Converter
vertical reference · Hydrography/geodesy · Modern/historical
chart datum
reference-only
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- M673
- Definition quality
- Standardized
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Definition
Chart datum is the vertical reference surface from which charted depths and tidal heights are measured.
History & use
NOAA hydrographic data are adjusted to a standard water-level datum before final chart soundings are produced.
Modern use
Modern use is context-dependent and varies by region or measurement system.
Sources & evidence
Source tier — · confidence high
- Hydrographic Surveys Division, Office of Coast Survey, NOAA — https://www.nauticalcharts.noaa.gov/publications/documents/HSSD_2026-0-02.pdf
- Center for Operational Oceanographic Products and Services, NOAA National Ocean Service — https://tidesandcurrents.noaa.gov/publications/tidal_datums_and_their_applications.pdf