Plane Table Surveying.

1. Plane Table Surveying
Branch : civil Engineering (3rd Sem)

2. Presented by:
Chikhaliya Khushali .P : 151260106007
Jain Mayuri .B : 151260106013
Lashwani Nikita .M : 151260106020
Mankar Nikita .S : 151260106021
Shah Reema .S : 151260106033
Contractor Shila .U : 151260106036

3. Principle:
The principle of Plane Tabling is
parallelism, meaning that the rays drawn
from stations to objects on the paper are
parallel to the lines from the stations to
the objects on the ground.

4. Accessories:
1) The Plane Table
2) The Alidade
3) The Spirit Level
4) The Compass
5) U-fork with Plumb Bob

5. 1) The Plane Table
 The plane table is
a drawing boardof
750mm x 600mm
size made of well-
seasoned wood .
 The bottom surface
consists of a
threaded circular
plate for fixing the
table on the tripod
stand by a wing
nut.

6. 2. The Alidade
 The function of alidade is to sight
objects.
 There are two types of alidade:
1.Plain Alidade
2.Telescopic Alidade

7. 2) The Alidade
 Plain Alidade:
o The plain alidade
consists of a metal or
wooden ruler of length
about 50 cm.
o One of its edges is
bevelled and is known
as the fiducial edge.It
consists of two vanes at
both ends which are
hinged with ruler.
o One is known as object
vane and carries a
horse hair, the other side
is called the sight vane
and has a narrow slit.
 Telescopic Alidade:
o The telescopic alidadde
consists of a telescope
meant for inclined sight
or sighting distant objects
clearly.
o This alidade has no
vanes at the ends, but is
provided with fiducial
edge.

8. 3) The Spirit Level
 The spirit level is
meant for levelling
the plane table.
 The spirit level is a
small metal tube
containing a small
bubble of spirit.
 The bubble is
visible on the top
along a graduated
glass tube.

9. 4) The Compass
• The compass is meant for marking
the north direction on the map.
• There are two types of compass:
1.Trough Compass
2. Circular Box Compass

10. 4) The Compass
 Trough Compass:
o The Trough
Compass is a
rectangular box
made of non-
magnetic metal
containing a
magnetic needle
pivoted at the
centre.
o This compass
consists of a ‘0’
mark at both ends
 Circular Box
Compass
o It carries a pivoted
magnetic needle at
the centre.
o The box is fitted on a
square base plate.
o Sometimes two
bubble tubes are
fixed at right angles
to each other on the
base plate.

11. 5) U-fork with Plumb Bob
 The U-fork is a metal strip bent in the
shape of a ‘U’ having equal arm
lengths.
 The top arm is pointed and the bottom
arm carries a hook for suspending a
plumb bob.

12.  Orientation:
 The method of setting up the plane
table at each of the successive
stations parallel to the position it
occupied at the starting is known as
orientation.
 There are two methods:
1. Orientation by magnetic needle.
2.Orientation by Back sighting.
 Orientation by back sighting is the
most preferred and accurate method.

13. 1.Orientation by Magnetic
Needle
 The north line is marked on the top right
corner of the sheet.
 When the plane table is shifted from
one station to another, the table is
oriented with the help of magnetic
needle.
 The compass is kept along the north
line marked on the earlier station, and
the table is rotated so that the needle is
parallel to the north line.
 Then centering and levelling of the table

14. 2.Orientation by Back sighting
 The table is set up on first station and
next station is bisected with the help of
alidade, and line is drawn with
appropriate scale.
 On moving the table to the next station,
the table is orientated with the help of
alidade.
 The alidade is kept parallel to the
previously drawn line, and the table is
rotated so as the previous station is

15. Methods of Plane Tabelling
 There are four distinct methods of
plane tabelling:
1. Radiation
2. Intersection
3. Traversing
4. Resection

16. 1. Radiation:
 In the radiation method, the direction
of the objects or points to be located
are obtained by drawingradial lines
along fiducial edge of the alidade after
getting the objects or pointsbisected
along the line of sight of the alidade.
 The horizontal distances are then
measured and scaled off on the
corresponding radial lines to mark
their positions on the drawing.

