Short Answer:

Theodolites are surveying instruments used to measure horizontal and vertical angles. There are mainly two types of theodolites: Vernier theodolite and Digital theodolite. Vernier theodolites are manual and use vernier scales for reading angles, while digital theodolites show angle readings directly on a screen.

Besides these, based on function and structure, theodolites are also classified as repeating theodolites, transit theodolites, and non-transit theodolites. Each type serves different levels of precision and ease in angle measurement tasks in surveying and construction projects.

Detailed Explanation:

Types of theodolites

Theodolites are important instruments in civil engineering, mainly used for measuring angles in the field. These instruments have developed over time, and now different types are available to suit different needs. Understanding the types of theodolites helps in choosing the right one for accurate angle measurement in various surveying works.

1. Vernier theodolite

This is the traditional and manual type of theodolite. It uses vernier scales to measure angles. It has graduated circles on which the angles are marked, and the surveyor reads the values using the vernier. These theodolites require more skill to operate and take more time to measure and record angles. However, they are still used where electricity or batteries are not available.

2. Digital theodolite

This is a modern version of theodolite. It displays angle readings digitally on a small screen. It is easy to use, faster, and more accurate than the manual type. Digital theodolites reduce the chances of human reading error and are commonly used in modern construction and engineering works.

3. Transit theodolite

In this type, the telescope can rotate completely in the vertical plane. This means the telescope can be turned around and used for both forward and backward readings. Transit theodolites are very flexible and allow multiple angle observations. Most modern theodolites are of this type.

4. Non-transit theodolite

This is an older version where the telescope cannot be rotated fully in the vertical plane. It can only be tilted to a limited angle. This type is rarely used now because of limited flexibility.

5. Repeating theodolite

This type is designed to measure the same angle multiple times and then take the average of those readings. This helps in increasing the accuracy of the measurement. It is useful when very precise angle readings are required, such as in geodetic surveys.

Each type of theodolite has its own advantages and is chosen based on the kind of work, location, and accuracy required. For example, a digital theodolite is perfect for building construction due to its ease of use, while a repeating theodolite is better suited for high-precision work like large area mapping or boundary marking.

The selection of theodolite also depends on the site conditions. In remote areas with no power supply, manual theodolites are still helpful. In contrast, on modern construction sites, digital types are preferred due to their speed and data storage features.

Conclusion

Theodolites are divided into different types based on design and usage. Main types include Vernier, Digital, Transit, Non-Transit, and Repeating theodolites. Each serves specific surveying needs, from basic fieldwork to high-accuracy engineering projects. Choosing the correct type ensures better measurement and quality work.