Component parts of Theodolite with explanation of each part and functions

                                           THEODOLITE

           OBJECTIVE: The main objective of theodolite is to measure both the horizontal and vertical angles.

*Based on transiting theodolites are of two types:
 1.Transit surveying
 2.Non-Transit surveying

NOTE: Transiting mean rotating,as theodolite can be rotated in horizontal and vertical planes it is called transit theodolite.And which can be used only to measure horizontal angles it is called non-transit theodolite.


COMPONENTS PARTS OF THEODOLITE:

PARTS OF THEODOLITE

1.HORIZONTAL ANGLE;Measured with horizontal scale of vernier A&B.Horizontal angle measures from (0-360)°.vernier A&B is attached to upper plate A&B.
 Mainscale-least count __20',0°,0'{20minutes}        
 Vernier scale-least count__20",0',0"{20seconds} 

2.VERTICAL ANGLE:Measured with vertical scale of vernier C&D.It ranges from(0-90)° 

3.UPPER CLAMP AND LOWER CLAMP:

• When upper clamp screw is tightened,but lower clamp screw then verneir scale readings don't change and we can measure main scale readings.

• When lower clamp is tightened,but upper clamp is loose than we can measure vernier scale readings.

4.FACE LEFT CONDITION :

• If the vertical circle left side on the observer than the theodolite is in face left condition 
• In this condition telescope is normal,bubble is upwards.

5.FACE RIGHT CONDITION:

• If the vertical circle is right side to the observer than the theodolite is in face right condition 

• Tn this condition telescope is inverted,bubble is downwards 

6.SWING TELESCOPE:

• It is the process of turning the telescope in horizontal plane about vertical axis.

• Rotation of telescope in clockwise direction is called right swing.

• Rotation of telescope in anti-clockwise  is called left swing. 

NOTE: Face left condition with right swing is best combination.

7.TRANSITING THE TELESCOPE:

• It is the process of rotating the telescope of theodolite  in vertical plane about horizontal axis that is rotating in y-direction about to the X-axis is called transiting the telescope
• It is also known as reversing or plunging.

8.Double sighting or Double entering:

• double sighting is the way to measure horizontal and vertical angles in face left and face right condition.
• In an technical way it is the process of measurement of horizontal and vertical angles in both the conditions(FL&FR).

9.HORIZONTAL AXIS:

• It is also known as transverse or elevation axis.
• It is the plane of rotation of a telescope in vertical plane. 

10.VERTICAL AXIS:

• It is axis of rotation of the telescope in the horizontal plane.

ERRORS IN THEODOLITE:

1.Instrumental error: These type of error occur due to construction defects or either due to the permanent adjustments.

2.Personal error: personal error occur due to the instrument not leveled properly or due to the sighting the measurements or note down the readings.

3.Errors due to natural causes: 

• Observations and setting out angles shouldn't be taken in windy conditions.
• Instrument must be left to adjust to atmosphere  conditions.
• If refraction is a problem than reading must not be taken.
• The instrument must be kept in shade while working in hot sunshine.
• Setting out up the instrument on the soft ground must be avoided.