Construction Related Theory for Exercise 4.6.

176
Draughtsman Civil - Total station

Introduction to total station

Objectives : At the end of this lesson you shall be able to
• get introduced to the total station
• learn the evolution of total station from the conventional equipment
• explain the benefits and uses of total station.

General

At present the analogue methods of recording data for

conventional surveying is changed to digital data collection
methods. Previously plane table is used as the best way
to map a small area. But the output of a plane table is just
a low precision anglogue drawing in case of plane table
the map is drawn directly on a sheet in a fixed scale,
there was no way to replot the map to different scales and
the quantity of topographic data collected was few. But
these limitations can be overcome by the use of modern
electronic total stations. With the use of total stations we
can use fastest digital data collection methods.

ed
Definition
bl I
pu M
ish
Total station is an assembly of a short to medium range
Re NI

EDM instrument installed in the framework of an electronic

theodolite with all components under the control of a built-
in micro processor. This single instrument permits
be @

observing distances and directions from a single setup.

o ht

Important parts of total station

t t rig

• EDM with laser generator

• Endless drives
No py

• Trigger keys Features of total station

Co

• Tribrach with foot screws 1 The theodolite is offering a complete product family. It
• Communication side cover is easy fot a user to switch between models without
learning a new operation.
• Bluetooth
2 Absolute circle reading.
• Battery downloading port
3 Excellent hardware features, such as laser plummet,
endless drives on both sides for Hz and V, brilliant
optics with 30x magnification.
4 Dual-Axis compensation for reliable Hz and V reading
5 New and intuitive software.
6 Unique levelling guidence for fast and convenient setup.
7 Hight resolution LCD display.
8 Audible notice for 900 turns and layout.
9 Electronic laser distance measurement.
10 Graphic sketches.
11 Hassle-free EDM measurement with red laser on any
target or on the flar-prism.

183
12 Enter the data at the office and simply call up at the is possible to set required units for distance, temperature
site. and pressure (FPs or SI). Surveyor can select
measurement mode like fine, coarse, single or repeated.
13 Upload and transfer data via on board data connection.
14 Data editing and exchange in total stations. When target sighted, horizontal and vertical angles as well
as sloping distances are measured and by pressing
15 Connectivity to 3rd party devices.
appropriated keys they are recorded along withpoint
Use of total station number. Heights of instrument and targets can be keyed
in after measuring them with tapes. Then processor
The instrument is mounted on a tripod and is levelld computes various information about the point and displays
on screen. This information is also stored in electronic
by operating levelling screws. note book. At the end of the day or whenever downloaded
to computers, the point data downloaded to the computer
Within a small range instrument is capable of adjusting can be used for further processing. There are software’s
itself to the level positon. Then vertical and horizontal like auto civil and auto plotter clubbed with AutoCAD which
reference directions ared indexed using onboard keys. It can be used for plotting contours at any specified interval
and for plotting cross-section along any specified line.

ed
bl I
pu M
ish
Re NI
be @
o ht
t t rig
No py
Co

184 Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.176
Construction Related Theory for Exercise 4.6.177
Draughtsman Civil - Total station

Types of total station

Objectives : At the end of this lesson you shall be able to
• explain the advantages and disadvantages of total station
• explain the types of total stations
• explain the precautions to be taken while using total station.

Advantages of total station Semi-automatic total stations

The advdantagges of total station include: The user had to manually read the horizontal circle for
these instruments, but the vertical circule readings were
1 Quick setting of the instrument on the tripod using laser shown digitally. Slope distances were measured
plummet. electronically and the instruments could, in most cases
2 On-board area computation programmed to compute be used to reduce the values to horizontal and vertical
the area of the field. components.

3 Greater accuracy in area computation because of the Automatic total stations

possibility of taking arcs in area computation.
This type is most common total station used now-a-days.
4 Graphical view of plots and land for qick visualization.
They sense both the horizontal and vertical angles

ed
5 Coding to do automated mapping. As soon as the field electronically and measure the slope distances, compute
jobs are finished, the map of the area with dimensions the horizontal and vertical components of those distances,
bl I
pu M
is ready after data transfer. and determine the coordinates of observed points, it is

ish
6 Enormous plotting and area computation at any user. necessary to properly orient the instrument of some known
Re NI

directions such as true north, magnetic north or to some

7 Integration of database (exporting map to GlS packages) known bearing. The coordinate information obtained can
be @

8 Automation of old maps. either be stored in the total station’s memory or by using
an external data collector.
9 Full GIS creation (using map info software)
o ht

10 Local language support Manual total stations and semi-automatic total stations
are obsolete now. At present, it is the age of fully automatic
t t rig

Disadvantage of total station total stations and robotic total stations.

