SURVEYING-LEVELING-MODERN SURVEYING INSTRUMENTS

VISHNU VIJAYAN
HOD-Department Of Civil Engineering
Baselios Mathews II College Of Engineering
Sasthamcotta, Kollam,Kerala,INDIA

CONTENT
 In this module we are going to learn about
➢ 1. SURVEYING
➢ 2. LEVELING
➢ 3.MODERN SURVEYING INSTRUMENTS
26 March 2020 2VISHNU VIJAYAN BMCE

SURVEYING

SURVEYING
 Surveying is the art of determining the relative positions of
points or objects on, above or beneath the surface of the earth by
means of direct or indirect measurements of distance, direction
and elevation in a horizontal or a vertical plane.
 The main object of a survey is to prepare plan or map of the area
to be surveyed. A plan or map is the horizontal projection of an
area and shows only horizontal distances of points.

Objectives or purpose of survey
1. To determine the relative positions of the existing
futures of the ground.
2. To layout our marked positions of proposed
structures on the ground.
3. To determine areas, volumes and other related
quantities.
4. To prepare a map of a country of detailed location of
cities, towns, villages and major roads.
5. To prepare the engineering detailed plans and
sections of various sections such as roads, railways,
bridges, dams and other structure.
6. To prepare a topographical map showing details of
hills, valleys and rivers.

Types of surveying :
 Primarily, surveying can be divided into two classes
1.Plane surveying:
The earth is assumed to be spheroid in shape. In plane
surveying the curvature of the earth is neglected, assuming
the earth’s surface is plane and the line joining two points on
the surface is considered as straight line and the triangle
joining any three points as plane triangle.
2.Geodetic surveying: In Geodetic surveying the curvature
of the earth is taken into consideration and hence high
degree of accuracy is obtained. It is used when survey’s
extent over large areas. The line joining any two points on the
surface of the earth will be a curved one. And the triangle
considered as a spherical triangle. Geodetic survey is used
when survey extend an area more than 260 km 2

General classification of surveying
1.According to instruments used: Chain surveying , Compass
surveying, Plane table surveying , Theodolite surveying ,
Tacheomeric surveying etc…
2. According to the purpose of survey
 Mine surveying- To explore minerals
 Geological surveying-Study about earth’s crust
 Archaeological surveying-To study the past
 Military surveying – to study the places of strategic importance
3.According to the place of work
 Land survey - survey on earth’s surface
 Marine survey – Survey in sea
 Aerial survey – Survey in air

PRINCIPLES OF SURVEYING
The fundamental principles of surveying is
(1) To work from whole to part
(2) To locate a point by taking
measurements from two reference points.
To work from whole to part: this is the
main principles of surveying .here the
entire plot will be divided into smaller
triangles and the area will be surveyed from
the boundary to the innermost triangle. The
purpose of working from whole to part is to
localize the errors and to control the
accumulation of errors.

CONTD..
To locate a point by taking measurements from two
reference points:
Two control points are selected in the area and the
distance between them is measured and plotted on a
paper. All other points are marked based on these two
points.

HORIZONTAL MEASUREMENTS
 In surveying linear measurements or distances can be
determined by two ways namely direct method and
computative methods.
 In the direct method , the distances are measured
physically on the ground using instruments like chain, tape
etc.
 In the computative method , the distances are obtained by
calculations like in tacheometry, triangulation etc.

Chaining :
 This is the most accurate and common method for
measuring distances.
 Chaining is the term which is used to denote
measuring distances with a chain or tape .
 The chain is used for ordinary work . Where more
precision is required , steel tape is used.

INSTRUMENT USED FOR
SURVEYING
 CHAIN :
 Chains are formed of a number of links made up of
galvanized mild steel wire of 4 mm diameter. Each end
of a link is bent up into a loop . The links are
connected in series by small oval shaped rings with a
central circular rings. These rings provide flexibility to
the chain.

CHAIN :

There are mainly two types of chains
1.Metric chain: Metric chains are available in lengths
5,10,20 and 30 meters. The distances are measured in
metric units. In case of 20 m and 30 m chains , small
brass rings are provided at every one meters interval
and tallies are provided at 5m and 10 m intervals .