17. 1. Radiation

18. 2. Intersection
 In intersection method, the objects or oints
to be located are obtained at the point of
intersection of radial lines drawn from two
different stations.
 In this method, the plotting of plane table
stations are to be carried out accurately.
Checking is important and thus done by
taking third sight from another station.
 The intersection method is suitable when
distances of objects are large or cannot be
measured properly. Thus, this method is
preferred in small scale survey and for
mountainous region.

19. 2. Intersection

20. 3. Traversing
 This method is used to plot a traverse
in cases stations have not been
previously plotted by some other
methods.
 In this method stations are first
selected. The stations are plotted by
method of radiation by taking back
sight on the preceeding station and a
fore sight to th following station.

21. 3. Traversing

22. 4. Resection
 Resection is the process of
determining the plotted position of the
station occupied by the plane table, by
means of sights taken towards known
points, locations of which have been
plotted.
 There are four methods of resection:
a. By Compass
b. By Back Sighting
c. By two point problem
d. By three point problem

23. 4. Resection

24.  Two Point Problem
 In this problem, two well defined
points whose positions have already
been plotted on the plan are selected.
Then, by perfectly bisecting these
points, a new station is established at
the required position.

25.  Two Point Problem

26.  Three Point Problem
 In this problem, three well defined
points are selected, whose position
have already been plotted on map.
Then, by perfectly bisecting these
three well defined points. A new
station is required in order to solve this
problem. This is directly placed at the
required position. The problem may be
solved by following methods:
 Bessel’s Method
 Mechanical Method

27. Three Point Problem

28. Advantages of Plane
Tabelling
 It is simple and cheaper than the
theodolite sirvey.
 It is most suitable for small scale
maps.
 No great skill is required to produce a
satisfactory map.
 It is useful in magnetic areas where
compass may not be used.
 The mistakes in writing field books are
eliminated.

29. Disadvantages of Plane
Tabelling
 It is not intended for very accurate
work.
 It is not suitable in monsoon.
 It is essentially a tropical instrument.
 Due to heaviness, it it inconvinient to
transport.
 Since there are so many accessories,
there are chances of them being lost.

30. oErrors in Plane Tabelling
 The various sources of errors can be
classified as:
◦ Instrumental errors
◦ Personal Errors
◦ Errors in plotting

31. •Instrumental Errors
1. The surface of the table may not be
perfectly leveled.
2. The fiducial edge of the alidade might
not be straight.
3. The vanes may not be vertical.
4. The horsehairs may be loose or
inclined.
5. The table may be loosely joined on the
tripod.
6. The needle of the magnetic compass
may not be perfectly balanced.

32. • Personal Errors
1. Leveling of the table may not be
perfect.
2. Table may not be centered perfectly.
3. Orientation of the table might not be
perfect.
4. Table might not be perfectly clamped.
5. Objects may not be bisected perfectly.
6. Alidade may not be correctly centered
on the station point.
7. Rays might not be drawn accurately.
8. Alidade may not be centered on the
same side of the paper through out the
work.

33. • Plotting Error
1. A good quality pencil with a very
pointef end may not have been used.
2. An incorrect scale may be used by
mistake.
3. Errors may result from failure to
observe the correct measurement
from the scale.
4. Unnecessary hurry at the time of
plotting may lead to plotting errors.

34. Important Points:
1. Ground shall be marked as A, B,
C..etc. And points on paper shall be
marked as a. b. c.. Etc.
2. The rays from survey stations to the
objects shall be drawn by dashed
lines.
3. The alidade should be properly
pivoted while sighting the objects.
4. The first survey station and the scale
of the map shall be chosen such that
the entire area can be plotted on the

35. Important Points:
5. While establishing magnetic north on
the paper using trough compass,
things causing local attraction shall
be kept away of the table.
6. The plane table should be clamped
after centering and leveling. The
table should rotate at the time of
orientation.