Theory
In the case of a dumpy level the line of sight its perpendicular to the vertical axis. In the case of tilting level however the line of sight can be tilted slightly without tilting the vertical axis. Thus the line of sight and the vertical axis need not be exactly perpendicular to each other this feature therefore helps in quick leveling. The instrument is leveled roughly by the three foot screws with respect either to the bubble tube or small circular tube. Thus making the vertical axis approximately vertical, while taking the sight to a staff the line of sight is made exactly horizontal by centering the screw which tilts the telescope with respect to the vertical axis. It is however essential that the observer should have the view of the bubble tube while sighting staff.
Instrument required
1. Tilting Level
2. Tripod
Diagram
Construction
The construction of a tilting level is as same as the dumpy level except some component parts. The other component parts of a tilting level are same as the dumpy level. The component part which is differ from dumpy level is
1. The tilting screw : When the sight is taken to a staff the line of sight is made exactly horizontal by bringing the bubble in center, tilting the telescope with respect to the vertical axis by mean of a fine pitched screw which is provided below the telescope called as tilting screw. It is due to the tilting screw that leveling can be done much quicker.
Temporary adjustment
1. Centering : centering set up the level on a firm ground bring the two small cross bubble to the centre of their run by means of foot screw in the usual way. If there is a circular level instead of two cross levels bring it to the centre of its run. The vertical axis is thus brought approximately vertical.