Non metric chain:
 The commonly used non metric chains are
 Gunter’s chain or Surveyor’s chain : These are 66
ft. long and consists of 100 links. Each link being0.6
ft or 7.92 inches long. Distances are measures in
miles and furlongs.
 Engineer’s chain : These are 100 ft long and
consists of 100 links. Each link being 1 ft long.
Distances measured are recorded in feet and
decimals.
 Revenue chain : The revenue chain is 33 ft long
and consists of 16 links, each link being 2
1
16
ft long.

TAPE
 Tapes are used for more accurate measurements and
are classified according to the material used for
manufacturing them. Mainly they are of four types.

TYPES
1.Cloth or linen tape : It is made of linen cloth.
A cloth tape is commonly available in lengths 10
m, 20 m , 25m and 30 m and in 33 ft,50 ft, 66ft and
100 ft.
The width of tape is 12 to 15 mm.The end of tape is
provided with a small brass ring whose length is
length is included in the total length of the tape.
It is ligtht weight when compared with chain .
but it is rarely used for making accurate
measurements because (a) it is easily affected by
moisture or dampness (b) it is likely to twist and
tangle (c) the length get altered by stretching (d)
it is not strong.

Metallic tape:
 It is a linen tape with brass or
copper wires woven into it
longitudinally to reduce stretching.
 The metallic tapes are light and
flexible and are not easily broken.
 These are available in lengths of
2,5,10,2.,30 and 50m having width
16 mm.
 A metal ring is provided at the
outer end on which the length of
tape marked. In this type every
centimeter marked by black lines,
every 5 cm marked by black arrow,
Every decimeter in black figures
and meters in red figures.

Steel tapes
 Steel tapes are better than cloth
or metallic tape.
 A steel tape consists of a light
strip of steel of width 6 to 10
mm and is more accurately
graduated.
 Steel tapes are available in
lengths of 1,2,10,20,30 and 50 m
. These types are also provided
with a metal ring at ends.
 It is mainly used for measuring
chain length and measurement
of buildings.

Invar tape :
 It is alloy of steel(64%) and
nickel(36%) called invar. Due to its
low thermal conductivity error due to
temperature fluctuation is minimum.
 It is used for linear measurements of
a very high degree of precision.
 It is 6 mm wide and is usually
available in length 20,30 and 100m . It
is more expensive.26 March 2020 20VISHNU VIJAYAN BMCE

RANGING
 The process of establishing intermediate
points on a straight line between the
terminal points or two station points is
called Ranging.
 The instrument used for ranging out a
survey line are called Ranging rods.
There are TWO METHODS OF
RANGING
(1) Direct ranging (2) Indirect ranging

DIRECT RAINGING METHOD:
 Rainging is called direct, when intermediate ranging rods
are placed in line by direct observations. It is done only
when the two terminal points of survey line are mutually
inter visible. Direct ranging can be done by 2 methods:

1.RANGING BY EYE:
2.RANGING BY LINE
RANGER:
 A line ranger is a small
reflecting instrument
used for rainging long
lines without going to one
end of line and sighting
from it.

INDIRECT RANGING :
 It is also called reciprocal ranging. When intermediate
ranging rods are placed in line with two end stations
which are not intervisible due to high ground or hills,
in such case ranging is done indirectly by selecting
intermediate points between station points. Such type
of ranging is called as indirect ranging.

Review questions
1. What are the main objective of surveying?
2. Write short note on principles of surveying
3. Different methods used for measuring
horizontal distances?
4. Define ranging out of a survey line?
5. Explain the different types of tapes used in
surveying
6. Explain various method used for direct ranging?

LEVELLING
 Leveling is a branch of surveying.
 It is the process of determining the relative heights or
elevations of points or objects on the earth’s surface.
 The elevation of a point is its vertical distance above or
below a reference level called datum.

Objectives/Purpose of Leveling
1. To find the elevations of given points with respect to
a given or assumed datum.
2. For design of highways ,railways canals etc
3. For locating excavating levels
4. Preparation of contour maps..

