Dumpy levels, Theodolite, and Laser levels.

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Dumpy levels, Theodolite, and Laser levels.

• Aims and objectives
• To identify the differences between the above
  items
• To successfully measure point in a classroom
  using a dumpy level and laser level.
• To identify the markings on the graduation staff
  and how it is read.

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Dumpy levels/ Automatic levels

• A dumpy level/automatic level, is an optical
  levelling instrument used in surveying to
  transfer measurements or to set horizons.

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Line of sight

• The level instrument is set up on a tripod and,
  depending on the type, either roughly or
  accurately set to a levelled condition using foot
  screws (levelling screws). The operator looks
  through the eyepiece of the telescope while an
  assistant holds a tape measure or graduated staff
  vertical at the point under measurement. The
  instrument and staff are used to gather and/or
  transfer elevations (levels). Measurement
  generally starts from a benchmark with known
  height determined by a previous survey, or an
  arbitrary point with an assumed height.

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Practical Time
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Laser Levels

• This rotating laser beam takes the place of a
  construction worker having to sight through the
  telescope of an optical level in order to record
  a level along the collimation axis.
• The laser beam representing the collimation
  axis is received by a sensor that can be attached
  to the levelling staff.
• This sensor is able to slide up and down
  the levelling staff and an audible tone is heard
  to indicate how close to the collimation axis the
  sensor is. When the sensor is moved toward
  the collimation axis the intermittent tone will
  increase in frequency, until a constant tone is
  heard when the sensor and axis are at the same
  height. Many instruments will provide a different
  sounding tone, to indicate the direction of
  travel required.

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Practical Time
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Theodolites

• A Theodolite is an instrument used for measuring
  in both the horizontal and vertical angles.
• A modern Theodolite consists of a movable
  telescope mounted within two perpendicular
  axesthe horizontal or trunnion axis, and the
  vertical axis
• When the telescope is pointed at a desired
  object, the angle of each of these axes can be
  measured with great precision

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