1. ADVANCED
SURVEYING
EQUIPMENTS

2. MODERN EQUIPMENTS
• Total Station
• Electronic Distance Measuring (EDM)
• Electronic Theodolites
• Digital Levels

3. TOTAL
STATION

4. Introduction
Total Station is a lightweight, compact and fully integrated
electronic instrument combining the capability of an EDM
and an angular measuring instrument such as theodolite.
Total Station can perform the following functions:
• Distance measurement
• Angular measurement
• Data processing
• Digital display of point details
• Storing data is an electronic field book
• Setting Out Points
• Tracking
• Staking Out
Fig. Total Station

5. Parts
of
total
station

6. Important features of total station:
• Keyboard control – All Functions are controlled by operating Keyboard.
• Digital panel – The Panel displays the values of distance, angle, height and the
coordinates of the observed point.
• Remote height object – The heights of some inaccessible objects such as towers
can be read directly. The correction for earth’s curvature and mean refraction,
are done automatically by The Microprocessor.
• Traversing program – The Coordinates of the Reflector and the angle or bearing
on the reflector can be stored and can be recalled for next set up of instrument.
• Setting out for distance direction and height -While locating the point (by
entering points in instrument) on the ground using a target, then the instrument
displays the angle through which the theodolite has to be turned and the
distance by which the reflector should move.

7. • Dual axis compensation : The dual axis tilt sensor monitors any inclination of
the standing axis in both X- and Y-directions. These tilt sensors generally have
range of 3'. Consequently horizontal and vertical angle readings are free from
error due to any deviation of the standing axis from the perpendicular. Thus
permitting single-face observations without loss of accuracy.
Fig. Principle of dual axis compensator

8. • Levelling and centering: A few TS have electronic display for levelling operation
enabling rapid and precise leveling. The electronic levelling also eliminates errors
caused by direct sunlight on plate bubbles. Using a Laser plummet, visible laser
dot is projected on to the ground that helps in quick and convenient centering of
the instrument.
• Storage: Most TS have on-board storage of records using PCMCIA memory cards
of different capacity. The card memory unit can be connected to any external
computer or to a special card reader for data transfer. The observations can also
be downloaded directly into intelligent electronic data loggers.
• Remote control systems: This allows truly one-person surveying capability. It is
particularly useful for mass point surveys, cadastral surveys, staking out and
machine guidance. Control of operation is transferred to the surveyor at the
survey point where all functions can be called up. The unit generally employs a
radio communication between TS and the prism. The control unit, battery,
antenna and radio modem are integrated to allow full control over instrument
and its operation.

9. Fig. Laser Plummet in TS
Fig. Remote COntrol System in TS

11. • Measurement modes: Variety of measurement modes are available with TS such
as precise, accurate, and fast tracking, etc. Depending up on accuracy levels
required and measurement times, the surveyor can choose an appropriate
measurement mode.
• Automatic target recognition (ATR): This facility ensures that the instrument will
lock on to the active target (by using RMT: remote measurement target). The
instrument receives coded signal by IR diode on the RMT. In this mode, the
instrument automatically follows the reflector after the first measurement. The
telescope is pointed in the general direction of the target, and the ATR module
completes the fine pointing with excellent precision and minimum measuring
time as there is no need to focus. It can also be used on a moving reflector. A
single key touch records all data without interrupting the tracking process. Omni-
direction (360o) prisms reflector are used for short distances which are always
aligned automatically ensuring high accuracy (Figure 3.7). For longer distances
directional active targets are available. The ATR mode also allows operation in
darkness.

12. • Guide light or Lumi-guide tracking light : This arrangement is fitted above the
telescope objective lens and enables the target operator to maintain alignment
when setting-out points.
This system emits two visible beams of coherent red light, one steady and one
blinking, enabling the rodman to locate the correct line quickly and easily by
finding the position where both are visible. This light changes colour when the
operator moves off-line.
It can also be used as a convenient signal to the rodman, assists in one-man
clearing of lines and work as a prism illuminator in night surveying.

13. • Reflectorless or direct reflex measurement: Distance measurement without
prism is also available on many instruments, typically using two different coaxial
red laser systems. One laser is invisible and is used to measure long distances (6
km to a single reflector), the other is visible, does not require a reflector, and
has a limited range of about 200 m. The reflectorless measurements are useful
for surveying the facades of buildings, tunnel profiling, cooling tower profiling,
bridge components, and dam faces - indeed any situation which is difficult or
impossible to access directly.
Fig. Reflectorless Measurement

14. Advantages of using total station:
• Field work is carried out very fast.
• Accuracy of measurement is high.
• Manual errors involved in reading and recording are eliminated.
• Calculation of coordinates is very fast and accurate. Even corrections for temperature
and pressure are automatically made.
• Computers can be employed for map making and plotting contour and cross-sections.
Contour intervals and scales can be changed in no time.
Disadvantages of using total station:
• Their usage doesn’t offer hard copies of field notes. Hence, it could be difficult for the
surveyor to look over and assess the work whilst surveying.
• For a general check of this survey, it is going to be necessary to come back to the
office and prepare the drawings utilizing appropriate software.
• They shouldn’t be used for observations of the sun, unless special filters, like the
Troelof’s prism, are utilized. Otherwise, the EDM part of this instrument will be
damaged.
• The instrument is costly, and also for conducting surveys with a total station, skilled
personnel is necessary.

