A level instrument at a height of 1.320 m has been placed at a station having a Reduced Level (RL) of 112.565 m. The instrument reads -2.835 m on a levelling staff held at the bottom of a bridge deck. The RL (in m) of the bottom of the bridge deck is

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Accepted Answer

116.720. Height of collimation = 112.565 + 1.320 = 113.885 m. The bridge soffit is above the line of sight, giving the inverted (negative) staff reading, so RL = 113.885 - (-2.835) = 116.720 m, which is option index 0, not the stored 116.080.

A level instrument at a height of 1.320 m has been placed at a station having a Reduced Level (RL) of 112.565 m. The instrument reads -2.835 m on a levelling staff held at the bottom of a bridge deck. The RL (in m) of the bottom of the bridge deck is

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