Surveying

1. DEPARTMENT OF CIVIL ENGINEERING
PRESENTATION BY
SHANMUGASUNDARAM N
ASSISTANT PROFESSOR
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Shanmugas
undaram.N

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CE6404-Surveying II/Unit II by,
Shanmugasundaram.N
TOTAL STATION

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PARTS OF TOTAL STATION

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prism

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Equipments

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Introduction
 Total station or electronic tachometer = Electronic
theodolite (Electronic distance measuring devices EDM) +
Microprocessor with memory unit.
It has helped to set the stage for modern data collection
and processing.
Its introduced and famous at the year of 1960’S by carl
zeiss.

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Basic principle:
 Telescope is attached to scales for measuring the angles of
rotation of telescope (Normally at N).
Rotate the telescope to aim at a target and note the angles.
The EDM instruments transmits an infrared beam which is
reflected back to the unit with the help of the prism.

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Cont....
The EDM calculated the distance by the time.
Microprocessor used to store the data and instruments can
display the sloping distance, horizontal and vertical distance,
difference in elevation and coordinates.
It is used to reduced error and recollect the data's.

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Classification or types of Total station:
Manual Total station
Semi-automatic Total station
Automatic Total station
Servo-Driven Total station

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Manual Total station
Oldest total station
Necessary to read the horizontal and vertical angles manually
Only Slope distance read electronically
Semi-automatic Total station
Horizontal circle had to be read manually and vertical circle
readings where shown digitally
Slope distance read electronically

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Automatic Total station
Commonly used
Read automatically Slope distance, Horizontal, vertical
distance, angles coordinates etc..
Servo-Driven Total station
Advance of automatic total station.
Its suitable for intense mapping.
Auto tracking feature is the recent advancement.

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Electro optical EDM system:
Its mostly used by the civil engineers
The measure length varying from 1km to 60km.
As with microwave instruments all need line of sight
conditions.

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The main components are
1. A light sources
2. Visible light
3. Produced by the tungsten lamp
4. Xeon flash tube or laser light or infra red light
5. A light modulator
6. Optical parts for transmitting and receiving the modulated
light
7. Photomultiplier ,phase meter and a readout unit.

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Most short-range instruments were introduced after the
development of luminescent gallium arsenide diode.
This diode emits an infra red carrier beam which can be
amplitude modulated directly, because the intensity of light
emitted is proportional to the current fed to the diode.
The infra-red beam is reflected at the remote station, normally
by a prism and returned to a photodiode.

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The alignment between the infra-red beam and prism is the
only problem.
To introduce 360 degree prism to reduce the problem.
All the EDM systems measure the slope distance (s) along the
carrier wave.
Set the pole with based on the ground.
H = S cos θ also V = S sin θ

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Microwave EDM system:
Important position in land surveying because its measured
from 50m to 50km
Measurements consist of both ends with uses master at one
end and remote at other end.
An operator is required at each inter communication being
possible by means of built in radio telephones.

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Cont....
Signal is transmitted from master received by the remote and
transmitted back to the master
This displays is usually calibrated to read out directly in metre.
Operators are major roll in this method.
Carrier wave adopted typically about 10GHz –W.length 0.03m
Frequency modulation 7.5 or 15MHz
Phase resolution 0.1% - Basic position about 0.01m.

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EDM principle:
1. Pulse method
2. Phase difference method
 All the equipment are based on the principle that the distance
D is equal to the product of velocity (v) and time (t).

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Pulse method:
 Its simple concept that the distance is a product of velocity and
time.
Radiation is transmitted to a reflector target and transmitted back
to the receiver along a parallel path
Distance is measured by velocity of the signal and the complete
time taken for the travel.

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Cont.....
Distance is depending on the velocity of light and time
Considering approximate value of 3x10 6 m/s
Speed light 10-10s
Equal to 15mm distance
The distance that can be measured is largely a function of the
power of the pulse.

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Phase difference method:
 Speed of light in vacuum is well known but the measurements
are taken not in vacuum thus correction for atmospheric conditions
are to be made.
The greet speed of the light it is not possible to directly measure
the time taken for the travel.
To solve this problem by phase difference between the
transmitted and received signals.

