Measurement of Vertical Angle by Theodolite

Measurement of Vertical Angle by Theodolite

Measurement of vertical angles is an important operation in theodolite surveying. It is used to determine the angle of elevation or depression of an object. These measurements help in calculating heights and distances. In ITI Draughtsman Civil, understanding the method of measuring vertical angles is essential for accurate surveying work.

1. Definition of Vertical Angle

A vertical angle is the angle between the line of sight and the horizontal plane. It is measured in the vertical plane using the vertical circle of the theodolite.

• Angle of Elevation: When the object is above the horizontal line.
• Angle of Depression: When the object is below the horizontal line.

2. Principle

The vertical angle is measured by rotating the telescope in the vertical plane and reading the angle on the vertical circle of the theodolite.

3. Procedure for Measurement

1. Set up the theodolite over the station point.
2. Perform temporary adjustments (centering, leveling, focusing).
3. Ensure the instrument is properly leveled.
4. Direct the telescope towards the object.
5. Clamp the vertical motion.
6. Use tangent screw for fine adjustment.
7. Read the vertical angle on the vertical circle.
8. Repeat the observation in both Face Left (FL) and Face Right (FR).
9. Take the average value for accuracy.

4. Methods of Measurement

(a) Single Observation Method

• Angle is measured once.
• Suitable for rough work.

(b) Double Observation Method

• Angle is measured in both FL and FR positions.
• Average value is taken.
• Provides higher accuracy.

5. Importance of Vertical Angle Measurement

• Determination of height of buildings, towers, and hills.
• Used in trigonometric leveling.
• Helps in alignment of slopes and gradients.
• Important for construction and design work.

6. Precautions

• Ensure proper leveling of the instrument.
• Avoid parallax by proper focusing.
• Take readings carefully.
• Repeat observations for accuracy.

Role of Draughtsman Civil

A Draughtsman Civil uses vertical angle data to calculate heights and prepare profiles and sections. Accurate measurement ensures correct design and construction.

Conclusion

Measurement of vertical angles is an essential part of theodolite surveying. It helps in determining elevations and heights of objects.

For ITI Draughtsman Civil students, understanding this method is important for accurate surveying and successful engineering applications.