surveying and leveling-2
TRANSCRIPT
DEPARTMENT OF CIVIL ENGINEERING
Surveying-2 Field Book of Group-04
Prepared By: Gulfam akram 2013-CIV-336
0346-7473080
U N I V E R S I T Y O F E N G I N E E R I N G A N D T E C H N O L O G Y L A H O R E ( N A R O W A L C A M P U S )
Job # 1
Title: Study of Topcon Theodolite
Objective: To get knowledge about transit theodolite and study about its
different parts.
Apparatus:
i) Transit Theodolite ii) Tripod iii) Plumb Bob
Related theory:
Definition:
A theodolite is a precise instrument for measuring angles in the horizontal and vertical
planes. A theodolite enables angles to be accurately measured in both the horizontal and
vertical planes. How accurately this can depend partly on the quality of the instrument, and
partly to the competence and experience of the Surveyor.
Basic Types: In 19th century, On the basis of movement of telescope it has been divided into two main types.
1-Transit theodolite 2- Non- transit theodolite In first one telescope can be revolved up to 180° i.e., Transit but in second one
telescope can’t revolve up to 180°. It featured a telescope that could flip over to allow easy back-sighting and doubling of angles for error reduction.
Description of Components: Following are the parts of Theodolite which are discussed as
follows:
1-Telescope: In theodolite, it is used to view our target/object that is actually to measure the
angles which need for complete description of land that is between two station points .It has eye-piece and object glass. On it, screws are present to adjust circle for centering as well as to see the cleared image in object glass by finishing blurredness.
2-LCD & Keyboard:
As theodolite gives digital reading that has been displayed on LCD. Along
with LCD, there has been keyboard having different controls/buttons to attain different modes/target. On keyboard there are six buttons that are used for different purposes. These
are given below i- Power Button ii-Function iii-R/L
iv- V% v- Zero Set vi-Hold
Note:
Face left: The theodolite position in which the vertical circle is on the viewer's left while he looks into
the telescope.
Face right: The theodolite position in which the vertical circle is on the viewer's right while he looks into
the telescope.
Telescope
Sighting
collimator
Lifting handle
Vertical
circle
Optical
plummet
Base plate
Vertical
clamp
Operating
buttons
LCD
screen
Leveling
screws
Vertical
slow motion
srew
3- Vertical Scale (or Vertical Circle): It is known as graduated circle. It is a full 360° circle. It has been kept standard to decide the face of theodolite. If vertical circle is at left side of Surveyor while taking observations then that will be the face either left or right.
4- Vertical clamp / Tangent screw: In order to hold the telescope at a particular vertical angle a
vertical clamp is provided. This is located on one of the standards and its release will allow free transiting of the telescope. When clamped, the telescope can be slowly transited using another fine adjustment screw known as the vertical tangent screw.
5-The Horizontal clamp and Tangent screw: Th horizontal clamp is provided to clamp the horizontal circle. Once the clamp is released
the instrument is free to traverse through 360° around the horizontal circle. When clamped, the instrument can be gradually transited around the circle by use of the horizontal tangent screw.
6-Bubble tube, Leveling screws and circular bubble: All these are the parts of theodolite that is helpful in setting the theodolite. Leveling of instrument is done by leveling screws and
circular bubble must be in center for correct setting of theodolite. Note: circular bubble is also known as pill bubble and bull’s eye.
7-Slow-motion screw: The fine adjustment screw used to translate the theodolite in the horizontal or vertical plane
when the horizontal or vertical clamp is tightened.
Setting of a Theodolite:
1-Tripod Setup: Following steps are involved in setting up a
tripod.
a) Place the tripod over the positioning mark, setting the legs
at a convenient height, and roughly center and level the
tripod head by naked eye
b) Firmly fix the tripod feet in position. If necessary, adjust
the heights of the tripod legs to re-center the tripod.
2- Theodolite Setup (Centering & leveling):
a) Place theodolite on tripod and fix it on tripod.
b) Looking through the optical plummet, focusing
the centering index mark. Slide the theodolite on
tripod until the reference mark is centered in the
optical plummet.
c) Fully tighten the centering screw. Look through
optical plummet we may adjust the theodolite
foot screws for alignment with reference mark.
d) By adjusting the length of two tripod legs at a
time while keeping the other one still, the
circular bubble can be leveled without causing
disturbance to the previously accomplished centering (check the optical plummet to
see this is true).
e) Rotate the theodolite until its plate bubble is parallel to any two foot screws, and then
adjust these screws to center the bubble. Now rotate the theodolite body by 90, and
center the bubble with the third foot screw only.
Repeat this procedure for each 90 revolution of the
instrument until the bubble is centered for all four
positions. Now check the optical plummet: adjustment
of the foot screws has probably disturbed the
centering.
f) Loosen the tripod screw, and slowly translate (do not
rotate) the theodolite around until it is exactly centered
over the survey point, then tighten the screw.
3-Packing Up:
(a) Turn off
theodolite
(c) Align the theodolite as it was before packing
(d) Bring the theodolite foot screws to the center of
their travel
(e) Holding the theodolite handle
with one hand, undo the centering
screw with the other.
(f) Put the theodolite back in the box in its original position and close the clasps.
(g) Being careful not to disturb the positioning mark, lift the tripod
away , collapse it, and put it away.
Precautions:
Set the instrument carefully
Use theodolite carefully
Bisect the target with accuracy
Unclamp before attaining required movement.
COMMENTS:-
The station points are not visible from other stations.
The poles are not placed at the stations to locate only one station.
The center of plumb bob and optical plummet was not same.
Job # 02 Title: Measurement of Base Line by Manual Method Objective: To find out the length of base line with complete accuracy by Applying all
Corrections.
Apparatus:
I. Theodolite
II. Auto level
III. Thermometer
IV. Spring balance
V. Supporting stands
VI. Mallet & Pegs
VII. Steel tape
VIII. Fiber glass tape
IX. Leveling staff
Related Theory:
Base Line:
In triangulation the base line is of prime importance (b/c). It is the only for distance to measured. It should be measured
very accurately since the accuracy of the computed sides of triangulation system depends on it. Length of base line
varies from a fraction of (0.5-10) km and a fraction of a mile to 10 miles.
