Description

Cross Staff :

It is the simplest instrument for setting out right angles on a survey line. It has a frame containing two pairs of opposite slits mounted on a pole. The pole can be used to fix the instrument on the ground.

Cross Staff has three types

Open cross-staff: Two pairs of vertical slits are present which gives two lines of sight at right angles.
French cross-staff: It has a hollow octagonal box set up on a pole. On each face, vertical slits are cut in the middle for sighting. The lines of sight are at an angle of 45° to one another.
Adjustable cross-staff: It has two cylinders of equal diameter with sighting slits placed on each other. The upper box can be rotated and is provided with a vernier to take measurements. The lower box has graduations of degrees and its subdivision. Any angle can be set out with the help of this instrument.