An assembly, system and method for compensating a crane position offset error based on wheel float by viewing, with an optical sensor located on a trolley on the crane, a target or target shape adjacent a storage rack containing a vertically stored mill roll and determining a positional compensation signal based on a separation or offset of a center of a field of view of the sensor from a center of the target shape. The assembly, system or method compensates for the crane position offset error by moving the crane, as instructed by the positional compensation signal, a distance equal to the separation or offset of the center of the field of view of the sensor from the center of the target.