No py

1 Their use does not provide hard copies of field nots. Almost all total stations in the market use infrared as the
Hence it may be difficult for the surveyor to look over carrier for distance measurement. The less expensive unit
Co

and check the work while surveying. with a single prism reflector can measure distances up to
1000 m. Those in higher price range are capable of
2 For an overall check of the survey, it will be necessary measuring distances up to 2000 m, when single prism is
to return to the office and prepare the drawings using used. the accuracies of measurements witn the less
appropriate software. expensive instruments probably run about 6 ( 5 mm/ 5
3 They should not be used for observations of the sun, ppm) and the expensive total stations can run about 6 ( 1
unless special filters, such as the Troelof’s prism, are mm/ 1 ppm.)
used. If not, the EDM part of the instrument will be
damaged. Principle of EDM

4 The instrument is costly, and for conducting surveys Measurement of distance is accomplished with a
using totals station, skilled personnel are required. modulated microwave of infrared carrier signal, generated
by a small solid-state emitter within the instruments optical
Types of total staions path, and reflected by a prism reflector or the objected
under survey. the modulation pattern in the returning signal
In the early days, three classes of total stations were is read and interpreted by the onboard computer in the
available - manual, semi-automatic and automatic. total station. The distance is determined by emitting and
receiving multiple frequencies, and determining the integer
Manual total stations number of wavelengths to the target for each frequency.
Most total stations use purpose-built glass Porro prism
It was necessary to read the horizontal and vertical angles
reflectors for the EDM signal, and can measure distances
manually in this type of instrument. The only value that
to a few kilometers. The typical total station can measure
could be read elevtronically was the slope distances.
istances to about 3 millimeters or 1/1000th of a foot..
185
 From the above figure

• Where E & N gives the position and Z gives the reduced

level
• Suppose we know ( x,y,z )
• We need an algorithm to calculate positions of x1,
y1,z1) ; (x2, y2, z2) & ( x3, y3, z3) w.r.t. (x,y,z).
• For this algorithm we need inputs.

Inputs for the algorithm are

ed
• Co-ordinates at which the instruments stands.

bl I
pu M
• Height of the instrument

ish • Orientation of the instrument (Hz = 0).

Re NI

• Height of the reflector

Basics of total station
be @

• Angle at which the prism is placed w.r.t. orientation.

• Angles and distances are measured from the total • or
o ht

station to points under survey, and the coordinates (

• 00° 00’ 00”
X,Y, and Z or nothing, easting and elevation) of surveyed
t t rig

points relative to the total station position are calculated • D° M’ S”

using trigonometry and triangulation. • Hi
No py

• Most modern total station instruments measure angles

by means of electro-optical scanning of extremely
Co

precise digital bar-codes etched on totaling glass

cylinders or discs withing withing the instrument. The
best quality total stations are capable of measuring
angles to 0.5 arc-second. Inexpensive “construction
grade’ total stations can generally measure angles to
5 or 10 arc- seconds.
• Total Station - requires lines line of sight obsrvations
and must be set up over a known point or with line of
sight 2 or more points with known location.

186 Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.177
Construction Related Theory for Exercise 4.6.178
Draughtsman Civil - Total station

Measurement with total station

Objectives : At the end of this lesson you shall be able to
• explain the equipment required for total station surveying
• explain the procedure of measurement with total station.

