Introduction of theodolite and use in surveying


Introduction of theodolite and use in surveying

Introduction of Theodolite

Theodolite is a universal instrument and it is used for the following different purpose in surveying and mines survey.
1. For measuring horizontal angles.
2. For measuring vertical angles.
3. For measuring deflection angles.
4. For measuring magnetic bearings.
5. For measuring the horizontal distance between two points.
6. Finding the vertical height of an object.
7. Finding the difference of elevation between various points.
8. For ranging a line.

Theodolites generally two types. (A) Transit theodolite (B) Non-transit theodolite.
(A) In the transit theodolite, the telescope can be revolved through a complete revolution about its horizontal axis in vertical plan.
(B) In the non-transit theodolite,  the telescope cannot be revolved through a complete revolution in the vertical plane.

Theodolite may also be classified as attachment of angles reading arrangement.
(i) vernier theodolite -In the vernier theodolite, vernier scale fitted for reading angles.
(ii) Micrometre theodolite-In micrometre theodolite micrometre fitted for reading angles.
(iii) Digital theodolite- In the digital theodolite, a digital display fitted for reading angles.

The size of theodolites varies from 8 cm to 25cm. The diameter of the graduated circle of the lower plate defined the size of any theodolite.
Terms used in the operation of theodolite-

A. Centring -It means setting the theodolite exactly over a station. It can be done by plumb bob is suspended from a small hook attached to the underside of the vertical axis of the theodolite.
B. Transiting-The turning the telescope over horizontal axis through 180°in a vertical plane, the telescope brings upside down and making it point exactly in the opposite direction.
C. Face Left-When vertical circle of the instrument is on the left of the observer, the position is called face left when taking a reading.
D. Face right -When the vertical of the instrument is on the right of the observer when the taking reading, this position is called face right.
E. Line of collimation- It is an imaginary line joining the intersection of the cross-hairs of the diaphragm to the optical centre of the object-glass and its continuation.

Image of telescope 🔭   
(1. Object Glass.    2. Ray shade  3. Stops 4. Focusing Screw
       5. Pinion  6. Rack 7. Diaphragm 8. Diaphragm screws 9. Eyepiece. )                                                    E. Axis of telescope - The line the optical centre of the object-glass to the centre of the eyepiece.  
 F. Axis of level tube - The axis of the level tube is the straight line tangential to the longitudinal curve of the level at the centre of the tube.                                                                                                       G. Vertical axis - The axis about which the telescope rotated in a horizontal plane.   
H. Horizontal axis -The axis about which the telescope rotated in a vertical plane.  

Perfect adjustment between the fundamental lines,                                                  

        (i) The axes of the plate levels must be perpendicular to the vertical axis.
      (ii) The line of collimation must be at right to the horizontal axis.             
(iii) The horizontal axis must be perpendicular to the vertical axis.      
             (iv)The axis of the telescope level must be parallel to the line of collimation. 
  (v) The axis of the striding level must be parallel to the horizontal axis.

Digital theodolite has three sections.  
1. Telescope - (i) Objective lens - This lens is used for the nearest the target views. 
                (ii) Eyepiece -This lens is used for the eye end of the telescope. 
                          (iii) Optical line of sight:- It is used for approximate target of a target.
                                     (iv) Telescope focusing ring:- It is used for clear and distinct view of a target.
       2. Standard section:- (i) Vertical clamp is used for locking the telescope in the vertical plane.
                                            (ii) Vertical slow-motion screw is used for exact focusing of the target.
                                        (iii)Battery Cover is used for plugin battery for energy of the instrument.
                        (iv) Vertical circle is used for measuring the vertical angles.
                             (v) Plate level is used for accurate levelling of the instrument.

3. Display panel and operational panel is used to display the reading and operate the instrument. 

Read More:-How to read reading of the theodolite.                                                                                   



Close Menu