Civil Engineering - Surveying - Discussion
Discussion Forum : Surveying - Section 1 (Q.No. 34)
34.
Pick up the correct statement from the following :
Discussion:
3 comments Page 1 of 1.
Jack said:
6 years ago
Please explain this in detail.
Vicky said:
4 years ago
Please explain it.
Sandesh Neupane said:
4 weeks ago
The apparent error on reversal is twice the actual error.
When an instrument is reversed (e.g. rotated 180°), any error due to misalignment or eccentricity appears doubled. This is because the error shifts direction, making the discrepancy between readings twice the actual error.
The correction may be made equal to half the observed discrepancy.
Since the apparent error is twice the actual error, the correction needed to compensate is half of what is observed. This principle is used in methods like reciprocal levelling and collimation error correction.
Good results may be obtained from a defective instrument by reversing and taking the mean of two erroneous results.
Reversing the instrument and averaging the readings helps cancel out systematic errors. This technique is commonly used in theodolite observations and levelling to improve accuracy despite imperfections.
So yes, all the above statements are correct and reflect standard practices in error mitigation during surveying.
When an instrument is reversed (e.g. rotated 180°), any error due to misalignment or eccentricity appears doubled. This is because the error shifts direction, making the discrepancy between readings twice the actual error.
The correction may be made equal to half the observed discrepancy.
Since the apparent error is twice the actual error, the correction needed to compensate is half of what is observed. This principle is used in methods like reciprocal levelling and collimation error correction.
Good results may be obtained from a defective instrument by reversing and taking the mean of two erroneous results.
Reversing the instrument and averaging the readings helps cancel out systematic errors. This technique is commonly used in theodolite observations and levelling to improve accuracy despite imperfections.
So yes, all the above statements are correct and reflect standard practices in error mitigation during surveying.
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