Plane table surveying
The
method of Surveying in which the field work and plotting are done
simultaneously that is called plane table surveying. It is mainly used for
small and medium scale mapping of comparatively larger areas where great
accuracy is not the main consideration charges for topographical surveys. It is
less costly than a theodolite survey. It is not suitable to work in a wet
climate the equipment essentially consist of a drawing board mounted on tripod
and a state is called an alidade. The alidade is Mainly available in two forms
one is planar alidade and another is telescopic alidade.
Set up for plane table surveying-
To
setup for a plane table surveying,the following three operation are performed-
1.
Levelling- it is the operation of setting up the plane table over a station
point and happy Convent height. The levelling is done by means of levelling
screws or by simply adjust the legs.
2.
Centering- it is the operation in which the plane table is so placed over a
station on the ground that the point on the paper corresponding to the station
occupied is exactly over the station on the ground.
3.
Orientation- it is the operation in which the plane table is turned so that all
lines on the paper are parallel to the corresponding ground.
Methods of plane table surveying-
1.
Radiation- the point is seated on a plane by drawing a Ray from the plane table
station to the point and plotting to scale along the ray the distance measured
from the station to the point. This method is mainly used in small areas which
can be commanded from a single station.
2.
Intersection- the point is on plane by intersection of the wrist drop from two
instrument station for this method. This method is commonly for locating the
distant and inaccessible point, locating the broken boundaries.
3.
Traversing- this method is similar to that of compass traversing. It is mainly
used for running survey lines between stations which have been previously fixed
by other method of serving to locate topographical details. It is also suitable
for the survey of roads, rivers etc.
4.
Resection- this method is used for establishing the instrument station only.
After mixing the stations the detail are located either by radiation or
intersection.
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