For using the modern electronic survey equipments, 5 Survey tools

surveyors are need to be more maintenance conscious
than they were in the past. They must have to thorough a Stakes, nails, paint, marker
knowledge, about power sources, downloading data and
b Hammer
the integrity of data.
c Thermoeter, barometer / altimerer
For the survey of an area, the survey crew (two person
d A pair of radio (with hands- free head set)
crew, consisting of a party chief / rod person and a note
keeper / instrument person) need the following equipment e Clipboard, field note, pen
inventory.
f Compass
1 Total station set
Setup
a Total station instrument in a hard case
The following steps followed for the setup pf a total station,

ed
b Battery charger at a station point.

bl I
pu M
c Extra batteries
d Memory module / card, serial cable
ish 1 Choose an adequate instrument station. Make sure
that an observer can safely operate the instrument
Re NI

without knocking it over. It is necessary to have the

e Rain cover
center of the instrument, which is the point of
be @

f User manuals interscetion of the transverse axis of the instrument,

directly over a given point on the ground (the instrument
g Tripod
station).
o ht

h Tape measure
2 Remove the plastic cap from the tripod, and leave the
t t rig

2 Prism set instrument in the case until the tripod is nearly level,
Stretch the tripod legs 10 - 15 cm shorter than their
No py

a Prism maximum length.

b Prism holder 3 Open the legs of the tripod to set the tripod head at the
Co

level of the operator,s upper chest. When the total

c Centering rod station is set up on the head, the operator’s eye should
be slightly above the eyepiece. The instrument height
3 Back sight set is important for an effective and comfortable survey. It
differs in the looking down position and the looking up
a P rism position. One should not touch or cling to the tripod
b Prism holder during the survey.
c Prism carrier ( to be fixed to tribrach, with optical / 4 At a new station without a reference point on the ground,
laser plummet) level up the total station at an arbitrary point, where a
stake can easily go in and be stetady, and put down
d Tribrach ( to exchange prism carrier and total station) the stake at the centre using the plummet.
4 Data Processing 5 To occupy an existing station above a refrence point,
first roughly level up the tripod head right above the
a Laptop computer with serial port or USB port point. For levelling up, a small level is useful to find out
the position, use a plumb bob or drop a stone through
b Serial cable or USB-serial adaptor
the hole in the tripod head.
c Terminal application
6 Once roughly levelled and centered, push each tip of
d Application programme: MS Excel, Adobe llustrator, the tripod leg firmly into the ground, applying full weight
Co-ordinate Converter, etc. of the observer on the step above the tip. Apply the
weight along the tripod leg without bending it.
e Data backup device media (Zip, meaory card, etc.)

187
7 Check the level and center it again. Adjust the level by 10 Pull out the optical plummet and use the optic ring to
changing the leg length. focus at the graticule and then focus at the mark on
the ground. Turn on the laser plummet. Rotate the
8 Fix a tribrach with a plummet, a tribrach and a prism
plummet or the total station to check it is centered
carrier with a plummet or a total station with a built-in
within 1cm from the reference point. If not, estimate
plummet on the tripod head.
the amount of offseet and carefully translate the entire
9 Adjust the three screws of the tribrach to center the tripod as much as offset.Return to 4 and try to level
bubble of a spirit level with the following steps: and center, therefore, rough centering within 1 cm is
necessary. Be careful to see that the center of the
a Release the lock of the horizontal circle. Rotate
optical plummet or the laset point is on an axis
the instrument to the plate level parallel to AB at
perpendicular to the horizontal circle of the total station.
the 1st position.
If the total station is not level, the plummet line does
b Turn the foot screws A and B in the opposite not coincide with the plumb line.
direction, the same amount to center the plate level.
11 Put the total station on the tribrach if it is not there.
This will adjust the tilt on the aa’ axis.
12 Use the plate level for the final levelling of the total
c Rotate the instrument 90° to set the plate level, at
station. Follow the instructions given in Fig 1
the 2nd position.
13 When the total station is finely levelled up, use the
d Turn the foot screw C to the centre plate level,
plummet to check centering. If the plummet center is
adjusting the tilt along cc’.
off the reference point, slightly loosen the fixing screw
e Rotate the instrument 90° to set the plate level in below the tripod head and translate the tribrach to place
the 3rd position. the plummet center on the exact point. Do not rotate.
f Turn the foot screws A and B in the opposite When the translation is done, tighten the fixing screw
moderately. If any portion of the base of the tribrach

ed
direction, the same amount to eliminate half the
centering error. goes outside the tripod head, return to 4.
bl I
pu M
ish
g Rotate the instrument 90° to set the plate level at 14 Rotate the total station by 180°. If the plummet center
the 4th position. goes away from the point, slightly loosen the fixing
Re NI

screw and slide the total station halfway to the center.

