Answer
Ans. Crankshaft deflection before and after DD is taken by chief engineer himself.
Before DD the deflection is taken to mark it as reference.
In Dry doc
The vessel sits on the keel blocks and there can be distortion of the bed plate which can lead to deformation of the bearing seats which can further lead to damage to the bearing.
Any repairs or renewal of bearings carried out during DD so we can cross check all fittings are done as per order.
Any jobs carried out on main engine holding down bolts, chokes.
So the readings which are taken after DD will guide us if any urgent attention is required before any major damage happens.