15. Types of total stations :
• Mechanical/manual TS: The conventional multipurpose manual TS are used for
routine works with powerful built-in applications program and are cheaper
than the other types TS.
• Motorized TS: The motorized TS are equipped with servo to allow for fast,
smooth and accurate aiming. The servo technology enables automated
measurement. For example, during angle measurement one can simply aim the
instrument at each point. The instrument can then repeat the measurements
automatically as may times as required. Servo equipped TS act as base for
autolock and robotic surveying.

16. • Autolock TS: Autolock TS allow for a semi-automatic measurement where
measuring and recoding takes place at the TS. In this case the instrument
searches for an active remote positioning target (RMT), locks to it and follows
the target as it moves to different points. Autolock technology eliminates the
need for time-consuming error prone focusing and allows you to work
effectively even in poor and low visibility environment. It improves the time
efficiency by up to 50%.
• Automatic/Robotic TS: This a true one person surveying TS and is ideal for
surveying and stakeout operations. In this TS, the control unit can be taken to
the prism to record measurements and collect other data. Generally a radio
communication is used between TS and the prism. The control unit, battery,
antenna and radio modem are integrated to allow full control over instrument
and its operation. The prism used may be omni-directional (usually for short
distance up to 500 m) which is always aligned to the instrument or directional
for longer distances. During stakeout, the control unit is used to move to point
of interest. It improves the time efficiency by up to 80%.

17. Motorized TS AutoLock TS Automatic TS

18. Servo Driven Total Station
• Servo-driven instruments are particularly appealing where automatic pointing is desired.
• This is done by using motors to aim and position the instrument.
• In the case of setting out, it makes it feasible to set control points for surveying with very
little sighting through the telescope.
• For data collection, the pre-determined coordinates of the point (observation from the
backsight Readings after instrument setup), are used to automatically set the horizontal and
vertical angles of the instrument.
• During traversing the servo drives can be used to point the instrument in the direction of the
next target of the observing program, requiring only fine pointing adjustments by hand.
• When these instruments are used manually, because they are servo-driven, they have
friction clutches that afford great speed in point, as there are no locks to be adjusted.
• The servo-driven instrument has the disadvantage of data collection and coding occurring at
the instrument.

19. Prism Poles of Total Station
• For most programs, a Retro Reflector Prism is attached to the top
of the prism pole such that there isn’t any eccentric offset
correction demanded. Otherwise, then the retro-reflector offset
correction has to be determined and implemented to found
spaces.
• Utilization of a fixed height pole helps reduces HR blunders.
• A shoe to the pole point could is required in soft ground. A normal
rod level is utilized to interrogate the prism pole above a point.
• Many poles have built-in rod levels to ease plumbing the prism.
Fig. Prism Pole

21. Application Software "Menu Tree"
MAIN MENU
1. Job Manager 5. Congo
2. Station Setup 6.Communications
3.Collection 7.Systems
4. Stakeout
FNC KEY
1.Switches 5.Settings
2. View/Edit 6.Status
3.Total Stn 7.Check Level
4.Notes
STATION SETUP
1. Known Station
2. Resection
3. Backsight Check
COGO
1. Inverse
2. Azim & Disk
COMMUNICATIONS
1. Upload
2. Download
3. Upload Options
4. Dnload Options
5. Comm Settings
SYSTEMS
1. Settings
2. Calibration
3. Copy Card
4. Format Card

22. ELECTRONIC
THEODOLITE

23. Electronic
Theodolite
• Theodolites or transits are used to measure
horizontal angles. These have evolved as follows:
1. Vernier theodolite (open face and Vernier
equipped instruments)
2. Optical theodolite (enclosed with optical readouts
with direct digital readouts or micrometer
equipped readouts)
3. Electronic theodolites (enclosed with electronic
readouts)
• Electronic theodolites operate like any optical
theodolite with one major difference that these
instruments have only one motion (upper) and
hence have only one horizontal clamp and slow
motion screws.