h Turn the foot screw C to eliminate half the centreing
error. 15 Repeat the setps 12 and 13 until the plummet center
be @

stays exactly on the center of the mark.

i Repeat b to h until the plate level is centered in all
16 Tightem the fixing screw firmly without applying too
o ht

directions ( give a little time for slow movement of

the bubble in viscous fluid). much pressure. Never loosen the screw until all the
measurements are finished.
t t rig

17 Measure the instrument height. The centre of the total

No py

station is marked on the side of the alidade. The vertical

distance between the mark and the ground is the
instrument height.
Co

18 Check the plate level from time to time during the

measurement before the total station tilts beyond the
automatic correction.

Setting up a back sight

A back sight is a reference point for the horizontal angle.

At the beginning of a new survey, a back sight con be set
at and arbitrary point and marked. The best way to set up
a back sight is to use a prism carrier and tribrach on a
triped. the procedure for levelling up and centering of the
prism is the same as that for the total station. If there is
not plummet in the trubrach and the prism carrier, use the
plummet of the total station and then exchange the total
station above the tribrach with a prism carrier. A prism
should be put right on the reference point when sighting is
possible from the total station.

188 Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.178
Measure the target height at the back sight. This height is 4 Adjust the telescope to best fit to the observer’s eye.
the vertical distance between the centre of the target (prism) Using the inner ring of the eyepiece, make the image
and the ground beneath. When the station and back sight of the cross-hair sharp and clear.
are ready, measure the azimuth from the station to the
5 Rotate the alidade until the Hz angle reading is equal
back sight using a compass. The azimuth is between 0°
to the azimuth to the back sight measured by the
and 360° measured clockwise from north. Correct the
compass (for Sokkia models only). Push the HOLD
magnetic declination to get the tru azimuth and record the
key once. The Hz angle will not change until thenext
true azimuth. If the geographic coordinate or grid
hold.
coordinates of the point occupied by the total station and
the target at the back sight is known, then the total station 6 Aim at the very center of the prism at the back sight.
will automatically calculate the true azimuth, provided the For the coarse aiming, rotate the alidate and the
station values are fed into the total station manually. telescope by hand using optical sight. Adjust focus
using the outer ring of the eyepiece. When the prism
Measuremet with total station comes into the sight and clos to the cener, lock the
horizontal and vertical drives. Then use dials to aim at
When both the total station and back sight are finely the exact center of the prism.
levelled and centered, thehardware setup is over and the
7 For Sokkia models, push HOLD button again. The
software setup is to be started. The software setup of a
horizontal reading will now change according to the
total station differs from one make to another. One has to
rotation of the telescope in the horizontal direction. For
follow the user’s manual of each instrument. The list below
leica models, input the azimuth of the back sight
gives common important settings for most instruments,
manually in the measurment setup window.
Most total stations memorize these settings, but it is better
to check through the setup menu in order to avoid a false 8 If a station ID and back sight ID are requirred, use a 2-
setting. digit or 3-digit serial number like 101, 102,.......for each

ed
reference point. Use a 4-digit number for unknown
System : Choose appropriate existing interface for data points.
bl I
pu M
output.

ish 9 Input station parameters like hi (height of the

Re NI
instrument), E0, N0, and H0 (easting, northing and RL
Angle measurements : Tilt correction / tilt compensator
of the point where the instrument is setup). Use 1000,
(2 axis)
1000 and 1000 for E0, N0 and H0 to avoid negative
be @

Horizontal angle increments : At right angles figures. If the coordinates are known, manually input
(Clockwise). the data.
o ht

10 Input the traget height (hr.)

Unit setting : Angle in degrees / min. / sec., distance in
t t rig

meters, temperature in °C and pressure in hPa. 11 Check the pointing at the prism again.
12 Using the distance calculation key. make the back sight
No py

