Introduction, electromagnetic spectrum, electromagnetic distance measurement, types of EDM instruments, electronic digital theodolites, total station, digital levels, scanners for topographical survey, global positioning system.

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PREPARED BY : ASST. PROF. VATSAL D. PATEL
MAHATMA GANDHI INSTITUTE OF
TECHNICAL EDUCATION &
RESEARCH CENTRE, NAVSARI.

2.  In surveying, the distance is usually measured directly with a
tape or a chain. This method is known as Direct Distance
Measurement (DDM).
 Fairly good accuracy can be achieved.
 It is difficult when any type of the obstruction is occurred.
 Expensive and time consuming method.
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3.  The distance can be measured indirectly using optical distance
measuring instruments called tachometers. This method is
known as Optical Distance Measurement (ODM).
 Not suitable where high accuracy is required. This method is
used to measure the short distance because the ranging of
tachometer is 100 to150m.
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4.  Electronic Distance Measuring (EDM) instrument have been
recently developed.
 High accuracy distance measured.
 EDM is a one type of the modern instrument to measure the
distance between the two visible point.
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5.  In EDM instruments, the electromagnetic waves are generated
and transmitted. It depends on many factors but principally, on
the nature of the electrical signal used to generate the waves.
 In it, no medium are required and can travels in vacuum.
 EDM method is based on generation, propagation, reflection,
subsequent reception of electromagnetic waves.
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6.  Electromagnetic waves are quite complex in nature. However,
in the simplest form these can be represented as periodic
sinusoidal waves shown in fig.
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7.  The wave completes a cycle in moving from identical points
likeAto E or B to F or C to G or D to H.
 The number of cycles completed by the wave in one second is
called frequency (f) of the wave.
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8.  The length traversed in x-direction by the wave when it
complete one cycle is termed as wave length.
 It is equal to distance which separates two identical point. (λ)
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9.  The time taken by the wave to travel through one cycle, a
distance equal to one wave length is termed as period. (T)
 The velocity (v) of the wave is the distance travelled by in one
second.
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10.  Another property of the wave, known as phase of the wave,
and denoted by symbol Φ is often quoted in degree.
 It varies from 0° to 360° for one cycle.
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11.  The electromagnetic spectrum is shown in fig.
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12.  Electromagnetic waves are energy carrying waves.
 They carry composite energy due to electrical and magnetic
fields.
 Type of electromagnetic waves is known by its wave length
or frequency.
 All the travel with a velocity 3 X 108 m/s.
 These include Y–rays, X–rays, ultraviolet rays, visible light,
infrared rays, microwaves and radio waves.
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13.  There are three type of the waves commonly used in EDM :
 Microwaves
 Infrared waves
 Visible light
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14.  This instrument is used to find the distance between two point
with the help of the EDM. The accuracy of this instrument is
very good as compare the other distance measure instrument.
 Eliminate the chaining and or taping and easy to handle and
operate.
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15.  The basic principle is the indirect determination of the time
required for a light beam to travel between two stations.
 EDM is based upon the measurement of phase difference
between the transmit and received signals.
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16.  Depending upon the type of carrier wave employed, EDM
instruments can be classified under the following three heads :
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Microwave instruments
Visible light instruments
Infrared instruments

17.  First develop in south Africa in 1950s.
 It comes under long range category instruments.
 It’s range is 3 to 30 GHz.
 Transmitted over long distance like 100 km.
 Tellurometer comes under this categories.
 Tellurometer was the first instrument which used microwaves
in measurement of distance for surveying purpose.
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18.  The electro-optical EDM instruments use visible light.
 A geodimeter comes under this type of the categories.
 Range of this instrument is 5 km to 25 km. 5 km during day
time ranging and 25 km in night time ranging.
 The first generation of these instruments was developed in
Sweden in the early 1950s by Dr. Erik Bergstrand.
 Frequencies used in the visible light instrument is of the order
5 X 1014 Hz.
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19.  The instrument in which a beam of light is used as the carries
and which gets back reflected from a kind of mirror located at
the other end.
 At the one end active instrument and one battery are required
and at the other end one mirror provide at the other end.
 They are suitable for small distance measurement.
 In infrared EDM instruments, the near infrared radiation band
of wavelength 0.9 X 10-6 m is used as a carrier wave.
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20.  There are different EDM instruments like :
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Tellurometer
Geodimeter
Distomats

