There are two types of operations involved in centring of plane table.

• the centring with reference to already plotted position of the station. In this case, the pointed end of the upper arm of a U-fork is held at the plotted position of the station and the table is shifted and adjusted in such a way that the tip of the plumb bob points exactly over the ground station.
• the centring with reference to ground location of the station. In this case, the tip of the plumb bob attached to a U-frame is placed exactly over the ground point which is required to be transferred. The point corresponding to the tip of the pointed arm of the U-frame provides the transferred position on the table.

However, the accuracy with which centring is being carried out depends upon the scale of plotting.

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