FUNDAMENTALS OF SURVEYING : Fundamental lines and desired relations

Fundamental lines and desired relations:

1) Vertical axis                                                     2) Horizontal axis or trunion axis or transit axis,

1)   line of collimation or line of sight                   4) Axis of plate level
5) Axis of altitude level,

For the proper adjustment or accurate adjustment ofthe theodolite following relations between fundamental lines are desired,

1)      Line of collimation must be perpendicular to the horizontal axis at its intersection.

2)      Axis of the plate level must be perpendicular to vertical axis.

3)      Horizontal axis must be perpendicular to vertical axis.

4)      Axis of altitude level or telescope level must be parallel to line of collimation.

5)      The vertical circle vernier must read zero when the line of collimation is horizontal.

Striding level axis must be parallel to horizontal axis.