Abstract: A storage stores at least one piece of registered correction data including a plurality of registered values associated with a plurality of section angle ranges. A controller executes parallel winch control of causing a derricking winch and a hoisting winch to operate. The controller specifies a reference target value corresponding to a derricking angle, from the plurality of registered values. In a correction period corresponding to a point of time at which a correction operation is detected, the controller corrects the reference target value used for deriving an operation speed of the hoisting winch in the parallel winch control, in accordance with a specified value specified by the correction operation. The controller updates data of the reference target value corresponding to the correction period to data corrected with the specified value.

Abstract: An information presentation system includes: an overload preventing device that derives a load factor which is an index of a load applied to a rope; a data logger that accumulates data on the load factor derived by the overload preventing device and data on a time length for which a load corresponding to the derived load factor has been applied to the rope, the data on the load factor and the data on the time length being associated with one another, and generates lifting rope statistical information and raising rope statistical information indicating a relationship between the load factor and the cumulative time for each rope; and a presenting unit that presents the lifting rope statistical information and the raising rope statistical information generated by the data logger.