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What is the first thing done by the surveyor after setting up the instrument?
releasing all clamps
levelling instrument
turning plates
clamping the plates
levelling instrument
After setting up the tripod and theodolite, the surveyor must perform centering followed immediately by levelling. Levelling ensures the vertical axis of the instrument is perfectly plumb, which is the fundamental prerequisite for accurate angular measurements in both horizontal and vertical planes.
After setting up the tripod and theodolite, the surveyor must perform centering followed immediately by levelling. Levelling ensures the vertical axis of the instrument is perfectly plumb, which is the fundamental prerequisite for accurate angular measurements in both horizontal and vertical planes.
TtotalтАЛ=TcтАЛ+TlтАЛ+TfтАЛ тАФ Total setup time represented as sum of centering, levelling, and focusing times.
The levelling process involves adjusting the foot screws (or levelling screws) to move the bubble of the plate level to the center of its run. This alignment ensures that the horizontal plate is perpendicular to the plumb line (gravity vector), ensuring that subsequent angular readings are not affected by instrumental tilt.
Centering brings the instrument exactly over the station mark using a plumb bob or optical plummet.
Levelling is performed using the foot screws and the plate level (spirit level).
Proper levelling ensures the vertical axis is truly vertical, preventing error in horizontal angle measurement.
The sequence of instrument setup is standard: Centering -> Levelling -> Focusing (CLF).
Minimizes systematic errors in angular observations.
Ensures stable and reliable data for triangulation or traverse surveys.
Time-consuming if the ground is uneven.
Required repeatedly if the tripod is bumped or disturbed.
Traversing in land surveying.
Triangulation for large-scale mapping.
Setting out works in civil construction.
Levelling must be checked at every station to ensure no movement occurred during setup.
Option A is incorrect because releasing clamps is part of the preparation, not the primary stabilization step.
Option C and D relate to the manipulation of plates for measurement, which occurs after the instrument is established.
B is correct тАФ Levelling the instrument is the primary step to define a horizontal datum for angular measurements.
Always remember the acronym 'CLF' (Centering, Levelling, Focusing) for the standard setup sequence in surveying instruments like theodolites and total stations.