Levelling Staff

It is a device to measure the distance by which the staff station is above or below the line of sight. That could be made of well seasoned timber or aluminum, generally having size of 75 mm × 25 mm, with graduations marked, starting from foot of staff as zero and increasing upwards. The generally used staff (Telescopic staff) is usually 4 meters long with specifications as laid in IS : 1779-1961. It has three telescopic lengths. The top solid piece is about 1.2 meter long slides into the central box of about 1.3 m length. Here the lower base is of 1.5 m length as display in Figure 4. The inner pieces could be pulled out and latched by metal spring clamps to remain stable. The graduation

                                             Figure : Telescopic Levelling Staff

Markings are painted black against the white background. The 4 m long folding staffs usually of aluminum is also available consisting of two 2 m long pieces with hinged joint at middle, along with the locking device. Each meter is divided within 200 divisions along with every graduation 5 mm thick as shown. Invar precision levelling staff might be used when high precision measurements are needed. Invar graduated band is detachable and is fitted strongly on the wooden staff at lower end and held in position at upper end through a spring. The staff is set on an iron base plate and kept vertical through detachable stays. The reading is acquired with the help of a parallel plate micrometer of the telescope.