPLE:-
To measure the horizontal angle to a finer degree of accuracy than that obtainable with
the least count of the vernier. The same angle is measured several times without setting it
back at zero when sighting at the previous station. Thus the angle reading is mechanically
added several times depending upon the repetitions. The average horizontal angle is
obtained by dividing final reading by the number of repetitions.
15.4 PROCEDURE
P R
O
O
Set up the theodoite over station O and do all the station adjustments. With the help of
upper clamp and tangent screw set 00 00’ 00” on vernier A. Note the reading of vernier B.
Sight to the point P, by loosening the lower clamp. Do the correct bisection by lower
tangent screw. Unclamp the upper clamp and turn the instrument clockwise towards R.
Clamp the upper clamp and bisect R accurately with upper tangent screw. Note the readings
on verniers A and B to get the approximate value of angle POR.Unclamp the lower clamp
and turn the telescope clockwise to sight ‘P’ again. Bisect ‘P’ accurately by lower tangent
screw. Unclamp the upper clamp, turn the telescope in clockwise direction to bisect ‘R’ and
do correct bisection by upper tangent screw. Repeat the process for required no. of times
(n). The average angle with face left will be equal to final reading divided by ‘n’. Change
the face and make ‘n’ repetitions as described above. Find the average angle. The average
horizontal angle is then obtained by taking the average of the two angles obtained
with face left and face right. Measure the distance OP and OR and apply cosine rule to
calculate the distance between the points.
15.5 RESULT