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Which one of the following statement is CORRECT?
- a)In levelling, if backsight is less than foresight, the back sight stations lower than the foresight station.
- b)In reciprocal levelling, the error due to refraction is not eliminated.
- c)At a change point in levelling, two backsight are taken.
- d)The effect of curvature is to cause the objects sighted to appear lower than they really are.
Correct answer is option 'D'. Can you explain this answer?
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Which one of the following statement is CORRECT?a)In levelling, if bac...
In levelling, if backsight is less than foresight, then backsight station is at higher than foresight station. In reciprocal levelling, the error due to refraction, curvature is eliminated. At change point in levelling one backsight and one foresight are taken.
Due to the effect of curvature, the object is sighted to appear lower than they really are.
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Which one of the following statement is CORRECT?a)In levelling, if bac...
Correct Answer: D) The effect of curvature is to cause the objects sighted to appear lower than they really are.
Explanation:
In levelling, the curvature of the Earth is one of the sources of error that needs to be considered. The effect of curvature is to cause the objects sighted to appear lower than they really are. This is because when we sight an object, we are effectively looking along a tangent line to the Earth's surface, and as we move away from the object, the line of sight becomes more and more parallel to the tangent line. This means that the line of sight does not follow the curve of the Earth, causing the object to appear lower.
Effects of Curvature in Levelling:
The effect of curvature can be significant in levelling, especially when measuring over long distances. This is because the curvature of the Earth causes the line of sight to deviate from the horizontal plane. As a result, the measured elevation of a point will be lower than the true elevation.
Compensating for Curvature:
To compensate for the curvature of the Earth, corrections need to be applied to the measured elevations. One common method is to use a correction factor called the curvature correction. The curvature correction is calculated based on the distance between the instrument and the target point. By subtracting the curvature correction from the measured elevation, the true elevation can be determined.
Other Sources of Error in Levelling:
While the effect of curvature is one source of error in levelling, there are other sources of error that also need to be considered. These include:
- Atmospheric refraction: The bending of light rays as they pass through the Earth's atmosphere can cause errors in levelling measurements. In reciprocal levelling, the error due to refraction is eliminated by taking a foresight and a backsight from each instrument station.
- Instrument errors: Levelling instruments can have inherent errors that need to be taken into account. These errors can include misalignment of the telescope, imperfect leveling of the instrument, and errors in the graduated staff.
- Personal errors: Errors can also be introduced by the surveyor, such as misreading the staff or misjudging the position of the crosshair in the telescope.
In conclusion, the correct statement is that the effect of curvature is to cause the objects sighted to appear lower than they really are in levelling. This is an important source of error that needs to be considered and corrected for in levelling measurements.
Explanation:
In levelling, the curvature of the Earth is one of the sources of error that needs to be considered. The effect of curvature is to cause the objects sighted to appear lower than they really are. This is because when we sight an object, we are effectively looking along a tangent line to the Earth's surface, and as we move away from the object, the line of sight becomes more and more parallel to the tangent line. This means that the line of sight does not follow the curve of the Earth, causing the object to appear lower.
Effects of Curvature in Levelling:
The effect of curvature can be significant in levelling, especially when measuring over long distances. This is because the curvature of the Earth causes the line of sight to deviate from the horizontal plane. As a result, the measured elevation of a point will be lower than the true elevation.
Compensating for Curvature:
To compensate for the curvature of the Earth, corrections need to be applied to the measured elevations. One common method is to use a correction factor called the curvature correction. The curvature correction is calculated based on the distance between the instrument and the target point. By subtracting the curvature correction from the measured elevation, the true elevation can be determined.
Other Sources of Error in Levelling:
While the effect of curvature is one source of error in levelling, there are other sources of error that also need to be considered. These include:
- Atmospheric refraction: The bending of light rays as they pass through the Earth's atmosphere can cause errors in levelling measurements. In reciprocal levelling, the error due to refraction is eliminated by taking a foresight and a backsight from each instrument station.
- Instrument errors: Levelling instruments can have inherent errors that need to be taken into account. These errors can include misalignment of the telescope, imperfect leveling of the instrument, and errors in the graduated staff.
- Personal errors: Errors can also be introduced by the surveyor, such as misreading the staff or misjudging the position of the crosshair in the telescope.
In conclusion, the correct statement is that the effect of curvature is to cause the objects sighted to appear lower than they really are in levelling. This is an important source of error that needs to be considered and corrected for in levelling measurements.
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Which one of the following statement is CORRECT?a)In levelling, if backsight is less than foresight, the back sight stations lower than the foresight station.b)In reciprocal levelling, the error due to refraction is not eliminated.c)At a change point in levelling, two backsight are taken.d)The effect of curvature is to cause the objects sighted to appear lower than they really are.Correct answer is option 'D'. Can you explain this answer?
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Which one of the following statement is CORRECT?a)In levelling, if backsight is less than foresight, the back sight stations lower than the foresight station.b)In reciprocal levelling, the error due to refraction is not eliminated.c)At a change point in levelling, two backsight are taken.d)The effect of curvature is to cause the objects sighted to appear lower than they really are.Correct answer is option 'D'. Can you explain this answer? for Civil Engineering (CE) 2024 is part of Civil Engineering (CE) preparation. The Question and answers have been prepared according to the Civil Engineering (CE) exam syllabus. Information about Which one of the following statement is CORRECT?a)In levelling, if backsight is less than foresight, the back sight stations lower than the foresight station.b)In reciprocal levelling, the error due to refraction is not eliminated.c)At a change point in levelling, two backsight are taken.d)The effect of curvature is to cause the objects sighted to appear lower than they really are.Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Civil Engineering (CE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Which one of the following statement is CORRECT?a)In levelling, if backsight is less than foresight, the back sight stations lower than the foresight station.b)In reciprocal levelling, the error due to refraction is not eliminated.c)At a change point in levelling, two backsight are taken.d)The effect of curvature is to cause the objects sighted to appear lower than they really are.Correct answer is option 'D'. Can you explain this answer?.
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