And selecting site for a base line, the following requirement should be considered:
1. The site should be fairly leveled or uniformly sloping or gauntly undulating.
2. Should be free from obstructions throughout the entire length. 3. Ground should be firmed and smooth. 4. The site should be such that the whole length can be laid out the extremities of the line being visible at ground
level. 5. The site should be such that well shaped triangle can be obtained in connecting the end stations of the base line
to the main triangulation stations.
Theodolite:
A theodolite is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites
are mainly used for surveying applications. A modern theodolite consists of a movable telescope mounted within two
perpendicular axes—the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a target
object, the angle of each of these axes can be measured with great precision, typically to seconds of arc.
Least count: Its L.C. is 5”. But 1” L.C. is also available.
Auto level:
Auto level, leveling instrument, or automatic level is an optical instrument used to establish or check points
in the same horizontal plane. It is used in surveying and building to transfer, measure, or set horizontal levels.
Thermometer:
A thermometer is a device that measures temperature or temperature
gradient using a variety of different principles. A thermometer has two important
Eye piece
Focusing screw
Telescope
Object glass
Leveling screws
Circular bubble
Slow motion
screw
Base plate
elements: the temperature sensor (e.g. the bulb on a mercury thermometer) in which some physical change occurs with
temperature, plus some means of converting this physical change
into a numerical value (e.g. the scale on a mercury thermometer).
Least count: Its L.C. is 1 degree.
Spring Balance:
A spring balance apparatus is simply a spring fixed at one
end with a hook to attach an object at the other. It works by Hooke's
Law, which states that the force needed to extend a spring is
proportional to the distance that spring is extended from its rest position.
Therefore the scale markings on the spring scale are equally spaced.
Before using this instrument we should check its zero error.
It may be of two types:
i. +ve zero error
ii. -ve zero error
+ve error is subtracted and –ve error is added in the measurement taken.
Supporting stands:
Supporting stand/wooden tripod/ trussles are the tripod stand which we have used to divide the line into the
length less than the 30 m tape length and for the line along the actual base line.
Mallet & Pegs:
Mallet & Pegs were used to mark the station point.
Steel tape:
It is 30 m length tape made up of steel. This was used to
measure the length of line in the pull applied condition.
Least count:Its least count is 1 mm.
Fiber glass tape:
It is also a 30 m length tape made up of fiber glass. This was not used in full condition because it would
elongate with full of 5 kg.
Least count:
Its least count is 1 mm.
Leveling staff:
A level staff, also called leveling rod, is a graduated wooden or aluminum rod, the use of which permits the
determination of differences in elevation. It is of 5 m length.
Least count:
Its least count is 0.005 m.
Ranging Rod:
This is 2 m length iron rod divided into many parts which are colored red and
white or white and black. This has one end which can be screwed or the station. This
used where we cannot see the station base.
Procedure:
There are so many method for accurate measurement of base line but the
method we are doing is
Manual method
Select the base line namely as AB.
Set the theodolite at A (initial point) after doing the temporary adjustment
(centering, leveling & focusing) sight the point B (end point of base line).
Divide the base line into lines of length less than the 30 m we which is the length of the tape marks these point
temporary with the pegs.
Set the trussles on these points. These points should be in a line this can be done by the theodolite which is sighting
the point B.
Mark the line of sight on the disk of the trussles. This can be done by a following simple method.
o One person is holding the theodolite at A sighting the point B.
o One person is at the point on trussle. He should move the pensile on the disk of the trussle in
such this is across the line of sight.
o The 1st person will guide the 2nd which way he should move that he can be in the line f sight.
o If he find the line of sight the mark the point on that point.
o In this way find another point on the disk and mark it.
o Join these two points to make the line.
o You can check this put the pensile on the line if this is in the line of sight then the marked line
will be correct.
Find the distance between the point A (base of the point) and the 1st trussle (on the disk).
Apply pull in this length measurement pull should be of 5 kg by the spring balance.
Temperature should also measure during this measurement. Thermometer should be hanged on point (under the
theodolite and trussles).
Set the auto level at a point from where all the point of the line are visible.
After the temporary adjustment (centering, leveling & focusing) find the levels of all points by setting the leveling
staff on each point.
Put all measurements in the table.
Formulas used for correction:
Ct = α(Tm-To) L Temperature Correction
CP = (P - PO) L/AE Pull Correction
CSP = - h2 / 2L Slope Correction
CS = - w2 L3 / 24 P2 Sage Correction
Cmsl = - HL / R Mean Sea Level Correction
Where
L = Measured length of the base (in meter)
α= Coefficient of thermal expansion (0.000011 / 0C)
Tm = Mean Temperature during measurement (0C)
P = pull applied during measurement (kg)
Po = Standardized Pull = 2 kg
A = Area of X-Section of Tape (0.0193 cm3)
E = Modulus of elasticity of tape (21 x 106 Kg/cm2)
H = Difference of elevation between two point (in meter)
W = Weight of tape per unit = o.o10193 Kg / m
H = Mean height of base above sea level = 1180 m
R = Mean radius of earth = 6367 Km
SCHEME USED:
A C F
UMER HALL GROUND
B D E
G
Comments:
In triangulation the base line is of prime importance (b/c). it is the only horizontal distance to measured. It should be
measured very accurately since the accuracy of the computed sides of triangulation system depends on it. Length of
base line varies form a fraction of (0.5-10) km and a fradion of a mile to 10 miles.
MAIN BLOCK
AYESHA HALL
Job # 03 Title: MEASUREMENT OF BEARINGS BY PRISMATIC COMPASS
Objective: To find out the bearings with complete accuracy by Applying all Corrections.
Apparatus:
Prismatic Compass
Tripod Stand
Ranging Rods
Pegs
Mallet
Related Theory:
Introduction to prismatic compass & its parts:
The 'Prismatic Compass' was invented by the maker Charles Schmalcalder and patented in 1812.
Radius of prismatic compass is 40mm.
Parts:
Compass box:
It is a circular metallic box of diameter 8 to 10 cm. A pivot with a sharp point is provided at the
centre of the box.
Magnetic needle:
It is made of broad magnetized iron bar &it is attached to a gruated aluminum ring. The ring is
graduated from 0 ˚to 360˚ clockwise & graduation begins from the south end of needle. Thus
zero is marked at the south, 90˚ at the west, 180˚ degree at the north & 270˚ degree at the east.
Sight vane & prism:
Site vane & reflecting prism are fixed diametrically opposite to the box. Site vanes are hinged
with metal box & consist of wire or hair at the center.
