basic surveying

1. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
Basic Surveying
Presented By
Er. Ashish B.Jadhav
CO:-Use levelling instruments to determine reduced level of ground
point.

2. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Levelling:
• The art of determining the relative heights of
points on the surface of the earth is termed as
“levelling.”
 Level Surface:
• Level surface is the continuous surface parallel
to the mean spheroid of the earth. The line
representing the level surface is termed as
level line.
• The level line makes right angles to the
vertical line or plumb line at any point.
• It means the any point on level line is
equidistance from the center of earth.
• Even though it is a curved surface, it is
considered as plane surface for smaller area
works

3. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Level Line:
• A line lying throughout on a level surface is a level line. This is
normal to the plumb line at all points.
 Horizontal Plane.
• A horizontal plane through a point is a plane tangential to the
level surface at the point. This is normal to the direction of
gravity at that point.

4. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Horizontal Line:
• Any line lying throughout in a horizontal plane is termed as
“horizontal line.”
 Vertical Plane:
• A vertical plane is any plane containing a vertical line. A
vertical line at any point is a line normal to the level surface at
that point.

5. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Vertical Line:
• A plumb line is an example of a vertical line.
 Datum Line:
• Datum line is the reference line with respect to which the levels
of other station points are fixed.

6. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Mean Sea Level:
• Mean sea level is established by taking the average height of
tides in the sea over a very long period (generally 19years).
• Mean sea level or MSL is used as datum level for all important
surveys of that zone.
• For India mean sea level is at Karachi

7. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Reduced Level:
• Reduced level is the vertical
difference between the level point
and datum line or the mean sea
level.
 Benchmark:
• Benchmark is the point laid above
or below the datum line with a
known elevation.
• Bench mark is considered as
check for the other level points.

8. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Benchmark:
• There are different types of bench
marks are available in the
surveying as follows:
• Great Trigonometrical Survey
benchmarks
• Permanent benchmarks
• Temporary benchmarks
• Arbitrary benchmarks

9. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Great Trigonometrical Survey
Benchmarks:
• Great trigonometrical bench mark
or shortly GTS benchmarks are
very accurate, and they are
established by conducting high
precise surveys.
• GTS benchmarks are decided by
taking mean sea level as datum.
• These are generally established
by higher survey authorities of
particular country in all points of
the country.

10. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Permanent Benchmarks:
• Permanent benchmarks are
established with reference to GTS
benchmarks.
• They are established by local state
government agencies or railways
at railway stations, public
buildings, at bridges etc.
• Permanent benchmarks are useful
for future references also.

11. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Temporary Benchmarks:
• Temporary benchmarks are
created by the surveyors in the
field to mark the point in the field
up to which the survey is
completed.
• Then, it is easier to continue the
survey from that point after large
gap or on the next day of work.
• The temporary bench mark point
should be decided in a way that
the object or point should be
permanently fixed in that position.

12. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Arbitrary Benchmarks:
• In Small survey works or engineering projects it is
important to know the difference in elevation of two
points.
• When this happens, we cannot predict the exact reduced
level of that area with respect to mean sea level.
• So, some fixed points in that area are arbitrarily taken as
bench marks and values are assumed.
• The assumed arbitrary bench mark values may be 50.000
m, 100.000 m, 200.000 m etc.

13. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Line of Collimation:
• The line of collimation or the line of sight is the line joining
the intersection of cross-hairs to the optical center of the
object glass and its continuation.
 Axis of Telescope.
• The axis of a telescope is the line joining the optical center
of the object glass to the center of the eye piece.

14. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Axis of Bubble Tube:
• The axis of bubble tube or level tube is the line tangential to
the longitudinal curve of bubble tube at its middle point.
 Vertical Axis.
• The vertical axis is the line about which the telescope can be
rotated in a horizontal plane.

15. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Back Sight:
• A back sight (B.S) is the first staff reading taken after setting up
the instrument in any position. This will always be a reading on
the point of known elevation.

16. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Fore Sight:
• A fore sight (F.S) is the last staff reading taken before moving the
instrument. This will always be reading on a point whose
elevation is to be determined.
• This reading indicates the shifting of the instrument.

17. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Intermediate Sight:
• An intermediate sight (I.S) is any staff reading taken on the point
of unknown elevation after the back sight and before the fore
sight.
• This is necessary when more than two staff readings are taken
from the same position of the instrument.

18. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Change Point:
• A change point (C.P) indicates the shifting of the instrument.
Both back sight and fore sight are taken on a change point.
 Height of the Instrument:
• The height of instrument (H.I) is the elevation of the plane of
collimation when the instrument is leveled (and not the height of
the center of the telescope above the ground level).

19. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.1 Terminologies in Levelling
 Station Point:
• A station point is a point whose elevation is to be determined or a
point which is to be established at a known elevation.
• Therefore, this is the point on which the staff is held and not the
point on which the instrument is set up.

20. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Levels:
• Levels are the different instruments used for leveling in
surveying.
• There are various types of levels such as dumpy level, Y level,
tilting level, Cooke’s reversible level and automatic level
instruments for leveling in surveying.

21. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Dumpy Level:
• Dumpy level is the most commonly used instrument in leveling.
• In this level the telescope is restricted against movement in its
horizontal plane and telescope is fixed to its support.
• A bubble tube is provided on the top of the telescope.

22. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Y Level:
• Y level or Wye-level consists y-shaped frames which supports the
telescope. Telescope cane be removed from the y-shaped supports
by releasing clamp screws provided.
• These y-shaped frames are arranged to vertical spindle which
helps to cause the rotation of telescope.
• Compared to dumpy level, adjustments can be rapidly tested in y-
level.
• But, there may be a chance of frictional wear of open parts of
level.

23. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Tilting Level:
• In this, telescope can be tilted
through about four degrees with the
help of a tilting screw.
• Hence bubble can be easily
centered. But it needs centering of
the bubble before taking every
reading.
• Hence it is useful, if at every setting
of the instrument number of
readings to be taken are few.

24. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Cooke’s Reversible Level:
• Cooke’s reversible level is the
combination of dumpy level and y-
level.
• In this instrument, the telescope can
be reversed without rotation the
instrument.
• Collimation error can be eliminated
in this case because of bubble left
and bubble right reading of
telescope.

25. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Automatic Level:
• Automatic level is like the dumpy
level.
• In this case the telescope is fixed to
its supports.
• Circular spirit can be attached to the
side of the telescope for
approximate leveling.
• For more accurate leveling,
compensator is attached inside the
telescope.

26. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Types of Levels
 Digital Level:
• Digital leveling systems for
surveying rely on an electronic laser
to scan a level staff with bar code
markings.
• This type of level reduces the
chance of human error when
interpreting graduation marks, and a
digital display ensures accurate
readings.
• When job sites need fast and
accurate height determinations,
precision digital leveling equipment
serves as valuable time-saving
technology.

27. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Telescope
• Telescope is used to observe the
distant object through line of
sight provided by its
arrangement.
• In general, the telescope is fixed
to the vertical spindle of dumpy
level so that it can be rotated
along with vertical spindle.
• Parts of Telescope in Dumpy
Level
• Eye piece:- Eye piece is used by
the observer’s eye to view the
distant object.

28. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Objective lens :-
• Objective lens are provided at
the other end of the telescope.
• The objective lens consists of
two parts, the front part consists
convex type lens and the back
part consists concave lens.
• So, the image obtained from the
objective lens is always inverted.

29. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Diaphragm :-
• Diaphragm is provided in front
of the eye piece. It contains
cross hairs made of dark metal
which are arranged in perfect
perpendicular positions. These
cross hairs are used by the eye
piece to bisect the objective
through objective lens.

30. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Focusing screw :-
• Focusing screw is used to adjust
the focus if cross hairs and the
image clarity. The magnification
of eye piece is managed by this
focusing screw.
• Bubble tubes:
• Bubble tubes are provided to
check the level of the
instrument.

31. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Bubble tubes:
• Two bubble tubes are provided
in a dumpy level which are
arranged perpendicular to each
other on the top of the telescope.
• One tube is called as
longitudinal bubble tube and
another is called as cross bubble
tube.
• The instrument is said to be in
perfect position when both the
bubbles of the tubes are at center
or middle of the tube.

32. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Vertical spindle:
• Vertical spindle is located at the
center of the whole instrument.
• The telescope can be rotated in
horizontal direction with respect
to vertical spindle.
• The instrument is connected to
the tripod stand using vertical
spindle.

33. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Tribrach:
• Tribrach plate is parallel to the
leveling head or trivet.
• It is connected to trivet by
leveling screws or foot screws
which can adjust the tribrach
plate.
• The horizontal level of the
instrument can be achieved by
adjusting this tribrach plate.

34. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Foot screws:
• Foot screws are provided to
regulate the tribrach position and
hence the instrument can be
leveled which is known by observing
the bubble tube.
• The tribrach plates can be lowered
or raised using foot screws.
• The position of tribrach is said to be
correct when the bubble in bubble
tube is at center.

35. Department of Civil Engineering Created By Er.A.B. Jadhav Mob.No 9075009500
4.2 Components of Dumpy level
 Dumpy level:
• Levelling head:
• Leveling head is also called as
trivet.
• It contains two triangular shaped
plates which are arranged
parallel to each other.
• Three groves are provided at the
three corners of the plates in
which foot screws are supported.