Principle of leveling
 The principle of leveling is to
obtain horizontal line of sight
with respect to which vertical
distances of the points above or
below this line of sight are found.
 The telescope when rotated in any
position, the line of sight remains
in the horizontal plane
 Thus if the telescope is sighted
towards a staff kept on a point of
known elevation, the height or
elevation of the line of sight can
be determined
 If the telescope is now directed to
staffs kept on points of unknown
elevation, the staff readings can
be read, from which the reduced
levels of the unknown points can
be determined.

TERMS USED IN LEVELLING
 Level surface: A level surface is defined as a curved
surface which at each point is perpendicular to the
direction of gravity at the point.
 Level line: A level line is a line lying in a level surface. It
is, therefore, normal to the plumb line at all points.
 Datum: Datum surface or datum is any arbitrarily
assumed level surface from which vertical distances are
measured. In India ,the datum is mean sea level at
Bombay Port( Previously it was mean sea level at
Karachi)
 Elevation: The elevation of a point on or near the
surface of the earth is its vertical distance above or
below an arbitrarily assumed level surface or datum. It is
also called Reduced level (RL).
 Mean sea level(MSL): It is the average height of the sea
for all stages of the tides

 Bench Mark(BM): It is a relatively permanent point of
reference whose elevation with respect to some assumed
datum is known. It is used either as a starting point for
leveling or as a point upon which to close as a check.
 Height of Instrument (HI) : The elevation of the line of
sight with respect to assumed datum is known as height of
Instrument(HI).
Back sight : (B.S.) - The first staff reading taken on a
leveling staff held at a point of known elevation or known
RL is known as back sight.
Intermediate Sight (IS) : The readings taken with a level
other than back sight and fore sight are called intermediate
sight
 Fore Sight : (F.S.) – It is the last staff reading taken from a
setting of the level.
 Change Point (CP) : The point on which both the
foresight and back sight are taken during the operation of
leveling is called change point.26 March 2020 30VISHNU VIJAYAN BMCE

INSTRUMENTS USED FOR
LEVELLING
1. Level,
2. Tripod
3. Leveling staff
4. Tape
5. Pegs
6. Hammer

LEVEL A level is used to provide a
horizontal line of sight .A level
consists of following parts.
 A telescope to provide line of sight
 A level tube to make the line of
sight horizontal.
 A leveling head to bring the
bubble in its center of turn
 A tripod to support the instrument
TYPES OF LEVEL
 Dumpy level
 Wye or Y level
 Reversible level
 Tilting level
 Automatic level
 Digital auto level

TRIPOD
 Tripod is an arrangement which
consists of three legs. It is used for
fixing the level in a suitable position
for leveling process. The three legs
has pointed metal shoes.
 LEVELLING STAFF
 A leveling staff is a straight
rectangular rod having graduations.
The foot of the staff represents zero
reading.
 The purpose of a level is to establish
a horizontal line of sight.
 The purpose of the leveling staff is to
determine the amount by which the
station is above or below the line of
sight .

Checking the level difference

LEVEL FIELD BOOK
 Level field book or a level book is used for recording
the staff readings and calculating the levels of various
points in a systematic way.
 There are two methods for calculating or reduction of
the levels namely
 (1) height of instrument method
 (2) the Rise and fall method..

Exercise:
1. Define leveling?
2. Define fore sight , back sight and intermediate sight readings?
3. What is meant by change point and height of instrument?
4. Define line of collimation and axis of telescope?
5. Write short note on Bench mark?
6. Define principles of leveling?
7. Write short note on leveling staff.
8. How readings are entre in a level field book?
9. Temporary adjustments of a dumpy level?
10. The following readings were taken with a dumpy level
1.905,2.635,3.915,4.205, 1.965,1.705,1.590,1.260,2.545,2.000,3.145 the
instrument shifted after fourth and seventh reading. The RL of first
point is 100.00m .Rule out the page of level field book and do
necessary check.

