Theodolite Survey
Theodolite surveying is an advanced method of surveying used for precise measurement of horizontal and vertical angles. It is widely used in engineering projects such as road construction, bridge alignment, and building layout. In ITI Draughtsman Civil, understanding theodolite survey is essential for accurate fieldwork and preparation of detailed drawings.
1. Introduction to Theodolite Survey
A theodolite is a precision instrument used to measure angles in both horizontal and vertical planes. Unlike compass surveying, which measures only directions, theodolite surveying provides highly accurate angular measurements.
It is commonly used in triangulation, traversing, and alignment of engineering structures.
2. Definition of Theodolite
A theodolite is an optical instrument used for measuring horizontal and vertical angles with high precision in surveying.
3. Types of Theodolite
- Transit Theodolite: Telescope can be rotated fully in vertical plane.
- Non-Transit Theodolite: Telescope cannot be fully rotated.
- Digital Theodolite: Provides electronic display of readings.
4. Parts of Theodolite
- Telescope: Used for sighting objects.
- Eyepiece and Objective Lens: For viewing and focusing.
- Horizontal Circle: Measures horizontal angles.
- Vertical Circle: Measures vertical angles.
- Levelling Screws: Used for leveling the instrument.
- Tripod Stand: Supports the instrument.
- Plumb Bob: Used for centering.
5. Temporary Adjustments of Theodolite
- Setting Up: Fix the instrument on tripod.
- Centering: Place instrument exactly over the station point.
- Levelling: Use levelling screws to make instrument horizontal.
- Focusing: Adjust eyepiece and objective for clear image.
6. Measurement of Angles
(a) Horizontal Angle Measurement
- Set the instrument over a station.
- Take readings for two points.
- Calculate the angle between them.
(b) Vertical Angle Measurement
- Measure angle above or below horizontal line.
- Used for height and distance calculations.
7. Applications of Theodolite Survey
- Triangulation and traversing.
- Setting out of buildings and roads.
- Alignment of tunnels and bridges.
- Measurement of heights and distances.
8. Advantages of Theodolite Survey
- High accuracy and precision.
- Measures both horizontal and vertical angles.
- Suitable for large and complex projects.
9. Disadvantages of Theodolite Survey
- Requires skilled operation.
- Time-consuming compared to simple methods.
- Costlier equipment.
10. Precautions
- Ensure proper leveling and centering.
- Handle instrument carefully.
- Take accurate readings.
- Avoid disturbances during observation.
Role of Draughtsman Civil
A Draughtsman Civil uses data obtained from theodolite survey to prepare accurate layouts, plans, and construction drawings. It helps in precise alignment and design of engineering structures.
Conclusion
Theodolite surveying is a precise and reliable method used for measuring angles in surveying. It is widely used in civil engineering projects for accurate layout and construction.
For ITI Draughtsman Civil students, understanding theodolite survey is essential for developing advanced surveying skills and ensuring successful project execution.