2. Surveying
Primary divisions of surveying:
1. Plane Surveying
2. Geodetic Surveying
Plane surveying does not take into account the curvature of
the earth’s surface, and the surface of the earth is treated as a
plane surface.
If the area to be surveyed is more than 1000 km2, the angles
measured on the surface of the earth can not be in a plane
surface, but are in a curved surface.
Therefore, Geodetic surveying (which consider curvature of
earth) is used for achieving high precision for large areas.

3. Classification of Surveying
Classification of surveying broadly based on:
1. The function of survey
2. Instruments employed
Classification based on
Classification based on
function of survey:
Instruments Employed:
Land surveying
Chain survey
City surveys
Compass survey
Route surveys
Plane-table survey
Mine surveys
Levelling survey
Geological surveys
Photogrammetric survey
Military surveys etc.
EDM survey

4. Principles of surveying
1. Fixing a point in relation to points
already fixed
3. Working from the whole to the part

5. Definitions of some basic terms
Level surface: is the equipotential surface of the earth’s gravity field.
- A body of still water provides the best example of a level surface.
Horizontal line: A line tangent to a level surface is a horizontal line.
Horizontal plane: is a plane which is tangential to a level surface at a
particular point.
Horizontal angle: An angle measured between two intersecting lines
in a horizontal plane.
Vertical Line: is a line perpendicular to the horizontal plane
Vertical Plane: A plane containing a vertical line
Vertical Angle: Angle between two intersecting lines in a vertical
plane
Elevation: The vertical distance of a point from an assumed datum or
mean sea level.

6. Difference between a PLAN and a MAP
The distinction between plan and map is arbitrary. It is difficult
to say exactly when a plan becomes map.
In general a PLAN is ORTHOGRAPHIC REPRESENTATION of
features on or near earth on a horizontal plane. The earth’s
curvature is not taken into account. Therefore preferable for
smaller areas to avoid distortions due to curvature of the earth.
A MAP is also a graphical representation of features but differs
from a PLAN when the scale is small and is constructed usinga
projection system other than ORTHOGRAPHIC. In general MAPS
will give some additional information such as about the
topography with the help of contours.

7. Land Surveying
Need:-
To secure necessary data of a part of land for the purpose of
demarcating its boundaries, determining its area, preparing its plan
or map, execution of engineering project etc.
Collection of Data:-
Collection of data can be done by any one or combination of surveying
methods.
Ex;- Chain surveying, compass surveying, theodolite surveying,
remote sensing etc.
Factors controlling the type of surveying:-
7. Depending on accuracy required
8. Extent and type of the area to be surveyed
9. Time available for the survey work
10.Economic aspects

8. Execution of surveying
Surveyor has to choose the best approach so
that work can be completed
within given time-frame
and
available funds.

9. Measurement of Horizontal Distances
The commonly used techniques in the basic
engineering are:
Pacing
Measuring Wheel
Taping and/or Chaining
Electronic distance measuring devices
Optical devices

10. Pacing
 A pace is defined as ONE STEP
 A stride is consider TWO steps
 The ability to pace distance is very useful
 A person can determine their pace by counting the number
of paces necessary to walk a distance that has been
previously measured.

11. Measuring Wheels

12. Tape and Chain

13. Electronic Distance Measurement (EDM) Systems
EDMs are very useful in measuring distances that
are difficult to access or long distances

14. Chain Surveying
Chain surveying the simplest method of surveying in which only linear
measurements are made and no angular measurements are taken.
The area to be surveyed is divided into a number of triangles and the sides
of the triangles are directly measured in the field.
Since the triangle is a simple plane geometrical figure, it can be plotted
from the measured length of its sides alone.
In chain surveying, a NETWORK of TRIANGLES is preferred.
Preferably all the sides of a triangle should be nearly equal having each
angle nearly 60o to ensure minimum distortion due to errors in
measurement of sides and plotting.
Generally such an ideal condition is not practical always.
Usually attempt should be made to have WELL CONDITIONED TRIANGLES
in which no angle is smaller than 30 o and no angle is greater than 120o.

15. Chain Surveying
The arrangement of triangles to be adopted in the field depends
on the shape, topography and the natural or artificial
OBSTACLES met with.
Chain surveying is suitable for the following cases:
2. Ground fairly level and open with simple details
3. Large scale plans (1 cm = 10 m)
4. Extent of the area comparatively small
Chain surveying is unsuitable for the following cases:
7. Area crowded with many details
8. Wooded countries
9. Undulating areas
10. Extent of large area

16. Chain Surveying
Definitions:
Main survey stations
-Is a point where TWO SIDES OF A TRIANGLE MEET.
- THESE ARE THE POINTS AT THE BEGINNING AND AT THE END OF
THE CHAIN LINE.
Tie stations (or) subsidiary stations:
-These are the points selected on the main survey lines for running
auxiliary lines.
Main survey lines:
- These are chain lines joining the main survey stations
Tie or subsidiary lines
-The chain lines joining the tie stations or subsidiary stations are
called as tie or subsidiary lines.
-These lines help in locating the interior details which are far away
from the main survey lines.

17. Chain Surveying
Definitions:
Base Line
- the longest of the main survey line
- various survey stations are plotted w.r.t. this line.
Check Lines:
-Those lines which are run to check the accuracy of the field work are called
as check lines or proof lines.
-The length of the check line in the plan must agree with its measured length
in the field.
- each triangle must be provided with a check line.
Offsets:
- Offsets are lateral distances measured from survey lines
-Offsets are taken from survey lines to determine the locations of details.
-Perpendicular offsets are called as simply “OFFSETS”
-Oblique offsets are called as oblique offsets.

18. Chain Surveying
Tape and Chain

19. Chain Surveying
Metric surveying chains:
Length of chain: 20 m or 30 m
Number of links per meter length : 5
Length of each link : 20 cm
Tallies are provided at every 5 m
Small brass rings are provided at every meter except where
tallies are provided.
Metallic tape:
Length of tape: 20 m or 30 m
The linen tape is reinforced with fine brass or copper wires
to prevent stretching or twisting of fibres and is then called
as a metallic tape.

20. Chain Surveying
Arrows:
These are also called as marking or chaining pins
10 arrows are provided along with each chain.
Used to mark end of the chain during the process of
chaining.
Cross Staff: - used to make perpendicular lines

21. Basic Trignometry
C a A2 + B2 = C2
B
b c a+ b+ c = 180o
A
sin b = B / C
cos b = A / C
tan b = B / A