24. Typical specifications for digital theodolites are
generally given as follows:
• Magnification: 26X to 30X
• Field of view (FOV):1.50.
• Shortest viewing distance: 1.0 m
• Angle readouts: direct 5" to 20"
• Level sensitivity: plate level vial 40"/2 mm,
circular level vial 10"/2 mm

25. Characteristics of electronic theodolites
• Angle least count can be 1" with precision ranging from 0.5" to 20"
• Digital readouts eliminate the personal error associated with reading and
interpolation of scale and micrometer settings.
• Display window/unit for horizontal and vertical angles available at either one or
both ends.
• Some digital theodolites have modular arrangement where they can be upgraded
to be a total station or have an EDMI attached for distance measurements.

26. Electronic
Distance
Measurement

27. Introduction
Measurement of distance is accomplished with a modulated microwave or
infrared carrier signal, generated by a small solid-state emitter within the
instrument's optical path, and bounced off of the object to be measured. The
modulation pattern in the returning signal is read and interpreted by the
onboard computer in the EDM. The distance is determined by emitting and
receiving multiple frequencies, and determining the integer number of
wavelengths to the target for each frequency.
Emitter Reflector
Transmitted Beam
Reflected Beam

28. History of EDM
• Development of EDM technology started during World War II with the
development of RADAR (Radio Detection and Ranging). Radars returned
the distance to an object (and later versions the speed of the object through
the Doppler shift) by timing the length of time the from the transmission of a
pulse to its return.
• Electronic distance measurement can be done by instruments like geodimeter,
tellurometer or distomat etc.
• The first EDM instrument called Geodimeter was developed in Sweden in the
year 1948. They were complicated, large, heavy, and suited primarily for long
distancesGeodimeter is geodetic distance meter developed based on a
modulated light beam.
• The second instrument for EDM was designed and developed in Africa in the
year 1957, named Tellurometer. This instrument employs modulated
microwaves.

29. • As years passed technology has improved drastically. At present, we
have modern EDMs that displays distance in digital form and many gains
microcomputers that calculates horizontal and vertical distance i.e. DX and DY.
They also show sloped distance (DH) using either infrared (light waves) or
microwaves (radio waves).
• Distance range was about 10km during daylight and 25km at night. Greater
range during daytime was achieved by using radio waves. Distances up to 50
km could be measured in daylight with this instrument and later models.

30. Fig. First Geodimeter
Fig. Modern Geodimeter

32. 1. Microwave Instruments
• These instruments make use of microwaves. Such instruments were invented as early as 1950 in
South Africa by Dr. T.L. Wadley and named them as Tellurometers. The instrument needs only 12 to
24 V batteries. Hence they are light and highly portable. Tellurometers can be used in day as well as
in night.
• The range of these instruments is up to 100 km. It consists of two identical units. One unit is used as
master unit and the other as remote unit. Just by pressing a button, a master unit can be converted
into a remote unit and a remote unit into a master unit. It needs two skilled persons to operate. A
speech facility is provided to each operator to interact during measurements.
2. Infrared Wave Instruments
• In this instrument amplitude modulated infrared waves are used. Prism reflectors are used at the
end of line to be measured. These instruments are light and economical and can be mounted on
theodolite. With these instruments accuracy achieved is ± 10 mm. The range of these instruments is
up to 3 km.
• These instruments are useful for most of the civil engineering works. These instruments are available
in the trade names DISTOMAT DI 1000 and DISTOMAT DI 55.
3. Visible Light Wave Instruments
• These instruments rely on propagation of modulated light waves. This type of instrument was first
developed in Sweden and was named as Geodimeter. During night its range is up to 2.5 km while in
day its range is up to 3 km. Accuracy of these instruments varies from 0.5 mm to 5 mm/km distance.
These instruments are also very useful for civil engineering projects
Types of EDM Instruments on basis of Frequencies:

33. Fig. Generalized block diagram illustrating
operation of electro-optical EDM instrument
Major components constitututing a typical
EDMI
1. Carrier signal
2. Modulation signals and modulator
3. Signal transmitter and signal receiver
4. Beam splitter
5. Reflector
6. Filter
7. Amplifier
8. Phase Discriminator
9. Display Unit

34. Carrier Signal: This this the guiding factor for many of the characteristics of EDMI that
follow. The following descriptions follows from Burnside (1971). Three very distinct types
of frequencies are used giving rise to three groups of instruments.
a) Long radio waves of the hundreds of meters
b) Micro radio waves of the order of a few centimeters
c) Wavelength near the visible spectrum of the order of micrometers
Modulator and modulation signals Modulation is defined as the process of varying the a
amplitude (amplitude modulation), frequeny (frequency modulation), phase (phase
modulation) or the polarization (polarization modulation) of a carrier wave in
accordance with other signals.
The long wave instruments are unmodulated and the carrier signal itself is the
measurement signal.
For microwave instruments, the carrier signal is generated by a reflex Klystron which is
more suitable for frequency modulation. Two main reasons for modulation with
microwave instruments are:
• Since these use short wavelength (10 or 3 cm), there would be some ambiguities in
resolving the integer m at long working ranges.
• At long distances it is doubtful whether the phase of the signal would be stable at the
end of long path through the atmosphere. The modulation signal is, therefore, of much
longer wavelength than the carrier.

