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The vertical circle is a circular graduated arc attached to the ______ axis of the telescope.
Vertical Axis
Outer Axis
Trunnion Axis
Line of sight
Trunnion Axis
The vertical circle is a graduated circular plate rigidly attached to the trunnion axis (also called the horizontal axis) of a theodolite ┬╖ This arrangement ensures that the vertical circle rotates along with the telescope when it is moved in the vertical plane, allowing for the measurement of vertical angles.
The vertical circle is a graduated circular plate rigidly attached to the trunnion axis (also called the horizontal axis) of a theodolite ┬╖ This arrangement ensures that the vertical circle rotates along with the telescope when it is moved in the vertical plane, allowing for the measurement of vertical angles.
V=RfтАЛтИТRiтАЛ тАФ represents the vertical angle calculation as the difference between final and initial circle readings
The trunnion axis serves as the pivot around which the telescope transits ┬╖ Because the vertical circle is fixed directly to this axis, any angular displacement of the telescope in the altitude plane corresponds directly to the rotation of the vertical circle relative to the vernier or optical reading system, enabling accurate vertical angle determination.
The trunnion axis is perpendicular to the vertical axis of the theodolite.
The vertical circle must be adjusted to be perfectly centered on the trunnion axis to avoid eccentricity errors.
Vertical angles are measured from the horizontal plane, typically ranging from 0┬░ to 90┬░ in all four quadrants.
Direct measurement of vertical angles with high precision.
Essential for trigonometric leveling and slope staking.
Susceptible to index error if the vertical circle is not perfectly leveled.
Requires periodic calibration to maintain accuracy.
Topographic surveying
Trigonometric leveling
Setting out grades in construction
The Vertical Axis is the primary axis of rotation for the instrument in the horizontal plane.
The Line of Sight (or Line of Collimation) passes through the center of the objective lens and the intersection of the crosshairs.
Option A is incorrect because the vertical axis is for horizontal rotation; the vertical circle remains stationary relative to the telescope during horizontal rotation.
C is correct тАФ The vertical circle is rigidly attached to the trunnion axis, which acts as the horizontal pivot point for the telescope.
Always remember that the Trunnion axis is the horizontal axis; confusing it with the vertical (azimuth) axis is a common source of error in exam questions.