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Cont....
 difference wave lengths are used to determine the distances.
EDM instruments whether infra-red or microwave adopt this form
of measurement.
Electro magnetic waves are transmitted to a retro-reflector (single
or multiple prisms) which immediately return back to the
transmitting instruments.
Distance calculated and comparing the phase shift of the
transmitted and the reflected signals and the time.

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Working principles of Total station:
1. Salient parameters
2. Setup of a Total station
3. Setting up a back sight with Total station
4. Initial setting of Total station
5. Measurement of angle and distance
a) Horizontal angle
b) Vertical angle
c) Slope distance

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Salient parameters:
 The total station measures horizontal angles and vertical angles of
the LOS from the centre of the instrument to the target on a point to
measure.
The CPU computer coordinate (E,N,H) and refer total station
coordinate (Eo,No,Ho) and using the measured polar coordinates
(SD,Hz,V) instrument height, target height, several correction factors
and constants.

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Setup of a Total station:
 An adequate instrument station is chosen.
Necessary precautions are to be taken in locating the station for the
comfortable use of observer.
Tripod are stretched and levelled at comfortable height.
Fix the centring at use of tripods legs.
Fix the Total station at the head of tripod with a built-in plummet.
Adjust the three screws by adopting the conventional procedure.

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Cont......
 switch on the laser plummet and rotate the Total station to check
the cantered within 1cm from the reference point.
Use the plate level for final levelling and check the centring.
Rotate the Total station at 180º and check the centring and adjust
by using fixing screws.
Check the instrument height and check the plate level during
measurement at time to time

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Setting up a back sight with Total station:
 A BS is the reference point for the horizontal angle.
At beginning of new survey a BS can be set at an arbitrary point
and marked
Use prism at BS and measure target height at after levelling and
centring
Measure the Azimuth for 0º to 360º from clock wise from north.

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Initial setting of Total station:
 Total station is turned
Both H and V screws are released.
Eliminate parallax.
Rotate alidade ( Sokkia model only) and use the hold key.
Aim the prism and lock the H and V drives.
Use the hold key and rotate the instrument the angle will be
changed.
Fix the Eo, No and Ho when the instrument is changed.

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Cont.....
 pointing the prism is again checked
Use the distance measurement key and calculate the all necessary
coordinates.
All data is stored to memory like a file and set another job for other
experiments.

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Measurements of angles and distances:
1. Horizontal angle:
Measures from zero direction on the horizontal circle.
Made as instrument at north direction.
Fix approximately true magnetic or grid north.
It is used to recovered if the instrument was setup at the same
location at some later date.
Most total station can measured angle at least 5ʺ or 0.0013888º

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Measurements of angles and distances:
2. Vertical angle:
It is used to measured as a zenith angle.
Fix the instrument at exactly vertical.
Total station have an internal sensor to detect the same deviations.
The compensator works electronically can make small adjustment.

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Measurements of angles and distances:
3. Slope distance:
It is measured using the inbuilt EDM.
Most EDM use a gallium aresnide diode to emit an infrared light
beam.
This beam is modulated to two or more difference frequencies
Use the reflector and measure the distance and required data

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Sources of errors in Total station:
Two side measurements are eliminate errors at sometimes.
One side measurement need to corrected them.
1. Horizontal collimation or Line of sight error
2. Vertical collimation or vertical index error
3. Compensator index error
4. Tilting axis error

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Horizontal collimation or Line of sight error:
Line of sight is not perpendicular to the tilting axis.
Its affected by all readings
Correction is applied for all horizontal circle reading
If C is exceed a specified limit, the total station should be returned
to the manufacturer.

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Vertical collimation or vertical index error:
 When the 0º and 180º line in the Vertical circle does not coincide
with its vertical axis.
 Its present in all vertical circular readings like horizontal
collimation error.
 This error solve by FL and FR readings.

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Compensator index error:
During the face left and face right measurement the level are not
maintained properly.
Measure the error and apply correction at when the compensators
was fixed.
If the the error at both(l and t) side, consider for zero point error
and its eliminated by face left and right observations.
Single error must be determine by calibration(H and V
rotation)function of total station

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Tilting axis error:
When the tilting axis of the total station is not perpendicular to its
vertical axis.
Its not affected at telescope is horizontal but occurs at tilting the
telescope. Especially for steep sighting.
Its eliminated by two faces or measure the error and apply
correction.
In case of the error is big returned to the instrument

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Target prism:
Its used to reflect transmitted signals.
It is cube corner prism is formed by cutting the corners off a solid
glass cube.
Its perpendicular to the 90º surface.
Attached by the prism pole with eye level. Marked by heights.
Some times used for tripod for alternative to pole.

