Bilingual (Chinese and English) paper nautical charts are produced in accordance with the specifications of the International Hydrographic Organization (IHO). The positions on the chart are referred to the WGS84 Datum. The depths are in metres and reduced to the Chart Datum, which is approximately the Lowest Astronomical Tide. The buoyage system in Hong Kong follows the IALA Maritime Buoyage System (Region A), i.e. Red to Port, Green to Starboard.