Dark glasses:
Two dark glasses (blue & red) are provided with the prism. Red is use for sighting luminous
object at night & blue for reduction of sunlight.
Brake pin:
It is provided at the base of sight vane & it stops the movement of ring.
Lifting pin:
It is below sight vane & it lifts the magnetic needle out of the pivot point to prevent damage the
pivot head.
Glass cover:
It is provided at the top of box to protect the aluminum ring from the dust.
Some Important Terms:
Bearing: Bearings are angle measured with reference to north.
Fore bearing: Bearing measured in the direction of progress of survey.
Back bearing: Bearing measured in the direction opposite to the progress of survey.
True bearing: A true bearing is measured in relation to the fixed horizontal reference plane of true north,
that is, using the direction toward the geographic North Pole as a reference point.
Magnetic bearing: A magnetic bearing is measured in relation to magnetic north, that is, using the direction
toward the magnetic north pole (in northeastern Canada) as a reference.
Grid bearing: A grid bearing is measured in relation to the fixed horizontal reference plane of grid north,
that is, using the direction northwards along the grid lines of the map projection as a reference point.
Magnetic Declination: It is a horizontal angle between true meridian and magnetic meridian.
There are 2 types of declination.
I-East declination II-West declination
Errors In Compass Observations:
The errors may be classified as
Instrumental errors
Personal errors
Errors due to natural causes
Instrumental Errors:
They are those which rise due to the faulty adjustments of the instruments. They may be due to the following reasons:
The needle not being perfectly straight.
Pivot being bent
Sluggish needle
Blunt pivot point
Improper balancing weight
Plane of sight not being vertical
Line of sight not passing through the center of graduated ring.
Personal Errors:
They may be due to the following reasons:
Inaccurate leveling of the compass box.
Inaccurate centering.
Inaccurate bisection of signals.
Carelessness in reading and recording.
Natural Errors:
They may be due to following reasons:
Variation in declination
Local attraction due to proximity of local attraction forces.
Magnetic changes in the atmosphere due to clouds and storms.
Irregular variations due to magnetic storms etc.
Procedure:
The compass centered over station A of the line AB and is leveled.
Having turned vertically the prism and sighting vane, raise or lower the prism until the graduations on the rings
are clear and look through the prism.
Turn the compass box until the ranging rod at the station B is bisected by hair when looked through the prism.
Turn the compass box above the prism and note the reading at which the hair line produced appears to cut the
images of the graduated ring which gives the bearing of line AB.
Adjustments Of Prismatic Compass:
The following are the adjustments usually necessary in the prismatic compass:
Centering
Leveling
Focusing the prism.
Centering: The center of the compass is placed vertically over the station point by dropping a small piece
of stone below the center of the compass, it falls on the top of the peg marking that station.
Leveling: By means of ball and socket arrangement the Compass is then leveled the graduated ring swings
quite freely. It may be tested by rolling a round pencil on the compass box.
Focusing: The prism attachment is slid up or down focusing till the readings are seen to be sharp and
clear.
Calculation & Observation
Line FB BB Difference Correction Corrected
FB
Corrected
BB
Remarks
AB 351˚00’ 172˚30’ 01˚30’ +00˚45’ 351˚45’ 171˚45’
No
Point
Is
Free
From
Local
attraction
BD 261˚30’ 80˚00’ 01˚30’ -00˚45’ 260˚45’ 80˚45’
DC 168˚30’ 349˚30’ 01˚00’ -00˚30’ 169˚00’ 349˚00’
CA 71˚30’ 250˚30’ 01˚00’ +00˚30’ 71˚00’ 251˚00’
DE 260˚30’ 79˚30’ 01˚00’ -00˚30’ 260˚00’ 80˚00’
EF 165˚45’ 347˚30’ 01˚45’ -00˚52’ 166˚37.5’ 346˚37.5’
FG 335˚00’ 154˚30’ 00˚30’ -00˚15’ 334˚45’ 154˚45’
GE 104˚00’ 285˚00’ 01˚00’ -00˚30’ 104˚30’ 284˚30’
Comments:
Local attraction was present near the station points.
Some station points were free from Local attraction so the difference of forbearing and back bearing at that points is exactly zero.
The Fore bearing is measured in the direction of survey and back bearing is measured opposite to that. For temporary adjustments of prismatic compass we performed following steps.
Fixing the compass with tripod stand.
Centering of the compass by dropping pebble. Levelling by ball and socket arrangement of tripod stand.
Adjusted the prism to see the graduated ring clearly.
Job # 04 Title: Measurement of Horizontal Distance By Tacheometry
Objective: To learn the method of measuring horizontal distance by tacheometry.
Apparatus:
1. Theodolite
2. Leveling staff
Related Theory:
Tacheometry is a branch of surveying in which horizontal and vertical distances are determined by taking
angular observations with an instrument known as tacheometer.
Theodolite:
A theodolite is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites
are mainly used for surveying applications. A modern theodolite consists of a movable telescope mounted within two
perpendicular axes—the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a target
object, the angle of each of these axes can be measured with great precision, typically to seconds of arc.
We have used theodolite of least count 5” as a tacheometer. It is nothing but a transit theodolite fitted with a
stadia diaphragm and an anallatic lens.
Least count: Its L.C. is 5”. But 1” L.C. is also available.
Leveling staff:
A level staff, also called leveling rod, is a graduated wooden or aluminum rod, the use of which permits the
determination of differences in elevation. It is of 5 m length.
Least count:
Its least count is 0.005 m.
Telescope
Sighting collimator
Lifting handle
Vertical circle
Optical
plummet
Base plate
Vertical clamp
Operating buttons
LCD screen
Leveling screws
Vertical slow motion
srew
Characteristics of Tacheometer:
(a) The value of multiplying constant (f/i) should be 100.
(b) The telescope should be powerful, having magnification of 20 to 30 diameters.
(c) The aperture of objective should be of a 35 to 45 mm for there to be a bright image.
(d) The telescope should be fitted with an anallatic lens to make the additive constant(f+d) exactly equal to zero.
(e) The eyepiece should be of greater magnifying power than usual, so that it is possible to obtain a clear staff
reading from a long distance.
Principle of tacheometry:
The principle of tacheometry is based on the property of isosceles triangle, where the ratio of the distance of
the base from the apex and the length of the base is always constant.
