Method and apparatus for active heave compensation

An apparatus for controlling active heave compensation, the arrangement being such that, in use, said apparatus controls movement of a connection device that connects a load to a vessel, which apparatus comprises an input for receiving a heave signal from a measurement device, which heave signal is representative of the heave of said vessel, which heave signal comprises a velocity signal representing velocity of said vessel in response to said heave;

• which apparatus further comprises a memory storing computer executable instructions for performing the steps of:
• (a) using said heave signal to compensate for said heave by moving said connection device relative to said vessel as a function of said heave signal, whereby movement of said load due to said heave is reduced;
• said heave signal comprising errors induced by said measurement device whereby accuracy of said compensation is reduced;
• (b) processing said heave signal by determining a velocity correction (vG) and adjusting said velocity signal by said velocity correction so as to reduce said errors and outputting an adjusted heave signal;
• and
• (c) using said adjusted heave signal to move said connection device to compensate for said heave.