21.  It is an electromagnetic device used to measure distance.
 It was invented by Dr. T.L Wadley of South African National
Institute for Telecommunication Research.
 In this type of the instrument radio waves are used instead of
light waves. System consist of two identical units, master
instrument & remote instrument.
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22.  Two operators can speak to each other using telephonic sets
connected to the instrument.
 The low frequency waves are used for the measurement.
 Master transmitted a series of microwaves and pickup by the
remote. Distance are measure with the help of the radio waves.
 The tellurometer is a first instrument to measure instrument
with light weight power supply of 12 volts or 24 volts.
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23.  A Geodimeter is a first-generation electro-optical instrument,
developed by Dr. E. Bergstrand of Sweden in 1950.
 Instrument use light waves. The instrument has transmitter and
receiver. A 12 volt battery source is essential.
 The light beam is directed on to a reflector at the other end of
the line which is measured.
 The reflector reflect back to the transmitter.
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24.  Distomats are latest in the series of EDM instrument.
 Wild heerbrugg manufacture EDM instrument under the trade
name “Distomat”, having the following popular models :
 Distomat DI 1000
 Distomat DI 5S
 Distamat DI 3000
 Distomat DIOR 3002
 Tachymat TC 2000
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25.  The use of Distomat is similar to that of tellurometer.
 Two instrument are used at both the end of the measured point.
 Communication system is provided.
 The range of instrument is 20 m to 150000 m.
 Distance is automatically displayed on screen.
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26.  They are very precise and convenient to use.
 Design is same as an optical theodolite.
 They contain circular encoders.
 Convert horizontal and vertical angles electronically.
 They display values of angles LCD or LED.
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27.  It is combination of electronic theodolite and EDM.
 The various surveying operations are linear measurements,
angular measurements, elevation measurements, co-ordinate
measurement etc.
 Linear measurement: we use direct or indirect methods of
measuring linear measurements.
 Angular measurement: we use prismatic compass, vernier
transit theodolite, microptic theodolite, electronic digital
theodolite.
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28.  Elevation measurement: we use dumpy level, tilting level,
auto level, digital electronic level.
 Co-ordinate measurement: we run theodolite traverse,
measure lengths, angles and then calculate consecutive and
independent co-ordinates.
 For all the above instrument solution is total station.
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29.  It measures distance and displays horizontal distance and also
slope distance.
 It gives difference in height or elevations.
 It measure the angle and display horizontal as well as vertical
angle also.
 It measure the height above datum.
 It measures coordinates also.
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30.  The total station is equipped with nine type (or more) of
special surveying programs.
 Distance Stake out measurement: By inputting the distance
to be determine by the machine, the difference between that
distance and the actual measured value is displayed.
 Lot staking measurement: The input distance from the
designs or the measured distance, can be divided into N equal
sections, and separate sections measured.
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31.  Offset point measurement: This function enable the widths
to be right and left of a center line to be measured easily, by
setting the instrument on the center.
 Remote Elevation measurement (REM): A prism (base
point) positioned almost directly underneath the desired
location is measured, to determine the height to the target
object.
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32.  Remote Distance Measurement (RDM): This function is
used to measure the horizontal distance, height differential,
slope, distance, and % grade between two points.
 Coordinates measurement: This enables the coordinates of a
target point to be determined, using the instrument point as an
origin point.
 Resection measurement: Two known points (A and B) can
be measured to determine the instrument point coordinate.
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33.  Traverse measurement: Based on given “instrument point
coordinates and backsight coordinates” or on “instrument
point coordinates and directional angle”, the coordinates of a
new point can be determine.
 Coordinates stake out: Based on given “instrument point
coordinates, backsight coordinates and measurement point
coordinates” or on “instrument point coordinates and
directional angle”, three dimensional coordinate carried out.
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34. Control Panel
Angle
Measurement
Distance
Measurement
Onboard
Software
Internal/External
Memories
Data Recording and
Transferring
Power Supply
Accessories
Reflectorless
Distance
Measurement
Graphic
Display
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35.  The main function of GPS system is to provide (Display)
coordinates: Latitude, longitude, elevation above mean sea
level and time, of place occupied by GPS receiver.
 The Global Positioning System (GPS) is a worldwide radio-
navigation system formed from a constellation of 24 satellites
and their ground stations.
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36.  The basis of the GPS is a constellation of satellites that are
continuously orbiting the earth. These satellites, which are
equipped with atomic clocks, transmit radio signals that
contain their exact location, time, and other information.
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