Lesson Plane table surveying
Plane Table
Surveying
Surveying
·
Plane table surveying is
a graphical method of surveying in which the field works and the plotting is
done simultaneously. It is particularly adopting in small areas mapping. Plane
table surveying is used for locating the field computation of area of field.
Plane table surveying is
a graphical method of surveying in which the field works and the plotting is
done simultaneously. It is particularly adopting in small areas mapping. Plane
table surveying is used for locating the field computation of area of field.
Merits
·
It is most suitable for
preparing small scale map or surveying small area.
It is most suitable for
preparing small scale map or surveying small area.
·
It is most rapid method.
It is most rapid method.
·
Field book is not
necessary.
Field book is not
necessary.
·
No great skill is
required for satisfactory map.
No great skill is
required for satisfactory map.
·
It is particularly
suitable for magnetic area where prismatic compass is not reliable.
It is particularly
suitable for magnetic area where prismatic compass is not reliable.
·
Contour and irregular
object may be represented accurately.
Contour and irregular
object may be represented accurately.
·
It is less costly.
It is less costly.
Demerits
·
Plane Table Essentially
a tropical instruments.
Plane Table Essentially
a tropical instruments.
·
It is not suitable to
work in wet climate.
It is not suitable to
work in wet climate.
·
There are several
accessories to be carried out and therefore they are likely to be lost.
There are several
accessories to be carried out and therefore they are likely to be lost.
·
It is not suitable for
accurate work.
It is not suitable for
accurate work.
Plane Table essentially
consists of a Drawing board mounted on tripod stand and Alidade.
consists of a Drawing board mounted on tripod stand and Alidade.
1. Drawing board mounted
on tripod
on tripod
A sheet of drawing
paper, called plane table sheet is fastened to the board. Board is made
up of well seasoned wood such as teak of size 40×30 to 75x60cm. it had plane
and smooth top. It is mounted on a tripod in manner that it can be leveled.
Leveling up of the table is done by shifting the legs of tripod. Some tripod
provided with leveling screw or by ball and socket head for accurate leveling.
paper, called plane table sheet is fastened to the board. Board is made
up of well seasoned wood such as teak of size 40×30 to 75x60cm. it had plane
and smooth top. It is mounted on a tripod in manner that it can be leveled.
Leveling up of the table is done by shifting the legs of tripod. Some tripod
provided with leveling screw or by ball and socket head for accurate leveling.
2. Alidade:
Alidade consists of two
vertical sight vane fitted at end the end of straightedge. The straight edge
ruler usually made of brass or teak wood graduated beloved edge. One of the
sight veins is provided with narrow slit and the other with a central vertical
wire or hair. Beveled working edge alidade is called fiducial edge.
vertical sight vane fitted at end the end of straightedge. The straight edge
ruler usually made of brass or teak wood graduated beloved edge. One of the
sight veins is provided with narrow slit and the other with a central vertical
wire or hair. Beveled working edge alidade is called fiducial edge.
Fig. 6.1 Plane table
with Alidade
with Alidade
Accessories used in
Plane Table surveying are
Plane Table surveying are
1. Trough compass
2. U – frame or plumbing
fork
fork
3. Water proof cover.
4. Spirit level or level
tube
tube
5. Drawing sheet
6. Pencil or eraser
Fig. 6.2 Accessories in
Plane Table surveying
Plane Table surveying
Trough compass: The
compass is used to mark the direction of the meridian on the paper.
compass is used to mark the direction of the meridian on the paper.
U- frame or Plumbing
fork: U frame with a plumb bob used for centering the table.
fork: U frame with a plumb bob used for centering the table.
Water Proof Cover: Water
Proof cover protects the sheet from rain.
Proof cover protects the sheet from rain.
Spirit level or level
tube: A level tube is used to level the plane table.
tube: A level tube is used to level the plane table.
Drawing sheet: The
drawing sheet is fixed on the top of the drawing board.
drawing sheet is fixed on the top of the drawing board.
Pencil and eraser: A
pencil is used for constructing lines and eraser is used for erasing lines
after completion of the plan.
pencil is used for constructing lines and eraser is used for erasing lines
after completion of the plan.
Operations involved in
Plane Table Surveying
Plane Table Surveying
SETTING UP THE PLANE
TABLE
TABLE
The setting up the plane
table includes the following three operations.
table includes the following three operations.
1. Centering the plane
table
table
2. Leveling the plane
table
table
3. Orientation of plane
table
table
CENTERING THE PLANE
TABLE:
TABLE:
The table should be set
up at a convenient height for working say about 1m. The legs of tripod should
be spread well apart and firmly fixed in to the ground. The table should be
approximately leveled by tripod legs and judging by the eye. Then the operation
of centering is carried out by means of U-frame and plumb bob. The plane table
is exactly placed over the ground station by U-frame and plumb bob.
up at a convenient height for working say about 1m. The legs of tripod should
be spread well apart and firmly fixed in to the ground. The table should be
approximately leveled by tripod legs and judging by the eye. Then the operation
of centering is carried out by means of U-frame and plumb bob. The plane table
is exactly placed over the ground station by U-frame and plumb bob.
LEVELING THE PLANE
TABLE:
TABLE:
The process of leveling
is carried out with the help of level tube. The bubble of level tube is brought
to center in two directions, which are right angles to each other. This is
achieved by moving legs.
is carried out with the help of level tube. The bubble of level tube is brought
to center in two directions, which are right angles to each other. This is
achieved by moving legs.
ORIENTING THE TABLE:
The process of keeping
the plane table always parallel to the position, which is occupied at the first
station, is known as orientation. When the plane table is oriented, the lines
on the board are parallel to the lines on the ground.
the plane table always parallel to the position, which is occupied at the first
station, is known as orientation. When the plane table is oriented, the lines
on the board are parallel to the lines on the ground.
google-site-verification=2j8Us0psP3GGjD12h0fH6_Z08_sRyWQjNbWcaMV4E9A
