Chain Survey – Introduction, History and Principles
Chain surveying is one of the oldest and simplest methods of land surveying. It is widely used for measuring small areas with simple details. In ITI Draughtsman Civil, the study of chain surveying helps students understand basic field measurement techniques and preparation of plans.
1. Introduction to Chain Survey
Chain surveying is a method of surveying in which only linear measurements are taken in the field using a chain or tape. No angular measurements are required. The area to be surveyed is divided into a network of triangles, which ensures accuracy and simplicity.
This method is suitable for small and fairly level areas with simple features such as fields, playgrounds, and small plots. It is not suitable for large or uneven areas with many obstacles.
Features of Chain Survey
- Only linear measurements are taken.
- Uses chain or tape for measurement.
- Forms a framework of triangles.
- Simple and economical method.
2. History of Chain Survey
The concept of chain surveying dates back to ancient times when land measurement was required for agriculture and construction. Early civilizations such as Egyptians and Romans used ropes and simple tools for measuring land.
The modern chain surveying method developed with the invention of the surveyor’s chain, commonly known as Gunter’s chain, in the 17th century. This chain was widely used in land measurement and mapping.
Over time, improvements in tools and techniques have made surveying more accurate and efficient. Although advanced instruments are now available, chain surveying remains an important basic method for learning and small-scale surveys.
3. Principles of Chain Survey
Chain surveying is based on simple geometric principles, mainly the use of triangles. The following are the fundamental principles:
(a) Principle of Triangulation
- The area is divided into a network of well-conditioned triangles.
- Triangles are preferred because they are stable and can be easily measured.
- Accurate measurement of sides ensures correct plotting.
(b) Working from Whole to Part
- The entire area is first divided into large triangles.
- Smaller details are then measured within these triangles.
- This method reduces accumulation of errors.
(c) Fixing Points by Linear Measurements
- Points are fixed by measuring distances from known points.
- No angular measurements are required.
(d) Use of Check Lines
- Check lines are used to verify the accuracy of measurements.
- They help in detecting errors in the survey work.
4. Types of Lines in Chain Survey
- Main Survey Lines: Lines forming the main framework.
- Base Line: The longest and most important line in the survey.
- Tie Lines: Lines used to locate interior details.
- Check Lines: Lines used to check accuracy.
5. Advantages of Chain Survey
- Simple and easy to understand.
- Requires minimum equipment.
- Economical for small areas.
- Suitable for beginners.
6. Limitations of Chain Survey
- Not suitable for large or uneven areas.
- Cannot be used in areas with many obstacles.
- Less accurate compared to modern methods.
Role of Draughtsman Civil
A Draughtsman Civil uses data obtained from chain surveying to prepare accurate site plans and layouts. Understanding basic principles helps in converting field measurements into graphical representations.
Conclusion
Chain surveying is a fundamental method in surveying that uses simple tools and principles for measuring land. It is based on triangulation and linear measurements, making it easy to learn and apply.
For ITI Draughtsman Civil students, knowledge of chain survey introduction, history, and principles is essential for building a strong foundation in surveying practices.