Surveying
To avoid large centering error with very short legs, observations are generally made

All listed here
By using optical system for centering the theodolite
To a target fixed on theodolite tripod on which theodolite may be fitted easily
To chain pins

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Surveying
Refraction correction

partially eliminates curvature correction
adds to the curvature correction
completely eliminates curvature correction
has no effect on curvature correction

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Surveying
The length of a chain is measured from

inside of one handle to inside of other handle
outside of one handle to inside of other handle
outside of one handle to outside of other handle
centre of one handle to centre of other handle

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Surveying
Theodolite is an instrument used for

tightening the capstan-headed nuts of level tube
measurement of horizontal angles only
measurement of both horizontal and vertical angles
measurement of vertical angles only

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