EDM settings : Select IR laser, fine measuring mode, use measurement. From the LCD display of the total
RL with caution. So appropriate value for the prism station, not the horizontal angle, the vertical angle,
Co

constant (from the user’s manual of the equipment). slope distance, easting, northing and height, and record
them in a field book with a sketch of the plan. Here the
Atmospheric parameters : Get ppm for the diagram from horizontal angle, vertical angle and the slope distance
the manual of the equipment or let the total station calculate are the raw data.
from hPa and degree centrigrade.
13 Create a new job or open an existing job. A job is a
Commnunications : Set all parameters the same for a block of data sets stored in the memory like a file. One
total station and data logger / PC. They are rate. data can creat a new job or append data to an existing job.
bits, parity, end mark and stop bits. Refer the manual for A job name is used as an output file name in a new
each device. Lecia total station with. gsi extension

Total station initial setting (General setting required Precautions to be taken while using a total station
for all models)
The following precautions need to be taken while using a
The following are the steps for the initial setting of a total total statio:
station:
1 Always carry a total station in a locked hard case even
1 Turn of the total station. for a very short distance. Take the total station out of
the hard case only for fixing it firmly on a tripod for
2 Release both horizontal and vertical locks. taking observations.
3 Some total stations require rotating the telescope 2 Do not move or carry a tripod with the total station
through 360° along the vertical and horizontal circles fixed on it. except for centering.
to initalize angles.
Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.178 189
3 Use both bands to hold the total station handle. 6 Always keep the top of the tripod, the bottom and top
of the tribrach and the bottom of the station clean and
4 Never release the handle before the total station is fixed
away from any shock and impact.
with the tripod’s fixing screw.
7 Take maximum carre when the tribrach is removed from
5 Set up the tripod as stable as possible.
the total station.
8 Do not make the total station wet.

ed
bl I
pu M
ish
Re NI
be @
o ht
t t rig
No py
Co

190 Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.178
Construction Related Theory for Exercise 4.6.179
Draughtsman Civil - Total station

Cheracterstic and features of total station

Objectives : At the end of this lesson you shall be able to
• define features of total station
• state the characterstics of total station
• advantages and dis advantages of total station.

FEATURES OF TOTAL STATIONS For those construction projects where long distances are
required to be measured, GPS methods are used in
Total station are capable of measuring angles and distances preferance to total stations. There is no standard difference
simultaneously and combine an electronic theodolite with at which the change from one to the other occurs, as this
a distance measuring system and a microprocessor. will depend on a number of factors, including the accuracy
required and the site topography.
ANGLE MEASUREMENT
Rapid measurement reduces the measurement time to a
All the components of the electronic theodolite described prism to between 0.5 and 1’s for both phase shift and
in the previous lectures are found total stations. pulsed systems, but the accuracy for both may degrade
slightly.
The axis configuration is identical and comprises the vertical
axis, the tilting axis and line of sight (or collimation). The Tracking measurements are take extensively when setting
other components include the tribatch with levelling out or for machine control, since readings are updated

ed
footscrews, the keyboard with display and the telescope very quickly and vary in response to movements of the
bl I
pu M
which is mounted on the standards and which rotates prism which is usually pole-mounted. In this mode, the
around the tilting axis.
ish distance measurement is repeated automatically at
Re NI

intervals of less than 0.5s.

Levelling is carried out in the same way as for a theodolite
by adjusting to centralise a plate level or electronic bubble. For reflector less measurements taken with a phase shifr
be @

The telescope can be transited and used in the face left sysrem, the range that can be obtained is about 100m,
(or face I ) and face right ( or face II ) positions. Horizontal with a similar accuracy to that ontained when using a
o ht

rotation of the total station about the vertical axis is prism or foil.
controlled by a horizontal clamp and tangent screw and
t t rig

rotation of the telescope about the tilting axis. Characterstics of total station
No py

The total station is used to measure angles in the same 1 Angle units degree or gon
way as the electronic theodolite.
2 Distance units ft or m
Co

