Field Procedure of Chain Survey, Errors in Chain Survey and Plotting Procedure

Chain surveying is one of the simplest and most commonly used methods in surveying. It involves only linear measurements and is suitable for small areas with simple details. To achieve accurate results, it is important to follow a systematic field procedure, understand possible errors, and apply proper plotting techniques. These aspects are essential for students in the Surveyor trade.

Field Procedure of Chain Survey

The field procedure of chain surveying involves several steps that must be carried out carefully and systematically:

1. Reconnaissance

Reconnaissance is the initial inspection of the survey area. The surveyor studies the area, identifies important features, and decides the positions of survey stations and main lines.

2. Selection of Stations

Survey stations are selected at suitable points so that the entire area can be covered by a network of triangles. Stations should be intervisible and well-defined.

3. Marking of Stations

Stations are marked on the ground using pegs, nails, or ranging rods. Proper marking ensures accurate measurement and easy identification.

4. Ranging of Lines

Ranging is done to establish straight lines between stations. Intermediate points are fixed using ranging rods to maintain alignment.

5. Measurement of Distances

Distances between stations are measured using a chain or tape. Measurements should be taken carefully to avoid errors.

6. Taking Offsets

Offsets are taken to locate details such as buildings, roads, and trees. These are measured from the survey line.

7. Recording in Field Book

All measurements and observations are recorded in the field book systematically. Proper recording is essential for accurate plotting.

8. Checking of Work

Check lines or tie lines are measured to verify the accuracy of the survey. Any discrepancies should be corrected immediately.

Errors in Chain Survey

Errors are unavoidable in any measurement process. In chain surveying, errors may occur due to various reasons and can affect the accuracy of the results.

Types of Errors

1. Instrumental Errors

These errors occur due to defects in the chain or tape, such as incorrect length, wear and tear, or damage.

2. Personal Errors

These errors are caused by human mistakes, such as неправиль alignment, неправиль reading, or неправиль recording.

3. Natural Errors

These errors occur due to environmental factors such as temperature, wind, slope, and sag of the chain.

Common Errors in Chain Survey

• Incorrect length of chain
• Poor ranging and alignment
• Incorrect measurement of offsets
• Sagging of chain
• Measurement on sloping ground without correction
• Errors in field book recording

Minimization of Errors

• Test and adjust the chain regularly
• Ensure proper alignment during ranging
• Use suitable methods for sloping ground
• Maintain proper tension in chain
• Record data carefully in field book
• Use check lines to verify measurements

Plotting Procedure

Plotting is the process of representing field measurements on a drawing sheet. It converts field data into a map or plan.

Steps in Plotting

1. Selection of Scale

Choose a suitable scale based on the size of the area and the level of detail required.

2. Drawing of Framework

Plot the main survey lines and stations on the drawing sheet using measured distances.

3. Plotting of Offsets

Offsets are plotted from the survey lines to locate details. Perpendicular or oblique methods are used as per field data.

4. Joining of Points

Join the plotted points to represent features such as buildings, roads, and boundaries.

5. Use of Conventional Symbols

Standard symbols are used to represent different features for clarity and uniformity.

6. Checking and Finishing

The drawing is checked for accuracy and completeness. Title block, scale, and legend are added.

Precautions in Plotting

• Use accurate scale and instruments
• Maintain neatness and clarity
• Avoid overcrowding of details
• Double-check all measurements
• Use standard symbols and lettering

Importance in Surveyor Trade

Understanding the field procedure, errors, and plotting techniques is essential for surveyor trainees. Accurate fieldwork combined with proper plotting ensures reliable results.

These skills are fundamental for preparing maps and plans used in construction and development projects.

Conclusion

Chain surveying involves systematic field procedures, careful measurement, and accurate plotting. Errors may occur during surveying, but they can be minimized by following proper methods and precautions.

Plotting converts field data into useful drawings, making it an important step in surveying. For ITI Surveyor trainees, mastering these concepts is essential for developing professional skills and ensuring accuracy in their work.