LEVELLING STAFF

Levelling staffs is also required for levelling along with a level. Levelling staff is a rectangular rod with graduations. The staffs are provided having metal shoes at its bottom to resist wear and tear. The foot of the shoe represents zero reading. Levelling staff may be divided into two groups:

(a) Self reading staff  (b) Target staff.

(a) Self reading staff: This staff reading is read by the instrument man through telescope directly. One metre length is divided into 200 subdivisions in a metric system staff, each of uniform thickness of 5 mm. All of the divisions are marked with black in a white background. Decimetres and Metres are written in red colour as shown in figure. The three types of self reading staffs are available:

(a) Solid staff: Solid staff is a single piece of 3 m.

(b) Folding staff: A staff of two pieces each of 2 m which may be folded one over the other. (c) Telescopic staff: With upper one solid and lower two hollow a staff of 3 pieces. The upper part may slide into the central one and the central part may go into the lower part.

Each length by means of brass spring can be pulled up and held in position. The total length can be 4 m or 5 m.

   (a) Self-reading staff                             (b) Telescopic staff                            (c) Target staff

(ii) Target staff: Instrument man finds it hard to read self reading staff If the sighting distance is more. In such type of case a target staff shown in can be used. Target staff is similar to self reading staff, but having a movable target. Target is oval or circular shape, painted white and red in alternate quadrant. At the centre it is fitted with a vernier. Until its centre is in the horizontal line of sight the instrument man directs the person holding target staff to move the target. Then target man reads the target and is recorded.