Define the following terms with regards to theodolite use (6 marks)a) Line of collimationb) Face left conditionc) Plunging the telescoped) Double centering

a) Line of Collimation: This is also known as the line of sight. It is an imaginary line joining the intersection of cross-hairs to the optical center of the object glass and its continuation.

b) Face Left Condition: This is a condition of the theodolite where the telescope is rotated 180 degrees from the face right condition. In this condition, the vertical circle readings increase in the clockwise direction.

c) Plunging the Telescope: This refers to the action of rotating the telescope in its vertical axis. It is done to change the line of sight from an upward to a downward direction or vice versa. This is useful when measuring vertical angles.

d) Double Centering: This is a process used to ensure the accuracy of the theodolite. It involves setting up the theodolite over a survey station, taking measurements, then rotating the instrument 180 degrees and taking the same measurements again. The average of the two sets of measurements is then used, reducing the impact of any instrument errors.