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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.
Dumpy levels/ Automatic
levels
   A dumpy
    level/automatic
    level, is an optical
    levelling instrument
    used in surveying
    to transfer
    measurements or to
    set horizons.
                    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.
Practical Time
                      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.
Practical Time
                  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 axes—
    the 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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posted:12/2/2012
language:English
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