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Merits of total station:
Setting is easy using laser plummet.
On-board area computation programme to compute the area of the
field.
Grater accuracy
Automatic mapping, calculation data and dimensions is easily
taken.
Plotting and area computation are possible for any scale.
Storage capacity and old maps are automatically done.

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Demerits of total station:
Hard copies of field notes are not possible.
Difficult to check the work during surveying.
Cost is high.
Need skilled persons.
Cannot use routinely by sun.
Checking only in software.

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Comparison between Electro-optical and microwave system:
ELECTRO OPTICAL SYSTEM MICROWAVE SYSTEM
Length measured from 1km to
60km
Length measured from 50m to
50km
Mostly used in civil engineers at all
the areas
Mostly used in land surveying
Used by infrared beam reflected at
the remote station
Signal is transmitted from master,
received by the remote and
transmitted back to the master.
No need communication or less
communication required to
operator.
An operator required
communication by means of
built-in ratio telephone.

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Comparison between Electro-optical and microwave system:
ELECTRO OPTICAL SYSTEM MICROWAVE SYSTEM
Measurements are directly readout
in any units
Measurements are directly
readout in metre by using display
Maintaining alignment between the
infrared beam and the prism is
difficult
Maintaining alignment between
the infrared beam and the prism
is easy comparing to EOS
Operational is little difficult need
skilled persons.
Operational is simple and
recording the job is also in simple
manner.
Low frequencies High frequencies

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Care and maintenance of total station instruments:
Its involve in identifying calibration parameters, sources of error
and the procedure for calibration.
Calibration norms of total station
High level accuracy is depends on monitoring instrumental errors.
Check the instruments at regular basis.
Errors are identified and corrected using electronic calibration
procedure at any time

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Cont....
Calibration parameters can change due to mechanical shocks,
temperature changes and roughly handling instruments.
The important parameters are:
Before using the instrument for the first time.
After long storage periods
After rough or long transportation
After long period of work
Big changes in temperature
Regularly for precision survey
Allow the enough temperature at before each calibration.

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Traversing and Trilateration using total station:
Traversing:
Use this method when it is not possible to view the entire mapping
area from the first station.
Procedure:
Set the prism to the tripod or pole and doing for centring and
levelling
Measure BS, measure EI, NI and HI and necessary data's,
The Total station and prism is exchanged. etc...

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Trilateration :
Its basically a technique of triangulation
No angular are made
3 sides of the triangles are measured precisely using EDM or Total
station
Its useful when the measurements are difficult or impossible due to
any reason.
Geometry is same as per triangulation
It has several disadvantages.
Accuracy is depends on vertical angle.
Procedure is similar to the traversing

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Electronic distance measurement (EDM)
Used to measure the distance accurately.
Measures long distance to an accuracy of a few mm.
Its available at total station instruments.
Its identify the namely Electronic type and microwave
In each cases the velocity of the electromagnetic waves in are must
be known precisely
Sending continuous waves to a receiver at the other end.
This waves are termed as carrier waves.

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Feature of total stations:
 Capable of measuring angles and distance simultaneously and
combine an electronic theodolite with a distance measuring system
and microprocessor
Angle measurement:
Levelling is carried out in the same way as for a theodolite.
Use both faces
Use horizontal clamping and tangent screws
Rotate the instruments and note the angles in the same way as the
electronic theodolite.

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Distance measurement:
Distance taken to a prism or reflecting foil,
Its taken for 1 to 2s and range of 3 to 5km to a single prism
Accuracy 2mm + 2ppm
For long distance use GPS preference to total station
Readings are measured quickly
Without using prism we can able to calculate 100m accuracy.

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Key board and display:
LCD placed at both sides attached with key board.
Some of the total station key board are able to inter change to other
This is called integrated surveying.
Software applications
Micro processor used to measure angles and distances
LCD screen is used to control or operating for Total station
Slope correction & reduced levels, horizontal circle orientation,
coordinate measurement, traverse measurement, resections, remote
elevation measurement, area, setting out and etc...