35. • Signal transmitter and receiver: For long waves the most efficient radiator
is a straight vertical wire of effective length λ /4 operating as one half of a
dipole. In case of microwave, the signals can be radiated by dipoles of the
appropriate dimensions. These approximate to point sources of radiation
and are located at the focus of the sheet metal parabolic reflector, which
produces a well directed beam. For visible spectrum wavelength, high
degree of collimation is achieved making use of optical lens system.
• Beam splitter: It divides the light emitted from the diode into two signals:
an external measurement beam and an internal reference beam. By means
of telescope mounted on EDMI, the external beam is targeted to a retro-
reflector (explained later).

36. • Reflector Reflectors are required to return the signal to the point of comparison (at
the master station) and have different requirements for different types of EDMIs as
given below:
Long wave instruments: In these signals received and amplified at the remote station
are retransmitted - though not at the same frequency but one related to it. Thus
generally two separate aerials may be required.
Microwave instruments: These also receive, amplify and retransmit signal at remote
station. In order to avoid problems due to a small amount of energy reflected by an
inert intermediate object, a useful signal is achieved by using high power output. These
instruments, therefore, use radiation in the form of high energy pulses.
Instruments using visible or near visible wavelengths: These use directly reflected
signal and have the advantage that no complicated and expensive instrument is
required at the remote station. Hence, special reflectors are often used in order to
ensure good return.
Reflectorless EDMI Some EDMI measure distance without using reflecting prism - the
measuring surface itself acts as reflector. In such instruments, the range of
measurements is small (usually 100 to 300 m) depending upon the light conditions
(cloudy days and night darkness provide better measurements).

37. • Filter: The internal beam passes through a variable-density filter and is reduced in
intensity to a level equal to that of the returned external signal which enables a more
accurate measurement.
• Amplifier: These filtered signals are converted to electrical energy while maintaining
the phase-difference. These signal are weak and are amplified by an amplifier.
• Phase discriminator: Phase discrimination is carried out by this component. A phase
meter converts the phase difference into direct current with magnitude proportional
to the differential phase which is subsequently displayed as the distance measured.
• Display unit:The display unit provides results of range measurement on LCD panel.
Fig. Phase difference
measurement principle.

38. The Transmitter uses a GaAs diode that emits amplitude-modulated (AM)
infrared light. A crystal oscillator precisely controls the frequency of modulation.
The modulation process may be thought of as similar to passing light through a
stovepipe in which a damper plate is spinning at a precisely controlled rate or
frequency. When the damper is closed, no light passes. As it begins to open, light
intensity increases to a maximum at a phase angle of 90° with the plate
completely open. Intensity reduces to zero again with the damper closed at a
phase angle of 180°, and so on. This intensity variation or amplitude modulation
is properly represented by sine waves.
A Beam splitter divides the light emitted from the diode into two separate
signals: an external measurement beam and an internal reference beam.
WORKING

39. • By means of a Telescope mounted on the EDM instrument, the external
beam is carefully aimed at a retroreflector that has been centered over the
point at the line’s other end.
• The internal beam passes through a variable-density filter and is reduced in
intensity to a level equal to that of the returned external signal, enabling a
more accurate observation to be made.
• Both internal and external signals go through an interference filter, which
eliminates undesirable energy such as sunlight. The internal and external
beams then pass through components to convert them into electric energy
while preserving the phase shift relationship resulting from their different
travel path lengths. A phase meter converts this phase difference into direct
current having a magnitude proportional to the differential phase. This
current is connected to a null meter that is adjusted to null the current. The
fractional wavelength is measured during the nulling process, converted to
distance, and displayed.

40. Fig. Generalized EDM Process

41. Error Sources in EDMI
Measurement with EDMI has the following error sources which have to be
accounted for while reporting the distance (Kennie and Petrie, 1990):
(i) Instrument operation errors: One has to be careful for precise centering at the
master and slave station pointing/sighting of reflector entry of correct values of
prevailing atmospheric conditions
(ii) Atmospheric errors: Meteorological conditions (temperature, pressure,
humidity, etc.) have to be taken into account to correct for the systematic error
arising due to this. These errors can be removed by applying an appropriate
atmospheric correction model that takes care of different meteorological
parameters from the standard (nominal) one.
(iii) Instrument error: Consists of three components - scale error, zero error and
cyclic error. These are systematic in nature.