Plane Table Survey
PLANE TABLE SURVEY (Traverse)
OBJECTIVE
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2.
3.
4.
Orientation of plane table instruments and accessories.
Overall sketch of the field in close traverse with five peg stations.
Two way taping in precision 1:10000.
Adjustment of closing error by graphical method.
INSTRUMENTS REQUIRED
1. Plane table
2. Tape
3. Ranging Rods
4. Plum Bob
5. Tripod Stand
6. Alidade
7. Through Compass
8. U frame or Plumbing Fork
9. Spirit Level or Level Tube
10. Drawing Sheet
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THEORY
INTRODUCTION TO PLANE TABLE SURVEY:
Plane table surveying is a graphical method of surveying in which field work and plotting are
done simultaneously in the field.
The plane table consists of the following:
1. Drawing board mounted on a tripod.
2. Straight edge called an alidade.
THE DRAWING BOARD:
The drawing board is made of well-seasoned wood and varies in size from 40cm x 30cm to 75cm
x 60cm or 50-60 sq. cm.
THE ALIDADE:
Plane Table Survey
The alidade consists of metal or wood straight edge or ruler about 50cm long. The well edge of
the alidade is called fiducially edge.
Types of alidade:
1. Plain alidade
2. Telescopic alidade
THROUGH COMPASS:
This compass is used to mark the direction of the meridian on the paper.
U-FRAME OR PLUMBING FORK:
U-frame with a plumb bob is used for centering the table.
SPIRIT LEVEL OR LEVEL TUBE:
A level tube is used to level the plane table.
SETTING UP THE PLANE TABLE:
The setting up the plane table includes the following three operations.
1. Centering the plane table
2. Levelling the plane table
3. Orientation of plane table
CENTERING THE PLANE TABLE:
The table should be set up at a convinient height for working ,say about 1m. The legs of tripod
should be spread well apart and firmly fixed into 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.
LEVELLING THE PLANE 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.
ORIENTATING THE TABLE:
Plane Table Survey
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 is oriented, the lines on the boards are
parallel to yhe lines on the ground.
There are two main methods of orienting the plane table:
1. Orientation by means of trough compass.
2. Orientation by means of backsighting.
PROCEDURE
1) Select the traverse stations A,B,C,D,E etc on the ground.
2) Set the table on starting station a 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
6) Measure the distance AB and locate b on the sheet with a suitable scale.
7) Shift the table to next station B, set the table over B, and do temporary
adjustments.
8) Place the alidade along ba and bisect 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.
11) Report the same procedure at every successive station until the
traverse is completed.
OBSERVATIONS TABLE
SN
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FORWARD DISTANCE (m)
BACKWARD DISTANCE (m)
AB=28.550
BC=27.700
CD=16.120
DE=14.200
EA=22.720
BA=28.550
CB=27.700
DC=16.120
ED=14.200
AE=22.722
REFERENCE SKETCH OF THE FIELD:
Plane Table Survey
Fig : close traverse of field in plane table survey
RESULT
Hence plane table survey is applied successfully in the field and the sketch of the given field was
plotted correctly calculating the closing error.
DISCUSSION AND CONCLUSION
Hence by using plane table survey overall sketch of the field is plotted correctly. For this a close
traverse is taken around the boundary of the field and then all the features around the field are
plotted by using trough compass and tape.
PRECAUTIONS
1. The position of plane table should be maintained correctly by centering, levelling and by
orientation.
2. All measurements should be taken correctly and carefully.
