ANS:D - all the above.

Taken on an inverted staff is treated as negative.

Its known elevation is above. As like a shade with 2.10m in height. Then inverted staff is used to measure downwards from shade to the below point. So the reading is negative & the Value is subtracted. Q1 RL 30.5 (factory floor)staff reading of floor 1.61 staff reading when staff is inverts with bottom touching tie beam of truss is 3.7 m find height of tie beam above floor,