Mining Geology, Mine Development and Surveying · Mine Surveying · 2 marks · Numerical answer
A dumpy-level bubble has sensitivity 40″ per division. At a staff distance 60 m, the bubble is two divisions off centre. Find staff-reading error magnitude in mm, to one decimal.
Angular error is 80 arcseconds, or 80π/(180×3600) radians. Height error is 60000×tan(angle)≈23.2711 mm. Report 23.3 mm. Arcseconds must be converted to radians before using the small-angle approximation.
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