Introduction to Theodolite, Surveying and Levelling | Surveying and Levelling Notes- Agricultural Engg - Agricultural Engineering PDF Download

Uses of Theodolite
     i) Measurement of Horizontal and vertical angles.
     ii) Setting out lines and angles
     iii) Optical distance measurement
     iv) Plumbing tall building
     v) Setting out of Railway curves
    vi) Locating the position of piers for Bridge etc.
   vii) Geographical position fixing from observation of sun and stars.
   viii) Alignment control in tunnel construction.

CLASSIFICATION
Theodolite may be classified into transit and non-transit theodolites.

1. Transit theodolite
   • A theodolite is said to be transit one when its telescope can be revolved through 180° in a vertical plane about its horizontal axis, thus directing the telescope in exactly opposite direction.
2.  Non-transit theodolite
   • A theodolite is said to be a non-transit one when its telescope cannot be revolved through 180° in a vertical plane about its horizontal axis.

IMPORTANT DEFINITIONS –
i) Line of Collimation  -  the line which passes through the Intersection of the cross hairs of the eye piece and optical centre of the objective and its continuation is called as line of collimation.  This is also known as line of sight.

ii) Transiting -  The process of turning the telescope in vertical plane through 180 deg. about its horizontal axis is known as transiting.

iii) Swing -  A continuous motion of telescope about the vertical axis in horizontal plane is called swing.  The swing may be in either direction i.e. Right swing or left swing.

iv) Face left observation – When vertical circle is on the left of the telescope at the time of observation, the observations are called face left observation.

v) Face right observation – When vertical circle is on the right of the telescope at the time of observation.