An imaginary line tangential to the longitudinal curve of the bubble tube at its center is called the:

Select the odd option with respect to natural/instrumental sources of error in transit theodolite work.

Which of the following types of leveling is also known as fly leveling?

Which of the following statement(s) about the rise and fall method in levelling is/are correct? Statement I: This method requires calculation of the height of instrument at every station. Statement II: The difference between a back sight and fore sight indicates a rise or fall. Statement III: The method provides an arithmetic check using the sums of back sights, fore sights, rises, and falls.