The 'reduction to mean sea level' correction in precise surveying accounts for:
Choose the correct answer
Correcting for staff graduation errors
Reducing measured length at elevation H to equivalent distance at sea level: L_MSL = L×R/(R+H)
Correcting for magnetic declination
Adjusting for tide cycles
Correct Answer
B. Reducing measured length at elevation H to equivalent distance at sea level: L_MSL = L×R/(R+H)
Why is this the answer?
MSL reduction: measured horizontal length on curved Earth at height H above MSL must be reduced to equivalent arc at MSL. Correction: L_MSL = L_meas × R/(R+H) where R ≈ 6370 km. For H=1000 m: correction = -1/6370 × L ≈ -0.157 mm/m. Significant for high-altitude surveys and geodetic surveys. In precise engineering surveys (tunnels in mountains), this correction is necessary for consistency.
Related Surveying MCQs
More solved Surveying questions for AE/JE Civil Engineering exams.
- A 'Digital Elevation Model' (DEM) is used in GIS for:
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- The 'photogrammetric control' (ground control points) in aerial survey are required for:
- The 'EDM' (Electronic Distance Measurement) instrument measures distances using:
- The 'photogrammetric stereomodel' from two overlapping aerial photos allows...
- The 'corrections' applied to measured chain/tape lengths include all EXCEPT:
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