In figure shown below, triangles o1a1a2, o1b1b2 and o1c1c2 are all isosceles triangles where D1, D2 and d3 are
the distances of the bases from the apices and S1, S2 and S3 are the lengths of the bases(staff intercept).
So, according to the stated principle,
D1/S1=D2/S2=D3/S3=f/i
The constant f/i is known as the multiplying constant,
Where f= focal length of objective and i= stadia intercept
Methods of Tacheometry:
Tacheometry involves mainly two methods:
1. The stadia method
2. The tangential method
1. The stadia method:
In this method the diaphragm of the tacheometer is provided with two stadia hairs (upper and lower) . The
difference in upper and lower reading gives the staff intercept. To determine the distance between the stations
and the staff, the staff intercept is multiplied by the stadia constant (i.e. multiplying constant , 100) . The stadia
method may, in turn, of two kinds.
(a) The Fixed hair Method
(b) The Moveable Hair Method
2. The tangential method:
In this method, the diaphragm of the tacheometer is not provided with stadia hair. The readings are taken by
single horizontal hair.
We have used FIXED HAIR METHOD.
Fixed Hair Method:
There are three cases in fixed hair method.
Case 1:
When line of sight is horizontal and staff is held vertically.
The equation for distance is given by
D= (f/i) S+ (f+d)
Case 2:
When the line of sight is inclined, but staff is held vertically.
Here, the measured angle may be the angle of elevation or that of depression.
D= (f/i) S cos^2 Ѳ+ (f+d) cosѲ
Case 3:
Line of sight inclined, but staff normal to it.
D= (f/i) cosѲ+(f+d) cosѲ-hcosѲ
Procedure:
First of all, we made the temporary adjustment of the instrument at point A.
We bisected the leveling staff at point B.
After this ,we noted the upper(U) and lower readings(L) of leveling staff at point B, and got staff intercept (S)
by taking their difference.
Staff intercept=S=upper reading –lower reading= U-L
Multiplying staff intercept with multiplying constant, we got distance D between the stations
D= S * 100
We repeated the above procedure for the whole scheme and calculated all the distances.
SCHEME USED:
A C F
UMER HALL GROUND
B D E
G
MAIN BLOCK
AYESHA HALL
No.
of
obs.
Inst.
Station
Staff
station
Hair readings (m)
Staff
Intercept
(S=U-L)
Vertical
angle
(degrees)
Length
of line
(m)
Upper Middle Lower
1 A B 1.60 1.00 0.260 1.34 0 134
2 A D 2.750 2.480 1.75 1.00 0 100
3 B C 1.8 1.11 0.55 1.25 0 125
4 C E 1.650 1.040 0.45 1.20 0 120
5 G E 1.840 1.520 1.395 0.45 0 45
6 E F 1.90 1.350 0.70 1.20 0 120
7 G F 1.95 1.25 0.6 1.35 0 135
8 D C 5.65 4.70 3.9 1.75 0 175
Comments:-
The method we use consists of using a level, theodolite or specially constructed tachometer to make cross hair
intercept readings on a leveling staff. As the angle subtended by the crosshairs is known, the distance can be
calculated.
Job # 05
Title: TO SET OUT REVERSE CURVE
Objective: The object of this survey is to design and set out a reverse curve.
Apparatus:
1. Theodolite
2. Leveling staff
Related Theory:
Reverse Curve:
These are two simple curves with deflections in opposite directions, which are joined by a
Common tangent or relatively shorter distance. OR
A reverse curve consists of two circular arcs of equal or different radii turning in opposite directions with a common
tangent at the junction of the arcs.
Elements of a Reverse Curve:
PQ & RS are the two parallel lines at a distance “Y” apart. The angle of deflection =Ф1=Ф2=Ф. Ф is the angle subtended by the curve.
T1 is the tangent point for 1st curve.T2 is the tangent point for 2nd curve. C is the point of tangency or point of reverse curvature.
Distance salong long chord. T1T2 is the length of the line joining tangent points T1 & T2. X is the perpendicular distance between tangent point T1 & T2. Y is the perpendicular distance between tangent PQ & RS.
Design Parameters of a Reverse Curve:
Long chord for 1st curve T1C= 2Rsin Ф/2
Long chord for 2nd curve T2C= 2Rsin Ф/2
Tangent distance=T1T2= 2Rsin Ф/2+ 2Rsin Ф/2
Total Tangent distance= 4Rsin Ф/2
T1T2= 2√R√Y
As in Triangle
Cos Ф= O1A/O1C
Cos Ф= O1A/R
So R Cos Ф= O1A
From the fig (1)
T1A= O1T1-O1A
T1A=R-R Cos Ф
Y=T1A+T2B
Y=R(1- Cos Ф)+R(1- Cos Ф) :T2B=R(1- Cos Ф)
Y=2R(1- Cos Ф)
From the triangle
Sin Ф= CA/R
R sin Ф=CA
Similarly from the fig (1) for X
X=CA+CB
X=R sin Ф+ R sin Ф :CB=R sin Ф
X=2 R sin Ф
Length of curve Lc= πR Ф/180˚
Chainage of T1= Chainage of C- Length of Curve
Chainage of T2= Chainage of T3+ length of Curve
REVERSE CURVE
Setting out of Reverse Curve:
Apparatus:
Theodolite
Ranging Rods
Pegs
Mallet
Tripod stand
Wooden pegs Tripod stand
Theodolite
The lengths of the reverse curve are normally small. So the curve may be set out by taking offsets from (i) the long
chord or (ii) the chord produced. If the length of the curve becomes large and chaining along it difficult, the curve may
be set out by the deflection-angle method (Rankine’s Method).
All the necessary data for setting out of the curve are calculated in usual manner. The setting out table is prepared.
Tangent points T1 & T2 are marked on the ground. A theodolite is centred over T1 and done all permanent adjustments
related to theodolite. Theodolite is set at 0˚0’0”. Chord lengths are provided so we calculate angle of deflection. Then
length of the curve is calculated. Ranging rods are fixed at given chord length and bisect all the ranging rod with the
help of theodolite so the ranging rods come in a straight line. Tangent length is marked at the half of angle of
deflection.