Distance measurement 3 Pressure unit mHg or mmHg

4 Temperature units â °F or â °C
All total station will measure a slope distance which the
onboard computer uses, together with the zenith angle 5 Prism constant -30 or -40mm
recorded by the line of sight to calculate the horizontal
6 Offset distances
distance.
7 Face 1 or Face 2 selection
For distances taken to a prism or reflecting foil, the most
8 Height of instrument (HI)
accurate is precise measurement.
9 Height of reflector (HR)
For phase shift system, a typical specification for this is a
10 Automatic point number incrementation
measurement time of about 1-2s, an accuracy of (2mm +
2ppm) and a range of 11 Point numbers and code numbers for occupied and
sighted stations
3-5km to a single prism.
12 Date and time settings
Although all manufacturers quote ranges of several
Capabiltites of a Total Station
kilometres to a single prism.
• Monitors battery status, signal attenuation, horizontal
and axes status, collimation factors
• computes coordinates

191
• Traverse closure and adjustment • Without these observation in the recorded data, the
orientation of the data will always be in question.
• Topography reductions
• The use of a total station with a data collection can be
• Remote object elevation
looked upon as two separate and distinct operations.
• Distance between remote points
Following is the typical procedure for data collection
• Inversing
in total station
• Resections
• Set up and level instrument
• Horizontal and vertical collimation corrections
• Turn on total station
• Setting out
• Create a file or open existing file
• Vertical circle indexing
• Record Occupied station Name and instrument height
• Records, search and review
• Set Coordinate for Occupied Station
• On-board software
• Set backsight name and reflector height and observe
• Traansfer of data to the computer
the coordinate of the backsight (known) station and
• Transfer of computer files to date recorder record the data

Field procedures for Total Station in topographic • Give name for foresight station and set reflector heinght
surveying • Measure the foresight station and record the data

• A set routine should be established for a survey crew • For detailing, set detail point name and reflector height
to follow and start recording the data of different location.

ed
• After completion of recording the data, Power off the
•
bl I
Standard operating procedure should require that control
pu M
machine and transfer the instrument to next station

ish
points be measured and noted immediately on the data
collector and/or in the field book after the instrument
and procedure as above.
Re NI

has been set up and leveled

Total station consists of an electronic theodolite, an
• This ensures that the observation to controlling points electronic distance measuring device (EDM) and a micro
be @

are established before any outside influences have had processor having a memory unit. By using this instrument
an opportunity to degrade the setup it is possible to find out the coordinates of a reflector
o ht

• In making observations for an extended period of time adjusting the cross hair of the instrument and at the same
at a particular instrument location, reonserve the control time measuring the vertical angles, and slope distances.
t t rig

points from time to time A micro processor deals with the recording, readings, and
the fundamental calculation of measurements.
No py

• This ensures that any data observed between the

control shot are good or that a problem has developed The major advantages and disadvantages of total station
Co

and appropriate action can be taken to remedy the are as following:

situation
ADVANTAGES OF TOTAL STATION:
• As a minimum, require servey crews to observe both
vertical and horizontal control points at the beginning
1 Quick setup of the instrument on the tripod by utilizing
of each instrument setup and again before the
the laser plummet.
instrinstrument is picked up
2 Programmed with on board area computation for
• One of the major advantages of using a total station
computing the area of a field.
equipped with data collection is that some errors
previously attributed to blunder can be minimized or 3 It supports local languages.
eliminated.
4 It shows the graphical view of land and plots.
• Even if the wrong reading is set on the horizontal circle
5 No recording and writing errors.
on the field or the wrong elevation is used for the bench,
the data itself may be precise 6 It gives more accurate measurements than other
conventional surveying instruments.
• To make the data accurate, many software packages
will allow the data to be rotated and/or adjusted as it is 7 Data can be saved and transferred to a PC.
processed. 8 It has integrated database.
• The only way to assure that these corrections and/or 9 Computerization of old maps.
observations have been accurately processed is to
compare the data to control points

192 Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.179
10 All in one and multitasking instrument, from surveying 2 It might be troublesome for the surveyor to investigate
to GIS creation by using the appropriate software and check the work when surveying.
11 Faster work, saves time, quick finishing off the job. 3 Working with total station is not so easy, as more
skilled surveyors are required to conduct a total station
DISADVANTAGES OF TOTAL STATION: survey.
4 To check the survey work thoroughly it would be
1 The instrument is costlier than other conventional
necessary to come back to the office and prepare the
surveying instruments.
drawings by usning the right software.

ed
bl I
pu M
ish
Re NI
be @
o ht
t t rig
No py
Co

Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.179 193
Construction Related Theory for Exercise 4.6.180
Draughtsman Civil - Total station

Principle of EDM - Working need setting and measurement

Objectives : At the end of this lesson you shall be able to
• defene EDM
• state the prenciple of EDM
• features of EDM.

