THEODOLITE AND ITS IMPORTANT TERMS :- -
(for SURVEYING QUIZ.,go down)
THEODOLITE :-
The Theodolite is the most precise instrument designed for the measurement of horizontal , vertical angles and has wide applicability in surveying such as laying of horizontal angles, locating points on line, prolonging survey lines, establishing grades, determining difference in elevation, setting out curves etc.
Theodolites may be classified as:-
(1) Transit theodolite.
(2) Non-transit theodolite
A transit theodolite (or simply 'transit) is one is which the line of sight can be reversed by revolving the telescope through 180° in the vertical plane. The non-transit theodolite either plain theodolite or Y-theodolite in which the telescope cannot be transited. The transit is mainly used and non-transit theodolite have now become obsolete.
ITS COMPONENTS PARTS....
How Does a Theodolite Work?
A theodolite works by combining optical plummets (or plumb bobs), a spirit (bubble level), and graduated circles to find vertical and horizontal angles in surveying. An optical plummet ensures the theodolite is placed as close to exactly vertical above the survey point. The internal spirit level makes sure the device is level to to the horizon. The graduated circles, one vertical and one horizontal, allow the user to actually survey for angles.
DEFINITIONS AND TERMS : -
(1) The vertical axis:- The vertical axis is the axis about which instrument can be rotated in a horizontal plane. This is the axis about which the lower and upper plates rotate.
2) The horizontal axis. :-
The horizontal or trunnion axis is the axis which the telescope and the vertical circle rotate in vertical plane.
(3) The line of sight or line of collimation.:-
It is the line passing through intersection of the horizontal and vertical cross-hairs and the optical center of the object glass and its continuation.
(4) the axis of level tube:-
The axis of the level tube or the bubble line is a straight line tangential to the rectangular curve of the level tube at its center. The axis of the level-tube is horizontal when the bubble is central .
(5) Centring :-
The process of setting the theodolite is exactly over the station mark is known as centering.
(6) Transiting.:-
It is the process of turning the telescope in vertical plane through 180 ° about the trunnion axis. Since the line of sight is reversed in this operation, it is also known as plunging or reversing .
(7) Swinging the telescope :-
It is the process of turning the telescope in horizontal plane. If the telescope is rotated in clock-wise direction, it is known as right swing. If telescope is rotated in the anti-clockwise direction, it is known as the left swing.
(8) Face left observation.:-
If the vertical circle is the left of the observer, the observation of the angle (horizontal or vertical) is called face left observation.
(9) Face right observation:-
If the face of the vertical circle is the right of the observer The vertical circle is to the observer the observation is know as face right observation.
(10) Telescope normal:-
A telescope is said to be normal or direct when the face of the vertical circle is to the left and "the bobble ( of the telescope) up " .
(11) Telescope inverted.:-
A telescope is said to inverted or reversed when the vertical circle is to the right and" bobble down ".
(12) Changing face.:-
It is an operation of bringing the face of the telescope from left to right and Vise versa.
Advantages of Using a Theodolite:-
Theodolites have many advantages when compared to other leveling instruments:
- Greater accuracy.
- Internal magnifying optical system.
- Electronic readings.
- Horizontal circles can be instantly zeroed or set to any other value.
- Horizontal circle readings can be taken either to the left or right of zero.
- Repeat readings are unnecessary.
Thanks you. 😃
Now its QUIZ TIME
Now its QUIZ TIME
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