MODULE CONSIST OF ALL THE RELEVANT CONTENTS REGARDING THE TACHEOMETRY AS PER THE SYLLABI OF DBATU, LONERE FOR SYBTECH CIVIL ENGINEERING

1. Tachometric surveying
Prepared By-
Prof. Basweshwar S. J.

2. Prepared By-
Prof. Basweshwar S. J.

3. Advantages of Tacheometric surveying
It eliminates use of chain and tape. .
We can do survey in area like Hill and mountain where it is very
difficult to do survey by other methods.
If we not need very high standards and accuracy then this is right
method.
It require low amount of time compare to other ways of
surveying.
Because Tacheometry is indirect method that we do not require
some instrument that is necessary in plan table surveying or in
theodolite surveying.
Prepared By-
Prof. Basweshwar S. J.

4. Disadvantages of Tacheometric
surveying
Major disadvantage of tacheometric surveying is
that, it is not used where higher accuracy is
required.
Prepared By-
Prof. Basweshwar S. J.

5. Applications
In rough country, both horizontal and vertical
measurements are tedious and chaining is in accurate,
slow and difficult.
when obstacles such as steep and broken ground,
stretches of water.
In locating contours and filling in detail in a topographic
survey, this method is usually the quickest & best.
When area to be surveyed is very large and accuracy
required is less.
Prepared By-
Prof. Basweshwar S. J.

6. Applications
Preparation of topographic maps which require both
horizontal distances and elevations.
Survey work in difficult terrain where direct methods
are inconvenient.
Filling details in a traverse.
location surveys for highways, railways, canals, etc.
hydrographic surveys.
Prepared By-
Prof. Basweshwar S. J.

7. Prepared By-
Prof. Basweshwar S. J.

8. Prepared By-
Prof. Basweshwar S. J.

9. Stadia method
• It is the most prevalent method for
tacheometric surveying.
• In this method, the telescope of the
theodolite is equipped with two
additional cross hairs, one above
and the other below the main
horizontal hair at equal distance.
• These additional cross hairs are
known as stadia hairs.
Tangential Method
• The tangential method of tacheometry is being
used when stadia hairs are not present in the
diaphragm of the instrument.
• In this method, the staff sighted is fitted with
two big targets (or vanes) spaced at a fixed
vertical distances.
• Vertical angles corresponding to the vanes,
say q1 and q2 are measured.
• The horizontal distance, say D and vertical
intercept, say V are computed from the values
s (pre-defined / known) q1 and q2 .
• This method is less accurate than the stadia
method.Prepared By-
Prof. Basweshwar S. J.

10. Fixed Hair Method: In the fixed hair
method the cross hairs of the diaphragm
are kept at a constant distance apart and
the staff intercept varies with the
horizontal and vertical position of the
staff with respect to the Theodolite.
Movable Hair Method: In this method
the staff intercept between the lower hair
and the upper hair is kept constant by
moving the horizontal cross hairs in the
vertical plane.
Prepared By-
Prof. Basweshwar S. J.

11. 2. Additive constant
B=(f+d) where,
f=focal length of the lens
d= horizontal distance
between instrument axis to
optical centre of a lens The
value of additive constant.
varies from 0.15 m to 0.60
m.
Prepared By-
Prof. Basweshwar S. J.

12. In tachometric surveying, instrument used is known as a tachometer.
With the help of a tachometer observations (stadia readings and vertical
angles) are taken and horizontal and vertical distances are determined by
using formulae.
Before doing calculations we should known the values of two constants for
a tachometer to be used for survey work.
Generally their values are mentioned in the catalogue supplied by
the manufacturer.
Also the constants may be determined by:
1.Laboratory measurement
2. Field measurementPrepared By-
Prof. Basweshwar S. J.

13. Anallatic lens
It is an additional lens generally provided in the external focusing
tachometer between object glass & eyepiece
Advantages of anallatic lens:
1) For calculation of horizontal & vertical distances constant (f+c)=0,
if tacheometer is provided with anallatic lens.
2) Calculation becomes simple.
Disadvantages of anallatic lens:
1. The anallatic lens absorbs some of the incident light which
consequently results in reduction of the brightness of the image.
2. It also adds to the initial cost of the instrument because of one extra
lens.
Prepared By-
Prof. Basweshwar S. J.

14. Auto reduction Tachometer
Prepared By-
Prof. Basweshwar S. J.

15. FIELD WORK
• Set up the instrument.
• Set the vernier of the vertical circle to zero.
• With the altitude level at the center of its run, measure the height of the instrument with a measuring
tape accurately.
• Orient the instrument.
• Hold the staff on the benchmark and take the bearing, read the vertical angle and the top, bottom, and axial hair
readings.
• If any benchmark is not nearby the area of traversing, Fly level may be carried out.
• After all the representative points are located from the first station, take a foresight at the second station and
note down the bearings.
• Vertical angle and the staff readings corresponding to the top, bottom and the axial hairs.
• As each station is sighted twice two Values for the distances and elevations of the stations are obtained which
should be within the permissible limits; otherwise, the work should be repeated.
Prepared By-
Prof. Basweshwar S. J.

