Precautions in Using Prismatic Compass
The prismatic compass is an important instrument used in compass surveying for measuring bearings of survey lines. To obtain accurate results, it is essential to handle and use the compass carefully. In ITI Draughtsman Civil, students must follow proper precautions while using a prismatic compass to avoid errors in measurement.
1. General Precautions
- Handle the compass carefully to avoid damage.
- Do not drop or shake the instrument.
- Keep the glass cover clean and free from dust.
- Ensure the magnetic needle moves freely.
2. Precautions During Setup
- Place the compass on a stable tripod or hold it firmly.
- Ensure proper centering over the survey station.
- Level the instrument properly for accurate readings.
- Allow the needle to come to rest before taking readings.
3. Avoiding Magnetic Interference
Magnetic disturbances can affect the accuracy of compass readings. Therefore, the following precautions must be taken:
- Keep the compass away from iron and steel objects.
- Avoid working near electric poles, cables, or machinery.
- Do not carry metallic objects close to the compass.
4. Precautions During Observation
- Take readings only after the needle has settled.
- Ensure correct alignment of object vane and eye vane.
- Read the bearing carefully through the prism.
- Avoid parallax error while reading the scale.
5. Recording Precautions
- Record readings immediately in the field book.
- Double-check the recorded values.
- Note down any abnormal observations.
6. Maintenance Precautions
- Clean the instrument after use.
- Store the compass in a dry and safe place.
- Protect it from moisture and rust.
- Check for any damage before use.
7. Importance of Precautions
- Ensures accurate measurement of bearings.
- Reduces errors due to external factors.
- Increases the life of the instrument.
- Improves reliability of survey data.
Role of Draughtsman Civil
A Draughtsman Civil uses compass survey data for preparing plans and layouts. Proper precautions while using the prismatic compass ensure accurate data, which leads to correct drawings and designs.
Conclusion
The prismatic compass is a sensitive instrument that requires careful handling and proper use. Following necessary precautions helps in obtaining accurate readings and avoiding errors.
For ITI Draughtsman Civil students, understanding and applying these precautions is essential for successful surveying work.