The Port of Holyhead contracts hydrographic survey services, enabling the charting of the harbour area.  Surveys are conducted to the standard required by the International Hydrographic Office (IHO) SP44.  Dredging takes place at scheduled intervals and is closely monitored and managed by the Harbour Master’s department.  In accordance with the Code, hydrographic records are maintained and passed to the UK Hydrographic Office (UKHO) to update their records.