Levelling – Types, Components/Parts and Functions
Levelling is an important surveying process used to determine the elevation of different points on the ground. It helps in construction planning, road alignment, and drainage design. In ITI Draughtsman Civil, students must understand the types of levelling, the components of levelling instruments, and their functions for accurate fieldwork.
1. Types of Levelling
Levelling can be classified into different types based on the method and purpose of work.
(a) Simple Levelling
- Used to find the difference in elevation between two points.
- Suitable for short distances.
(b) Differential Levelling
- Used when points are far apart or obstacles exist.
- Involves multiple instrument setups.
(c) Fly Levelling
- Used to transfer benchmark from one location to another.
- Quick method without taking detailed observations.
(d) Profile Levelling
- Used for preparing longitudinal sections.
- Commonly used in roads and canals.
(e) Cross Section Levelling
- Used to determine levels across a line.
- Helpful in earthwork calculations.
(f) Reciprocal Levelling
- Used to overcome errors due to obstacles like rivers.
- Provides more accurate results.
2. Components/Parts of Levelling Instrument
A levelling instrument (such as auto level or dumpy level) consists of several important parts:
- Telescope: Used to sight the levelling staff and take readings.
- Eyepiece: Used to view the staff image clearly.
- Objective Lens: Collects light from the staff.
- Focusing Screw: Adjusts clarity of the image.
- Level Tube (Spirit Level): Ensures the instrument is horizontal.
- Levelling Screws: Used for fine adjustment and leveling.
- Base Plate: Supports the instrument.
- Tripod Stand: Holds the instrument steady.
3. Functions of Components
Each part of the levelling instrument has a specific function:
- Telescope: Provides a clear line of sight for measurement.
- Eyepiece: Helps in focusing the cross hairs.
- Objective Lens: Forms an image of the staff.
- Focusing Screw: Adjusts sharpness of the image.
- Spirit Level: Ensures horizontal alignment.
- Levelling Screws: Used to level the instrument.
- Tripod: Provides stability and support.
4. Importance of Understanding Components
- Helps in proper handling of the instrument.
- Ensures accurate levelling work.
- Reduces chances of errors.
- Improves efficiency in field operations.
5. Precautions
- Ensure proper leveling before taking readings.
- Keep the instrument clean and protected.
- Handle the telescope carefully.
- Check adjustments regularly.
Role of Draughtsman Civil
A Draughtsman Civil uses levelling data to prepare profiles, sections, and contour maps. Understanding types, components, and functions helps in accurate data collection and drawing preparation.
Conclusion
Levelling is an essential surveying process with various types used for different purposes. The levelling instrument consists of several components, each performing a specific function.
For ITI Draughtsman Civil students, knowledge of levelling types, components, and their functions is important for accurate surveying and successful construction work.