Leveling Instruments used in Surveying.

Leveling Instruments used in Surveying.

• Leveling Instruments used in Surveying.
• Types of Leveling Instruments
• 1.Dumpy level.
• 2. Wye or Y level.
• 3. Cooke’s reversible level.
• 4. Cushing’s level.
• 5. Tilting Level.
• 
  
• Levelling instruments are employed for determining the relative heights of different points on the earth’s surface.
  A level essentially consists of a telescope to which a bubble tube is attached such that the axis of the bubble tube and the line of collimation of the telescope are parallel to each other.
  The instrument is provided with leveling screws by which the bubble tube is centered, and the line of collimation is brought into a horizontal plane.
• The levelling instrument irrespective of its type essentially consists of:
  1. Leveling head with foot screws
  2. Telescope and
  3.  level or bubble tube;
  The Leveling head usually consists of two parallel plates the upper plate is supported over the lower plate by three or four-foot screws or leveling screws by which the instrument may be leveled.
  Most of the modern Levelling instruments are designed to have three-foot screws because they are easily leveled.
  The telescopes used in surveying instruments consists of metal tubes, one moving axially within the other.
  There are mainly two types of telescope, (1) the external focusing telescope, and (2) the internal focusing telescope.