THEODOLITE LESSON 6
VERTICAL ANGLE
•
When two lines are meeting in a vertical plane, the
angle between them is called “vertical angle”
•
These angles are measured with the help of vertical
(plate) circle and corresponding
verniers “C” and “D”
VERTICAL ANGLES
•
Angle of elevation( Figure-1 )
•
Angle of depression ( Figure- 2 )
MEASUREMENT
OF VERTICAL ANGLES
Let
•
“O” is instrument station
•
“PQ” is the object, say a ranging rod ( Figure-3)
•
Set up theodolite over station “O” and complete the
temporary adjustments accurately with the help of altitude bubble tube
•
Bring index of verniers “C” and “D” to zero degrees
•
Release upper plate (vertical plate) clamp screw and
sight to object “Q” and clamp it firmly.
•
Bisect the object “Q” accurately with help of corresponding slow motion screw
•
Read main scales and corresponding vernier scales “C” and “D”. This angle is called angle of
elevation
•
Release the upper plate (vertical cirlce) clamp screw
and sight to object “P” and clamp it
•
Bisect the object “P” accurately with help of
corresponding slow motion screw
•
Read main scales and corresponding vernier scales “C” and
“D”. This angle is called angle of depression.
•
Enter the readings in the proforma
•
Add average of two readings. This reading is the
required vertical angle “POQ”
•
Change the face of the instrument and repeat the process
as explained above
•
Add average of two readings. This reading is the required
angle “POQ”
•
Take average of face left and face right to get
further accurate angle “POQ”
SETTING OUT ANGLE USING THEODOLITE
•
This method is adopted for transferring the angels on
to the ground to establish the required stations or points
Example: Set the angle 30 degrees, 45 minutes and 20
seconds
STEPS:
•
Set the theodolite on the required point from which
the given station or point is to be set
•
Complete the temporary adjustments
•
Bring the verniers “A” to zero and clamp the lower
clamp screw firmly
•
Loosen the upper clamp screw and bring the upper plate
and verniers to angle 30 degrees, 45 minutes and 20 seconds accurately with the
help of corresponding tangent screw
•
Clamp the upper plate firmly
•
Place the desired point in the direction with the help
of telescope and ranging rod.
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