Theodolite is a measurement tool used in surveying to calculate horizontal and vertical angles with the help of a small, mobile low telescope. It is an electronic device used in a triangulation network, which resembles a small telescope. It is widely used in the housing sector and for scaling purposes to measure vertical and horizontal angles. The range of measurement accuracy for these angles is 5 minutes to 0.1 seconds. Read the article to learn about the theodolite survey.
Theodolite survey: What are the types of theodolite?
Transit theodolite
A transit theodolite allows for a full rotation of the telescope installed inside the instrument around its horizontal axis in a vertical plane.
Non-transit theodolite
The telescope in non-transit theodolite cannot rotate 360 degrees around its horizontal axis on a vertical plane. To a certain extent, it can be turned to take vertical angles.
Theodolite category
We can further classify theodolite into two categories based on the scale. The first category is the Vernier Theodolites utilised in routine surveying operations, which are installed on a Vernier scale. The second is the Micrometre Theodolite installed in a Micrometre scale.
Theodolite survey: Size of theodolites
The diameter of a theodolite’s main scale determines its size; for example, a theodolite with a diameter of 10 cm has a main scale with a diameter of 10 cm. 8 cm to 12 cm theodolites are typically employed in surveys.
Theodolite survey: Parts and functions of a theodolite
Telescope
Theodolite’s telescope is fixed to a horizontal spindle. To see the objects, it can be rotated around its horizontal axis. The type of internal focusing used by the telescope means that the objective lens is locked in place and that a second double concave (focusing lens) is moved in front of the objective.
Vertical circle
The vertical circle moves with the telescope and is fastened to it. It is divided into four quadrants, with a reading of 0° to 90° in the appropriate directions in each quadrant. A scale that is typically used to measure vertical angles is also part of the vertical circle.
Plate bubble
On the surface above the Vernier plate, two plate bubbles are mounted at right angles. For the purpose of levelling the theodolite horizontally, one plate bubble is maintained parallel to the instrument’s horizontal axis. Theodolite’s vertical axis is fitted with another plate bubble, which is used to level the instrument vertically.
Clamp screws
To hold the vertical circle and telescope at any desired angle, a vertical clamp screw is used. It stops the telescope from rotating around its horizontal axis. These are often found in the instrument’s lower plate and are used to rotate the device around its horizontal axis.
Trivet
A trivet comprises a circular plate with a threaded hole in the centre that allows the instrument and tripod stand to be securely fixed. The base plate is another name for this plate. Over this plate, the foot screws are fastened using a ball and socket configuration.
Foot screws
Foot Screws are needed to level the instrument in the ground appropriately and are also known as levelling screws.
Tangent screws
Two tangent screws make up the instrument; one is inserted into the lower plate and the other into the upper plate. To precisely bisect the ranging rod that has been put at the spot, the lower tangent screw is used, while the upper tangent screw is meant for a little movement of the scale reading.
Theodolite survey: Uses
Theodolite is used for a variety of tasks, although it is mostly employed for measuring angles and scaling construction work points. For instance, the increasing edges of enormous structures are employed as theodolites to identify highway locations.
Theodolite gives more curved readings, employing paradoxical faces and swings or varied positions for ideal measuring surveys, depending on the nature of the job and the level of accuracy necessary.
Some of the major uses of theodolite survey include:
- Measuring vertical and horizontal angles
- Finding level difference
- Finding points on a line
- Ranging curves
- Tachometric surveying
FAQs
What is the purpose of the theodolite survey?
Theodolite survey is for purposes like measuring vertical and horizontal angles, finding level differences, and finding points on a line.
What are some of the important parts of a theodolite?
Some important parts of a theodolite are a telescope, vertical circle, plate bubble, and clamp screws.
What are the types of theodolite?
The two types of theodolite are transit and non-transit theodolite.
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