What are the instrumental errors of theodolite?

The instrumental errors are the type of errors that arise on account of the defect or malfunction of the theodolite itself. When the plate levels of the theodolite are not perpendicular to the vertical axis, the vertical axis is not perfectly vertical which results in the inclination of the horizontal circle.

What are the different errors in theodolite work how are they eliminated?

The error can be eliminated by taking the mean of the two observed values of the angle, one with the telescope normal and the other with the telescope inverted. If the centre of the graduated circle plate does not coincide with the centre of the vernier plate, the angle recorded by either of the verniers is incorrect.

What is an index error in theodolite?

Index error. The angles in the vertical axis should read 90° (100 grad) when the sight axis is horizontal, or 270° (300 grad) when the instrument is transited. Half of the difference between the two positions is called the index error.

How many theodolite is there?

There are two different kinds of theodolites: digital and non digital. Non digital theodolites are rarely used anymore. Digital theodolites consist of a telescope that is mounted on a base, as well as an electronic readout screen that is used to display horizontal and vertical angles.

What is parallax error in theodolite?

Parallax error occurs when the measurement of an object’s length is more or less than the true length because of your eye being positioned at an angle to the measurement markings. … A wider edge allows for a larger parallax error because the object could be higher or lower with respect to the true measurement marking.

How many methods are in theodolite surveying?

Measurement of Horizontal Angles: Top 3 Methods | Theodolite Surveying | Surveying. Article shared by : ADVERTISEMENTS: There are three methods of measuring horizontal angles: 1.

What are the various types of theodolite?

Theodolites generally include three types.
  • Repeating Theodolite. Repeating theodolites refer to those theodolites which measure angles on a graduated scale. …
  • Direction Theodolites. Direction theodolites refer to those theodolites which determine angles through a circle. …
  • Vernier Transit Theodolite. …
  • Solved Question For You.

What are two types of theodolite?

Types of Theodolite
  • Repeating Theodolite.
  • Directional Theodolite.
  • Electrical Digital Theodolite.
  • Total Station.

How many vernier scales are there in a theodolite?

a) Vernier Theodolite:- These theodolites use verniers to take readings and are most commonly used. The upper plate of a transit theodolite has two verniers which are diametrically opposite to each other. If this plate is unclamped the upper plate rotates and the reading of the vernier changes.

How many vernier scales are there in theodolite?

For the vernier, 59 main scale divisions are taken and divided into 60 parts.

What is theodolite survey?

theodolite, basic surveying instrument of unknown origin but going back to the 16th-century English mathematician Leonard Digges; it is used to measure horizontal and vertical angles. In its modern form it consists of a telescope mounted to swivel both horizontally and vertically.

Which vernier is used in theodolite?

Vernier Theodolite: For reading the graduated circle if verniers are used ,the theodolite is called as a Vernier Theodolite. Whereas, if a micrometer is provided to read the graduated circle the same is called as a Micrometer Theodolite. Vernier type theodolites are commonly used .

How many bubble tubes are in theodolite?

The Transit Theodolite Plate Bubble • Two plate bubbles are mounted at right angles to each other on the upper surface of the vernier plate. One bubble is kept right parallel to the horizontal axis of the theodolite. Sometimes one plate bubble is provided on the vernier plate.

How accurate is a theodolite?

A number of investigators reported results of similar tests using theodolites, not levels. For distances less than 150 m, almost all investigators reported accuracy values in the range from 1/600 to 1/2100.