What is EDM ?

EDM is the electronic distance measuring device,

measures from the instrument to its target. EEDM sends
out laser or inframed beam which is roflected back the
unit and the unit used velocity measurements to calculate
the distance traveled by the beam.

ed
bl I
pu M
ish
Re NI
be @
o ht
t t rig
No py
Co

194
History
3

Theeodolite & Tape

Stadia
EDM & Theodolite
EDM, Theodolite & Data Collector

Prior to the total station, Theodolite with EDMs and data

collectors were used to record number of points, and for
measuring long distances. The systems were heavy, prone
to failure, and many times the parts incompatible.

Prior to these systems, optical (stadia) and manual (tape)

systems were used to measure distances.

ed
bl I
pu M
ish
Re NI
be @
o ht

History

• First introduced in the late 1950’s

t t rig

• At first they were complicated, large, heavy and suited

primarily for long distances
No py

• Current EDM’s use either infrared (light waves) or Principles of EDM

Co

microwaves (radio waves)

Gereral principles of EDM
• Microwaves require transmitters/receivers at both ends
• Infrared use a transmitter at one end and a reflecting Electromagnetic energy
prism at the other and are generally used more
frequently. Travels based on following relation

EDM Properties v
v = f λ so λ = v = c/n
• They come in long (10-20 km), medium (3-10 km), and f
short range (.5-3 km). Range limits up to 50 km
Instensity modulate EM energy to specfic frequency
• They are typically mounted on top of a theodolite, but
can be mounted directly to a tribrach.
Principles of EDM
Total station
ADVANTAGE OF USING EDM
=
1 Precise measurement of distance
Theodolite with built in EDM
2 Capabale of measuring long distances
±
3 Relectroless are single person operation
Microprocessor

Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.180 195
ElECTRONIC DISTANCE MEASUREMENT (EDM) peg
traverse
DISADVANTAGE OF USING EDM
procedure
1 Electronic = batterers
Full transcript
2 Accuracy affected by atmospheric conditions.
Things to remember in total station
3 Can be expensive
• A total station is an electronic optical instrument widely
USE OF EDM
used in modern surveying
(a) measuring distance • Total station instrument combine three basic
components
(b) setting distance
• An EDM instrument, and electronic digital theodolite
Different Wavelength Bands Used By EDM and a computer or microprocessor into one integral
unit
Usally, EDM uses three different wavelength bands and
their characteristics are: • They digitally observe and record horizontal directions,
vertical directions and slope distances
Microwave Systems • These digital data observations can be adjusted and
transformed to local X,Y, and Z coordinates using an
Range up to 150 km internal or external microprocesor.

Wavelength 3 cm • Various atmosphere corrections, grid and geodetic

correctoins, amd elevation factors can be input and

ed
Not limited to line of sight applied
bl I
pu M
Unaffected by visibility
ish • The total stations may internally perform and save the
observation or these data may be download to
Re NI

anexternal data storage

Light Wave Systems
• Angles can be electronically encoded to one are-second
be @

Range up to 5 km (for small machines) with a precision down to 0.5 arc-second

• Digital readouts eliminate the uncertainty associated
o ht

Visible light, lasers

with reading and interpolating scale and micrometer
t t rig

data
Distance reduced by visibility
• The electronic angles - measurement system
No py

Infrared Systems minimizes some of the horizontal and vertical angle

errors that normally occur in conventional
Co

Range up to 3 km
• The modern versions of survey total station called robotic
total station, let user control the instrument from a
Limited to line of sight
distance with the help of remote control.
Limited by rain, fog, other airbore particles • These instruments are also equipped with dual - axis
compensator, which automatically correct both
Total station : horizontal and vertical angles for any deviation in the
plumb line.
tripod
theodolite
hammer
plumbob

196 Construction: Draughtsman Civil (NSQF Level-5) - R.T. for Exercise 4.6.180