Then theodolite is again set to zero. And then at initial sub chord the angle of deflection is set & measuring the length
or peg interval by tape set out the angles and fix the peg on the ground so that each peg will be bisteced properly by
theodolite. By marking pegs we reach at the pt. of tangency or pt. of reverse curvature. And then now same procedure
is adopted on the either side of curve. The angle of defection is noted down and pegs are marked so that we reach at
final point T2.
DATA:
Chainage of T1= 2727.27m
R1=90m
R2=70m
FT1=40m
FT2=30m
T1F=2R1 sin Ф1/2
T1F/2R1 = sin Ф1/2
Ф1/2= sinˉ1 (40/2*90)
Ф1/2= 12˚50’
Length of 1st curve=Lc1= πR1Ф/180˚*60
Lc1=40.3m
Chainage of F= Chainage of T1+ Lc1
Chainge of F= 2727.27+40.3
Chainage of F=2767.57m
T2F=2R2 sin (Ф2/2)
Ф2/2= sinˉ1 (T2F/2R2)
Ф2/2=12˚22’25.06”
Length of 2nd curve=Lc1= πR2Ф/180˚*60
Lc2=30.23m
Chainage of T2= Chainage of F+ Lc2
Chainage of T2=2797.8m
2 tables are set out 1st for from T1 to F & then F to T2. Chainage of T1= 2727.27m & that of F= 2767.57m
.Peg interval is taken as 5m.So initial sub chord is calculated by a chossing a suitable round decimal such as 2730m so
initial sub chord is 2.73m & normal chords will be of 5m and that of final sub chord will be 2.57m.
Deflection angle is measured by a formula=1718.9*chord length/(R*60)
Point Chainages (m) Original Deflection Total Corrected
length (m)
angle (DMS)
deflection angle
angle from theodolite 5”
T1 2727.27 - - - -
P1 2730 2.73 0˚52’8.4” 0˚52’8.4” 0˚52’10”
P2 2735 5 1˚35’29.67” 2˚27’38.07” 2˚27’40”
P3 2740 5 1˚35’29.67” 4˚3’7.74” 4˚3’10”
P4 2745 5 1˚35’29.67” 5˚38’37.41” 5˚38’40”
P5 2750 5 1˚35’29.67” 7˚14’7.08” 7˚14’05”
P6 2755 5 1˚35’29.67” 8˚49’36.75” 8˚49’35”
P7 2760 5 1˚35’29.67” 10˚25’6.42” 10˚25’05”
P8 2765 5 1˚35’29.67” 12˚0’36.09” 12˚0’35”
F 2767.57 2.57 0˚49’41.4” 12˚49’41.4” 12˚49’40”
For 2nd Curve when R2=70m
Point Chainages (m) Original length
(m)
Deflection angle
(DMS)
Total deflection
angle
Corrected angle from
theodolite 5”
F 2767.57 - - - -
R1 2770 2.43 0˚59’40.22” 0˚59’40.22” 0˚59’40”
R2 2775 5 2˚2’46.71” 3˚2’26.93” 3˚2’25”
R3 2780 5 2˚2’46.71” 5˚5’13.64” 5˚5’15”
R4 2785 5 2˚2’46.71” 7˚8’0.35” 7˚8’0”
R5 2790 5 2˚2’46.71” 9˚10’47.06” 9˚10’50”
R6 2795 5 2˚2’46.71” 11˚13’33.77” 11˚13’35”
T2 2797.8 2.8 1˚8’45.36” 13˚16’20.48” 13˚16’20”
Job # 06 Title: SETTING OUT OF COMPOSITE CURVE
Objective: To understand and earn the procedure of setting of circular curve
Apparatus:
Theodolite Tripod Stand
Ranging Rods Pegs Mallet
Related Theory:
Introduction to composite curve:
It consists of different types of curve. It is also known as combined curve.
For example: a simple circular curve along with two transition curves on both end is example of
composite curve
Setting Out of Transition Curves:
1. Introduction:
Transition curves, as their name suggests, are designed to allow a smooth transition from a straight section to a (circular) curve and to allow the gradual introduction of super-elevation (also known as “banking” on a racing circuit
and “cant” on a rail track). Setting out of transition curves is done using the same techniques as for circular curves (theodolite and tape or EDM/co-ordinates) and the purpose of these notes is to introduce the calculations required to produce the necessary setting out data.
2. Forces on vehicles moving round curves: A moving object will continue moving in a straight line at constant velocity unless acted upon by a force. If the force
acts in the same direction as the motion, then the object will accelerate or decelerate; if the force acts perpendicular to the line of motion, then the object will change direction. In order to turn a vehicle round a curve, it is therefore
necessary to apply a sideways force – this is done by turning the front wheels. There are two important considerations when designing roads (and railways):
Comfort of occupants: When the vehicle moves round the curve, the occupants feel the sideways force
because their bodies wish to continue moving in a straight line. If this force is too great (curve radius too tight) or it is applied too rapidly (moving from a straight to a sharp circular curve) then the occupants will feel discomfort.
Safety of vehicle: The sideways force is transmitted to the vehicle via the tyres at road surface level. If the force is too great for the grip of the tyres, skidding may occur. If the centre of gravity of the vehicle is high,
then overturning may occur.
The centrifugal force, acting outwards as a vehicle moves round a curve, is expressed as follows:
Figure: Centrifugal force exerted on a vehicle travelling round a curve.
P = W V2 centrifugal force g R
Or P = V2 centrifugal ratio
W g R = V2 with V in km/h
127 R R in m g = 9.807 m/s2
For practical purposes, a “comfort range” is adopted for values of the centrifugal ratio, P/W:
Roads: P/W between 0.21 and 0.25 (typically 0.22) Railways: P/W = 0.125
From this can be derived an expression for the minimum radius required for a particular design speed:
Minimum = V2
Radius (P/W) x 127
Velocity V
Centrifugal
force P
Radius R
Vehicle
Circular curve
R
W
P
This should be regarded as a minimum value; the actual radius adopted (which may be larger) may depend upon other
factors such as the overall alignment of the road.
3. Entry to a curve:
Centrifugal force leads both to passenger discomfort and to slipping/overturning forces on vehicles. On high-speed
roads, and on many modern medium-speed roads, this is counteracted by the application of super-elevation. This is the tilting of the road surface so that the resultant force of the weight of the vehicle and the centrifugal force is close to normal with the road surface. In railway engineering, this is known as “cant”; on a motor racing circuit it would be
called “banking”.