ELECTRONIC DISTANCE METER (EDM)
 EDM is a small, light weight electronic
equipment used for measuring distances
using light and radio waves.
 It possesses excellent accuracy and
extremely short measuring time Distomat
is an example of EDM, which uses infrared
rays for measuring distances.
 EDM measure distances on the basis of
time measurements or phase difference
between transmitted rays and receiving
rays.
 EDM use three different wave lengths
bands
 Microwave system with range upto 150 Km
 Light wave system with range upto 5Km
 Infrared wave systems with range upto 3
Km

TOTAL STATION

TOTAL STATION
 A total station is a combination of an electronic
theodolite, an electronic distance measuring device and
a microprocessor with memory unit.
 With this device one can determine angles and distance
from the instruments to the point to be surveyed.
 Within the aid of trigonometry the angels and distances
may be used to calculate the actual positions (x, y, z )
 The EDM instrument transmits an infrared laser lights
which is reflected back to the unit with the help of a
prism and the EDM carries timing measurements to
calculate the distance travelled by the beam.
 It can maintain considerable accuracy and is hence used
for many public works such as construction of roads,
airports and harbours.

ACCESSORIES OF TOTAL STATION
 Tripod:
The tripod supports the total station, holding it steady so that the
surveyor can make accurate calculations.
 Prisms and poles:
The EDM sends out an infrared beam to measure the distance
between the total station and another point. A prism makes the
ideal target for this, reflecting the beam back powerfully and
accurately.
Data collector
 Total station have a data collector built in to them. It is a critical
device because it records the surveyor's measurements.
 Battery
 Data cables

ADVANTAGES OF TOTAL STATION
 It is more accurate and less prone to errors arising from
interpolating between marks or from miss recording
because of digitalization of angles
 Errors during measurements are avoided because of
Electronic distance measurements
 Total station consist of a data recording option, this is very
helpful to record data during working and after that it can
be decoded with the help of a computer
 With the help of the calculator assigned with the total
station can perform the trigonometric functions needed
with angles and distances and can locate the sighted points

DIGITAL LEVEL:

 Digital automatic levels are a precise instruments used for
precise leveling.
 Operation of digital levels is based on the digital processing
of video indications of a coded staff.
 At the beginning of measurement a visual pointing of the
instrument into the surface of leveling meter is performed.
 After that the instrument automatically points the focus of
its optical system on the surface of the meter and then a
rough correlation calculation is performed followed by the
precise correlation.
 According to the data received in the processor of the
instrument an exact distance from the axes of the
instrument to the surface of the level meter is calculated.
 According to the information received by decoding the data
from the photoelectric matrix the height of the level placing
is calculated in the processor. During this operation the
coded view of the meter is compared with information that
saved in the memory of the instrument.

GPS

GLOBEL POSITIONING SYSTEM (GPS)
 GPS is a space based radio navigation system with the
help of 24 moving satellites around the earth.
 By using GPS even a common man can get all
information about the different locations, distances,
navigation, time etc.
 The GPS satellites circles the earth twice in a day. That
means every satellite reach same points twice a day.
The GPS system first developed by US for military use
but later it is used for public.
 The GPS system consist of a space element, a control
element on earth, and the GPS receiving element.
 The GPS satellites transmit signals to the earth
received by the GPS receivers and calculate the exact
position of the user by triangulation.
 The basic principle of GPS is same as that of EDM,
that is measure the time between transmitted signal
and receiving signal

USES OF GPS
 GPS helps to calculate speed , bearing, track, trips, sun
rise and sun sets etc very precisely
 It helps for ship movements, movement of air crafts
etc
 GPS provide reliable data anywhere on the surface of
earth with out any discrepancy because it is not
affected by environmental factors like cloud, rain etc
 It is also used for surveying works.

Exercise:
 Write short note on EDM
 Brief discussion about Total station
 Write brief discussion about automatic and digital
levels
 Difference between total station and GPS
 Brief discussion about different modern surveying
instruments.

SURVEYING-LEVELING-MODERN SURVEYING INSTRUMENTS

SURVEYING-LEVELING-MODERN SURVEYING INSTRUMENTS

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