ADJUSTMENT OF A THEODOLITE |Civil Easy Learning

ADJUSTMENT OF A THEODOLITE 

The adjustments of a theodolite are of two kinds :- 

ADJUSTMENT OF A THEODOLITE

1. Permanent Adjustments. 

2. Temporary Adjustments. 

1) Permanent adjustments:

 The permanent adjustments are made to establish the relationship between the fundamental lines of the theodolite and , once made , they last for a long time. They are essential for the accuracy of observations.

1. Permanent adjustments: The permanent adjustments in case of a transit theodolites are :- 

i) Adjustment of Horizontal Plate Levels:

 The axis of the plate levels must be perpendicular to the vertical axis.

ii) Collimation Adjustment:

 The line of collimation should coincide with the axis of the telescope and the axis of the objective slide and should be at right angles to the horizontal axis.

 iii) Horizontal axis adjustment:

 The horizontal axis must be perpendicular to the vertical axis.

iv) Adjustment of Telescope Level or the Altitude Level Plate Levels:

 The axis of the telescope levels or the altitude level must be parallel to the line of collimation. 

v) Vertical Circle Index Adjustment:

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

2. Temporary Adjustment 

The temporary adjustments are made at each set up of the instrument before we start taking observations with the instrument.

 There are three temporary adjustments of a theodolite:- 

i) Centering. 

ii) Levelling. 

iii) Focussing.