Hydrographic Chart
F5. The Reference Layer: Glossary, Units, Signals and Information SourcesDefinition
Nautical chart produced by a hydrographic office.
A nautical (hydrographic) chart is the surveyed representation of the seabed and coast for navigation: charted depths reduced to a chart datum, drying heights, the nature of the bottom, lights, marks, hazards, and traffic schemes. Depths are referenced to a low-water datum (Lowest Astronomical Tide on Admiralty charts) so charted depth is the safe minimum; heights of lights and bridges use a high-water datum. Paper charts are produced by national hydrographic offices; ENCs are the vector equivalent for ECDIS.