Lesson: Radiation,
Intersection and traversing
Methods of Plane table Surveying
1.Radiation method
2. Intersection method
3. Traversing method
1.RADIATION METHOD
The plane table is set up over only one
station from which the whole traverse can be commanded. It is suitable for
survey of small areas.
station from which the whole traverse can be commanded. It is suitable for
survey of small areas.
Procedure:
1) Select a point “O ” so that all points
to be located are visible from it.
to be located are visible from it.
2) Set up the table at “O”, level it, and
do centering.
do centering.
3) SELECT A POINT “O” on the sheet so that
it is exactly over station “O” on
it is exactly over station “O” on
4) Mark the direction of the magnetic meridian
5) Centering the alidade on “O” BISECT the
objects of traverse A, B, C and D.
objects of traverse A, B, C and D.
6) Measure the distances OA, OB, OC and OD
and plotted to convenient scale to locate a, b, c and d respectively
and plotted to convenient scale to locate a, b, c and d respectively
7) Join the points a, b, c and d on the
paper.
paper.
Fig. 8.1 Radiation method
2.INTERSECTION METHOD
In this method the plane table is shifted
to a known distance in a particular direction marked on the ground and the line
of sights are drawn to make intersection of the radial lines already drawn from
the first set up of the instrument.
to a known distance in a particular direction marked on the ground and the line
of sights are drawn to make intersection of the radial lines already drawn from
the first set up of the instrument.
PROCEDURE:
1) Select two points P and Q such that the
points (building corners) to be plotted are visible from their stations.
points (building corners) to be plotted are visible from their stations.
2) Set the table on P and locate on the
sheet.
sheet.
3) Pivot on P bisect Q draw a ray.
4) Measure the distance PQ and locate Q on
the sheet to a convenient scale.
the sheet to a convenient scale.
5) Now PQ is known as the base line.
6) Pivot ‘P’ bisects the inaccessible
objects A and B (building corners) and draw rays.
objects A and B (building corners) and draw rays.
7) Shift the table to ‘A’ such that P is
over Q and do temporary adjustments.
over Q and do temporary adjustments.
8) Place the alidade along QP and the rotate
the table till P is bisected, clamp table.
the table till P is bisected, clamp table.
9) Pivot on Q bisect the objects A and B
and draw rays.
and draw rays.
10) The instruction of rays drawn from P
and Q will give the points A and B.
and Q will give the points A and B.
11) To check the accuracy measured AB and
compare with plotted distance AB.
compare with plotted distance AB.
12) The same procedure is applied for
other features of the campus. each point is bisected from two stations.
other features of the campus. each point is bisected from two stations.
Fig. 7.2 Intersection method
3.TRAVERSE METHOD
We can traverse an area with the plane
table along the boundry to prepare the map or plan of the area.
table along the boundry to prepare the map or plan of the area.
PROCEDURE:
1) Select the traverse stations A,B,C,D,E
etc on the ground.
etc on the ground.
2) Set the table on starting station ‘a’
and perform temporary
and perform temporary
adjustments.
3) Mark the magnetic meridian.
4) Locate A on the sheet as ‘a’.
5) Pivot on ‘a’ bisect the next station B
and draw a ray
and draw a ray
6) Measure the distance AB and locate ‘b’
on the sheet with a suitable scale.
on the sheet with a suitable scale.
7) Shift the table to next station B, set
the table over B, and do temporary adjustments.
the table over B, and do temporary adjustments.
8) Place the alidade along ‘ba’ and bisect
A for doing orientation of plane table.
A for doing orientation of plane table.
9) Pivot on b bisect c draw a ray
10) Measure the distance BC and locate ‘c’
on the sheet with the suitable scale.
on the sheet with the suitable scale.
11) Report the same procedure at every
successive station until the traverse is completed.
successive station until the traverse is completed.
NOTE: By using radiation method,
intersection and traversing methods we can locate the points on the paper,
which were already on the ground. By using algebraic formulae, we can calculate
the area of the given land.
intersection and traversing methods we can locate the points on the paper,
which were already on the ground. By using algebraic formulae, we can calculate
the area of the given land.
FORMULAE:
1) Area of a triangle = ½ * base *height
2) Area of a square = side * side
3) Area of a rectangle = length * breadth
4) Area of a trapezium = ½ * (a + b) * h
A, b are the parallel sides. h is the distance between parallel sides.
Fig 7.3 Traversing method
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