Figure: Super-elevation
The super-elevation angle, , is usually expressed as a gradient (e.g. 1 in 14) and is related to the velocity of the vehicle and the curve radius.
Clearly, this cannot be applied suddenly, but must be introduced gradually. Furthermore, sudden entry from a straight into a circular curve may result in “acceleration shock” to the passengers.
For both of the above reasons, it is preferable to change the radius of curvature gradually from the straight to the
circular curve steadily along a transition curve. Design of transition curves is based upon the change of curvature (the inverse of radius) at a steady rate from the
straight (curvature = 0) to the circular portion of the curve (curvature = 1/R). The rate of change of radial acceleration, q, must also be kept constant whilst the vehicle negotiates the transition curve at constant velocity over time t. This
results in the following relationships: time taken to travel t = L/V
along transition curve
radial acceleration aR = V2/R rate of change of q = aR / t
radial acceleration = (V2/R)/(L/V)
Road surface
W
P
Resultant
force
= V3/RL
i.e. L = V3
46.7 q R with V in km/h and R in m.
An acceptable value of q is found to be 0.33 m/s3. This gives an expression for the minimum length of transition curve
required. The actual length of transition used may also depend upon previous experience. The completed curve now consists of
an entry transition
a central circular portion
an exit transition
Both of the transitions will have identical geometry, but will be of opposite hand.
Shape of the transition To satisfy the criterion that rate of change of curvature must be constant along the transition curve, we must calculate
the shape of the curve as follows.
At a distance l into the transition, measured from the transition tangent point T1, the radius of curvature will be r. At l = 0, i.e. at the transition point, r is infinite, and reduces to the circular curve radius, R, at the circular curve tangent
point T1, where the transition curve joins the circular portion. This situation is shown in the diagram below:
Figure : Shape of the transition curve.
The radius is related to the length l by the equation derived above, i.e.
l = V3
46.7 q r
d
dl
T1
T1
R
l
Entry
tangent
Tangent to
circular
curve
which can be re-written l = K since velocity is
r constant
From figure 3, because angle d is small, we can write:
r d = dl
i.e. d = 1 dl = l dl
r K
This may now be integrated, inserting limits:
= l2 = l2
2 K 2 r l = l2
2 R L
or l = (2 R L )½
This is the equation of the clothoid or Euler spiral. It is regarded as the ideal shape for the transition curve. The
angle consumed by the transition curve, , is
= L (radians)
2 R
= L x 180 (degrees)
2 R
The clothoid is regarded as the “ideal” shape for a transition curve, as it satisfies our criteria for all values of . However, although it appears simple to write down, it is not easy to translate into a form that can be used readily for
setting out in the field.
Setting out the transition curve:
The curve that has now been formed is composite in nature, i.e. it contains a number of different curves, which are designed to fit together. There is a transition curve at each end and a central circular portion. As a whole, the
composite curve is symmetrical, though it should be remembered when setting out that, unlike a circular curve, transition curves are not themselves symmetrical – one end has a greater radius of curvature than the other, so they are not reversible!
A transition curve can be set out in exactly the same way as a circular curve, i.e. by setting up a theodolite at the tangent point, aligning the telescope with the Intersection Point, swinging through the appropriate angles and taping
chords between consecutive pegs. This is the simplest method, and the one on which the calculations are based. Other methods can be adopted, such as setting out using a Total Station set up off the curve, or from a point other than the
tangent point for some practical purpose; however, in each case the same initial calculations are made and then adapted to suit as required.
In order to derive suitable equations relating chord length and deflection angle, we must examine the shape of the transition curve. First, look at it in terms of orthogonal co-ordinates, using the tangent as a reference axis:
Figure: Co-ordinates of the transition curve. Imagine a point some distance, l, along the curve from the tangent point. It will have co-ordinates X and Y as shown in
figure 4 and the angle between the tangent and the line joining T1 and p is . Direct calculation of for specific values of l (i.e. chainages) requires the use of tables of standard data, though such calculations would be made now by
computer. For hand calculation, a series expansion of the clothoid is available:
X = l - l5 + l9 - l13 +….. 40(RL)2 3456(RL)4 599040(RL)6
Y = l3 - l7 + l11 -….. 6RL 336(RL)3 42240(RL)5
tan = + 3 - 5 + 7 -….
3 105 5997 198700
These are clearly impractical. However, for values of up to about 3, the higher order terms can be neglected,
resulting in simpler formulae from which setting-out data can be readily calculated:
Cubic Spiral: Y = l3/6RL = /3
Cubic Parabola: Y = X3/6RL = /3
These are sufficiently accurate for most applications where hand calculation is likely to be employed, and the following procedure is based upon the cubic spiral, which is a better approximation to the clothoid.
X
Y
p
T1 Entry
tangent
T1
3.1.1. Setting-out calculations for the cubic spiral
The equations in the above section allow us to calculate the deviation angle (i.e. the angle set on the theodolite when it is set up at the tangent point) directly. Note that, unlike the circular curve calculations, this is not cumulative.
Deviation angle = /3 = l2/6RL (radians)
i.e. = 180 l2
6 R L
The tangent length of the composite curve (i.e. transition + circular + transition) will be needed for setting out the first
tangent point, T1, and for calculation of the chainages of setting out points. It is obtained by first considering the
properties of an equivalent circular curve, which has the same centre as the circular portion of the curve to be set out, but has a slightly larger radius. The relationship between the two curves is shown in the following diagram:
Figure 5: Equivalent circle and shift for a composite curve.
It can be shown that the line OQ, from the centre of the circle to the tangent point of the equivalent circle, bisects the transition curve T1 T1 and that the shift, S, is
S = L2 / 24R
From the dimensions of the equivalent circular curve, we can obtain its tangent length, distance QI:
QI = (R + S) tan (/2)
Q
S
I
T2 T1 T1 T2
O
R
And, since length T1Q is half the length of the transition curve, we can write
T1I = L / 2 + (R + S) tan (/2)
This allows us to establish the chainage of the first tangent point T1 and hence the distance from the tangent point to
the chainage pegs along the transition curve as well as the chainage of the tangent point to the circular curve, T1.
The circular portion of the curve:
The central circular arc can be set out in exactly the same way as a purely circular curve, i.e. from the tangent point using theodolite and tape. The difference in the case of a composite curve is that the tangents to the circular arc are not
the same as the entry and exit tangents for the composite curve – the intersection angle will be lessened and the point at which they intersect will be closer to the curve than the point I, as shown in the diagram below.
