Surveying – Introduction and Basic Concepts
Surveying is one of the most important subjects in civil engineering and plays a vital role in planning, designing, and construction of engineering projects. In ITI Draughtsman Civil, the study of surveying helps students understand how to measure distances, angles, and elevations on the earth’s surface and represent them accurately on drawings and maps.
Surveying is defined as the science and art of determining the relative positions of points on, above, or below the surface of the earth. These positions are represented in the form of maps, plans, and drawings. It is essential for construction of roads, buildings, bridges, dams, railways, and other infrastructure projects.
1. Objectives of Surveying
The main objective of surveying is to prepare accurate plans and maps for engineering works. It provides necessary data for planning and execution of construction projects.
- To determine the relative position of points on the ground.
- To prepare maps and plans of an area.
- To calculate areas and volumes of land.
- To set out positions for construction work.
- To establish boundaries of land and properties.
2. Principles of Surveying
Surveying is based on two fundamental principles:
- Working from Whole to Part: First, a large area is surveyed with high accuracy, and then smaller parts are measured. This reduces errors.
- Fixing Points by Two Measurements: The position of a point is fixed by taking at least two measurements from known points.
3. Types of Surveying
Surveying is classified into different types based on the nature and purpose of work.
(a) Plane Surveying
- Assumes the earth surface as flat.
- Used for small areas.
- Suitable for ordinary engineering projects.
(b) Geodetic Surveying
- Considers the curvature of the earth.
- Used for large areas.
- Highly accurate and complex.
(c) Based on Method
- Chain Survey
- Compass Survey
- Plane Table Survey
- Theodolite Survey
- Levelling
4. Chain Survey
Chain surveying is the simplest method of surveying in which only linear measurements are taken. It is suitable for small, flat areas.
- Uses chain or tape for measurement.
- Forms a network of triangles.
- Easy to use and economical.
5. Compass Survey
Compass surveying is used to measure both distances and angles. A magnetic compass is used to determine directions.
- Measures bearings of survey lines.
- Suitable for large areas.
- Affected by magnetic disturbances.
6. Levelling
Levelling is the process of determining the height of points relative to a reference level. It is used to prepare contour maps and for construction works.
- Uses levelling instrument and staff.
- Important for drainage and road construction.
7. Instruments Used in Surveying
Various instruments are used in surveying to measure distances, angles, and elevations.
- Chain and Tape: For linear measurement.
- Compass: For measuring directions.
- Plane Table: For direct plotting.
- Theodolite: For precise angle measurement.
- Level: For measuring elevations.
- Staff: Used with levelling instrument.
8. Uses of Surveying
- Preparation of maps and plans.
- Construction of roads, railways, and buildings.
- Determination of land boundaries.
- Calculation of earthwork quantities.
- Planning of irrigation and drainage systems.
9. Importance of Surveying
Surveying is the foundation of all civil engineering works. Without proper surveying, it is impossible to design and execute construction projects accurately.
- Ensures accuracy in construction.
- Helps in proper planning and design.
- Reduces errors and construction costs.
- Provides essential data for engineers and architects.
Role of Draughtsman Civil
A Draughtsman Civil uses survey data to prepare detailed drawings and plans. They convert field measurements into graphical representations, ensuring accuracy in construction layouts.
Conclusion
Surveying is an essential subject for ITI Draughtsman Civil students. It involves measurement, mapping, and representation of land features. Understanding basic concepts such as objectives, principles, types, and instruments helps students perform accurate surveying work.
With proper knowledge of surveying, students can contribute effectively to planning and execution of engineering projects, ensuring safe and efficient construction.