16. ELECTRONIC DISTANCE MEASURMENTS [EDM]
• Electronic distance measuring instrument is a surveying instrument for measuring
distance electronically between two points through electromagnetic waves.
• The method of direct distance measurement cannot be implemented in difficult
terrains.
• When large amount of variation in the terrain or large obstructions exist, this
method is avoided.
• As an alternative to this optical distance measurement method was developed.
Still it gained a disadvantage of limited range of measurement.
• It is limited to 15 to 150m with an accuracy of 1 in 1000 to 1 in 10000. Above all
we have EDM with an accuracy of 1 in 105, having a distance range of 100km.
Prepared By-
Prof. Basweshwar S. J.

17. Sun light or artificially generated electromagnetic wave consists of waves
of different lengths. The spectrum of an electromagnetic wave is as
shown below:
Prepared By-
Prof. Basweshwar S. J.

18. Types of Electronic Distance Measurement Instrument
Microwave instruments Infrared wave instruments Light wave instruments.
These instruments make use
of microwaves.
In this instrument amplitude
modulated infrared waves
are used.
These instruments rely on
propagation of modulated
light waves.
The instrument needs only
12 to 24 V batteries.
Prism reflectors are used at
the end of line to be
measured.
Light waves are most suited
way in this instrument.
They are light and highly
portable. Tellurometers can
be used in day as well as in
night.
These instruments are light
and economical and can be
mounted on theodolite.
These instruments are also
very useful for civil
engineering projects.
The range of these
instruments is up to 100 km.
With these instruments
accuracy achieved is ± 10
mm. The range of these
instruments is up to 3 km.
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.
Prepared By-
Prof. Basweshwar S. J.

19. From the transit time and known velocity, the distance can be easily
measured. Now to solve the problem arise due to difficulty in starting the
timer at B, a reflector can be placed as shown below instead of a receiver at
B.
Fig. Transit measurement arrangement with the help of a EDM and a reflector
Prepared By-
Prof. Basweshwar S. J.

20. ERRORS in Electronic Distance Measurement
Personal Errors Instrumental Errors Natural Errors
Inaccuracy in initial setups of EDMs
and the reflectors over the preferred
stations
Calibration errors Atmospheric variations in
temperature, pressure as well
as humidity.
Instrument and reflector
measurements going wrong
Chances of getting
maladjusted time to time
generating frequent errors.
Micro wave EDM
instruments are more
susceptible to these.
Atmospheric pressures and
temperature determination errors
Errors shown by the
reflectors.
Multiple refraction of the
signals.
• The advantage of using EDM instruments is the speed and accuracy in measurement.
• Several obstacles to chaining are automatically overcome when these instruments are
used.Prepared By-
Prof. Basweshwar S. J.

21. STUDY AND USE OF TOTAL STATION
• Total station is a surveying equipment combination of Electromagnetic Distance
Measuring Instrument and electronic theodolite.
• It is also integrated with microprocessor, electronic data collector and storage system.
• The instrument can be used to measure horizontal and vertical angles as well as
sloping distance of object to the instrument.
Capability of a Total Station
Microprocessor unit in total station processes the data collected to compute:
• Average of multiple angles measured.
• Average of multiple distance measured.
• Horizontal distance.
• Distance between any two points.
• Elevation of objects and
• All the three coordinates of the observed points.
Prepared By-
Prof. Basweshwar S. J.

22. Prepared By-
Prof. Basweshwar S. J.

23. Important Operations of Total Station
Distance Measurement- range varies from 2.8 km to 4.2
km.
Angle Measurements- angle measurement varies from 2 to
6 seconds.
Data Processing- computes the horizontal distance and X,
Y, Z coordinates.
Display- capable of displaying horizontal distance, vertical
distance, horizontal and vertical angles, difference in
elevations of two observed points
Electronic Book- capacity of electronic note book varies
from 2000 points to 4000 points data.Prepared By-
Prof. Basweshwar S. J.

24. Prepared By-
Prof. Basweshwar S. J.

25. Advantages of Using Total Stations
The following are some of the major advantages of using total station over the
conventional surveying instruments:
1.Field work is carried out very fast.
2.Accuracy of measurement is high.
3.Manual errors involved in reading and recording are eliminated.
4.Calculation of coordinates is very fast and accurate.
5.Corrections for temperature and pressure are automatically made.
6.Computers can be employed for map making and plotting contour and cross-
sections.
7.Contour intervals and scales can be changed in no time.Prepared By-
Prof. Basweshwar S. J.

26. SUBTENSE BAR
Prepared By-
Prof. Basweshwar S. J.

27.  The subtense bar is an instrument used for measuring the
horizontal distance between the instrument station and a station
where the subtense bar is to be set up.
 Substense method is an indirect method of distance determination.
 This method essentially consists of measuring the angle subtended by
two ends of a horizontal rod of fixed length, called a subtense bar.
 In this method a staff or target rod is not necessary, and the theodolite
required is also of the ordinary transit type.
Prepared By-
Prof. Basweshwar S. J.