Figure : Geometry of the circular portion of a composite curve.
It can be seen that the angle of the circular arc is
C = 2
Hence the length of the circular arc is
LC = R C
180
This allows the chainages of the two remaining tangent points, T2 and T2, to be calculated. After calculating the positions along the circular arc of the chainage pegs, (cumulative) deflection angles for the entry and exit sub-chords
and the standard chord are calculated in the usual way: d = 28.648 lC / R
The curve can now be set out by setting up the theodolite at T1 and taping between pegs. In order to do this we must
establish the orientation of the tangent, since we can no longer sight onto the Intersection Point, I. This can be done by looking at the geometry of the transition curve.
I
T2 T1 T1 T2
O
-
2
R
Figure 7: Transition curve and Back Angle.
From the properties of the cubic spiral, we know that
= / 3
and the back angle can therefore be calculated as
back = 2 / 3
angle
The theodolite can therefore be oriented at T1 by sighting back to T1 and turning the alidade through 180 + 2 /3
(clockwise). The telescope will then be facing along the tangent to the circular arc, ready to continue setting out.
Note that, for a left-hand curve, the alidade must be rotated through 180 - 2 /3 (clockwise). This is because all
of the curve angles will have been reversed, but the theodolite is still graduated in a clockwise direction.
The exit transition:
The entire circular curve has now been set out, assuming that there have been no obstructions, from one tangent point, usually the entry tangent point T1. However, because the transition curve is not symmetrical, the formulae used above
to calculate deviation angle are only valid for angles from the start of the transition, i.e. T1 or T2. We must therefore
move directly to T2 to set out the second transition curve. The position of T2 can be found by linear measurement
along the exit straight from the intersection point, and checked from T1 by measuring the angle between either straight
and the line T1-T2, which should be equal to /2.
Figure: Checking the position of the two tangent points.
It is important to remember that chainage is still running from T2 to T2, even though we are calculating deviation
angles from T2 to T2 and, in all probability, setting out from T2. Also worth checking in the field with the theodolite
T2 T1
I
required
orientation
Tangent to
circular arc
back
angle
T1
Entry
tangent T1
/
2
/
2
set up at T2, before the transition is set out, is the position of T2. The formula used to calculate deviation angles in the
second transition is exactly the same as before, except that it will be of the opposite hand.
Calculation & observation:
Radius of circular curve= 150m ∆= 48˚48’
C=.45m/s3
Ch. of I.P= 2575.37m Peg interval not greater then 10m
Design velocity = 60 km/hv = 60 * 1000 / 3600 = 16.67m/s
Computation:
Length of transition curve= L = V3/3π = 68.63m/s Xc= 68.03m Yc=L2/6R=5.23m
∆/2 = 24˚24’ Φc=L/2R rad. =1306’27”
Ϭ= L2/24R = 1.31 α = 155˚36’
center of circular arc = 22˚35’06” length of circular arc = π R(22˚35’06”)/180 = 59.3m
tangent length= Xc + ( R + Ϭ ) tan∆/2- R sin Φc = 102.65 ϴ = l2/6RL rad . when l is length along transition
Ditection of tangent at c1 NC1H = 360 – (1/2 central angle + α + 90) =103˚06’27”
Chainages:
Ch. of T1= 2575.37-102.65=2472.72m Ch. of C1= 2472.72+ L=2541.35m
Ch. of C2=2541+lg + circular arc=2600.48m Ch. of T2= 2600.48 + L=2669.11
Detail:
For circular curve each deflection angle = 1718.9 * C / R minutes AT1=Tangent length = 102.65 m T1T2 = (102.65/sin24˚24’) *sin 24˚28’ = 186.96 m
1. Table For Setting Out Transition & Circular Curve:
Procedure: 2. Set two points T1,T2 at 186.96 m apart. 3. Erect poles in direction from T1 to T2.
Transition T1C1 Circular arc C1C1 Transition T2C2
Ch
ain
ag
es
M
l
(m)
Total
def.
angle
Angl
e to
be
set
on
thed
olite
Chainages
(m)
Ch
or
d
(c)
(m
)
Each
def.
angle
Total
def.
Angle
Angl
e to
be set
on
thedo
lite
Chainages
m
l
(m)
Total
def.
Angle to
be set on
thedolite
24
72.72 (T
1)
0 0 0 254.31 (C1) 0 0 0 0 2669.11 (T2) 0 0 0
2480
(P1)
7.28 0˚2’57” 0˚2’55”
2550 (P1) 8.65
1˚39’7” 1˚39’7”
1˚39’5”
2660 (P1) 9.11
0˚4’37” 0˚4’35”
24
90 (P2)
17.28 0˚16’37” 0˚16
’35”
2560 (P2) 10 1˚54’36
”
3˚33’4
3”
3˚33’
45”
2650 (P2) 19.
11
0˚20’20” 0˚20’20”
25
00 (P3
)
27.28 0˚41’24” 0˚41
’25”
2570 (P3) ˶ ˶ 5˚28’1
9”
5˚28’
20”
2640 (P3) 29.
11
0˚47’10” 0˚47’10”
2510 (P4
)
37.28 1˚17’21” 1˚17’20”
2580 (P4) ˶ ˶ 7˚22’55”
7˚22’55”
2630 (P4) 39.11
1˚25’8” 1˚25’10”
2520
47.28 2˚4’24” 2˚4’25”
2590 (P5) ˶ ˶ 9˚17’31”
9˚17’30”
2620 (P5) 49.11
2˚14’14” 2˚14’15”
25
30 (P6
)
57.28 3˚2’37” 3˚2’
35”
2600 (P6) ˶ ˶ 11˚12’
7”
11˚12
’5”
2610 (P6) 59.
11
3˚14’28” 3˚14’30”
2540 (P7
67.28 4˚11’56” 4˚11’55”
2600.42 (C2)
0.48
0˚5’30” 11˚17’37”
11˚17’35”
2600.48 (P7) 68.63
4˚22’9” 4˚22’10”
25
41.35
68.63 4˚22’9” 4˚22
’10”
4. Start setting out from T1 for first transition curve. 5. Start setting out from T2 for 2nd transition curve.
6. Set out circular arc C1C2 using table of setting out for circular curve.
Job # 07
Title: To Design And Set Out Of A Vertical Curve
Objective: The objective of this survey is to design and set out a vertical curve.
Apparatus: 1. 5 sec Transit Theodolite
2. Ranging Rod
3. Tripod Stand
4. Automatic Level
5. Leveling stave
6. Pegs
7. Wooden Hammer
8. Measuring Tape
Related Theory:
1. Theodolite: It is an instrument which is used mainly for accurate measurement of horizontal and vertical angles. The least count of this theodolite (TOPCON DT-104) is 5” but can be changed by changing the settings.
2. Ranging Rod: It is a long metal or wood bar with noticeable markings and colors (usually it is painted in red and white stripes). In this
Experiment, it will be used to mark the station point and to make it easier for the station point to be sighted with the
prismatic compass.
3. Tripod Stand: It may be wooden or metallic. It is three-legged and the Prismatic Compass is fixed on it with the fixing knob. The
Prismatic compass is centered and levelled on the stand prior to sighting.
4. Automatic Level: This is also called as self-aligning level. This instrument is leveled automatically within a certain tilt range by mean of compensating device (The tilt compensator)
5. Leveling Stave:
The leveling stave is graduated rod used for measuring the vertical distance between the points on the ground and the line of collimation.
6. Pegs: It is used to mark point on the ground.
7. Wooden Hammer:
It is used to insert pegs into the ground.
8. Fiber Glass Tape: It can be graduated in different scale like meters or feet. It can be metallic or fiber glass tape. In our case it is fiber glass
tape. Its length is 30m or 100 ft.
Procedure: Set up theodolite at any point before station A, mark the calculated intervals in the line of peg A. Afterwards mark the next points at a distance x from the station A at 20m. Find the value of radius, chainages, and levels by using the
following formulas. Place the instrument level at any point a little away from the line of sight and find the values of level of all the stations. Then, find the MSL as shown in the table.
Chainages:
I= 2325.0 m A= 2325.0 – (127.84/2) = 2261.08 m
C= 2261 + 127.84 = 2388.92 m
Chainag
e x(m) Level on
Tangent
(Z)
y Level on
parabola (Z-
y)
MSL
2261.08 0 213.15 0 213.15 213.1
5
2280 18.92 213.72 .07 213.65 213.87
2300 38.92 214.32 .29 214.03 214.4
4
2320 58.92 214.92 .68 214.24 214.74
2340 78.92 215.52 1.22 214.30 214.5
4
2360 98.92 216.12 1.91 214.21 214.26
2380 118.92 216.72 2.76 213.96 213.77
2388.92 127.84 216.98 3.19 213.79 214.49
Precautions: Following precautions should be taken into account while performing the survey.
ld be accurate.
nt.
Job # 07
Title: To Design And Set Out Simple Circular Curve
Objective: The objective of this survey is to design and set out a vertical curve.
Apparatus:
1. 5 sec Transit Theodolite
2. Ranging Rod
3. Tripod Stand
4. Pegs
5. Wooden Hammer
Related Theory: 1. Theodolite:
It is an instrument which is used mainly for accurate measurement of horizontal and vertical angles. The least count of this
theodolite (TOPCON DT-104) is 5” but can be changed by changing the settings.
2. Ranging Rod: It is a long metal or wood bar with noticeable markings and colors (usually it is painted in red and white stripes). In this
Experiment, it will be used to mark the station point and to make it easier for the station point to be sighted with the prismatic compass.
3. Tripod Stand: It may be wooden or metallic. It is three-legged and the Prismatic Compass is fixed on it with the fixing knob. The Prismatic
compass is centered and levelled on the stand prior to sighting.
4. Pegs: It is used to mark point on the ground.
5. Wooden Hammer:
It is used to insert pegs into the ground.
Procedure: Mark a point on the ground with the help of peg and set up the instrument theodolite on it.
After centering, leveling and focusing of the theodolite mark point T2 at the specified distance.
Fix a ranging rod at I so that angle IT1T2 is Φ/2. Now bisect I and set the 1st small deflection
angle, rotate the theodolite and clamp the horizontal clamping screw, this will set the line of
sight, now measure length of first sub-chord and mark the peg by guiding it from the
theodolite. Swing till the rod bisected by the vertical hair of theodolite. Repeat the procedure
each time setting the deflection angle for each point and measuring the distance from the
previous point.
Steps For Curve Calculation Data:
Following formulas are used for setting out of curve.
Length of circular curve= πRΦ/180
Length of long chord= 2Rsin(Φ/2)
Tangent Length= Rtan(Φ/2)
Chainage of T1= Chainage of I – Tangent Length
Chainage of T2= Chainage of T1 + Length of circular curve
Length of initial sub-chord
Deflection angle for initial sub-chord= 1718.9(C)/R ; C=Peg Interval
Deflection angle for full chord=1718.9(C)/R ; C=Peg Interval
Deflection angle for last sub-chord=1718.9(C)/R ; C=Peg Interval
Observations table: Radius of curve= 120m
Φ= 40o
Chainage of I= 5755.67m
Point Chainage Chord Length
Deflection Angle for Chord
Total Deflection Angle
Angle to be set
Remarks
T1 5712 0 0 0 0 Starting point
P1 5720 8 1o54’35’’ 1o54’35’’ 1o54’35’’ 1st Peg P2 5730 10 2o23’14.5’’ 4o17’49.5’
’ 4o17’50’’ 2nd Peg
P3 5740 10 2o23’14.5’’ 6o41’4’’ 6o41’5’’ 3rd Peg P4 5750 10 2o23’14.5’’ 9o4’18.5’’ 9o4’20’’ 4th Peg P5 5760 10 2o23’14.5’’ 11o27’33’’ 11o27’35’
’ 5th Peg
P6 5770 10 2o23’14.5’’ 13o50’47.5’’
13o50’45’’
6th Peg
P7 5780 10 2o23’14.5’’ 16o14’4’’ 16o14’5’’ 7th Peg P8 5790 10 2o23’14.5’’ 18o37’16.
5’’ 18o37’15’
’ 8th Peg
T2 5747.77 5.77 1o22’39’’ 19o59’55. 19o59’55’ Ending
5’’ ’ point
Precautions:
Following precautions should be taken into account while performing the survey.
Calculations should be done with great care.
Centering, levelling and focussing of instrument should be accurate.
Peg should be inserted in the ground at the exact point.