What is the relationship between the geodetic vertical datums (NGVD 29 and/or NAVD 88) and the various water level/tidal datums?
NGS develops and maintains the current national geodetic vertical datum, NAVD 88. In addition, NGS provides the relationships between past and current geodetic vertical datums, e.g., NGVD 29 and NAVD 88. However, another part of our parent organization, NOS (National Ocean Service), is the Center for Operational Oceanographic Products and Services (CO-OPS). CO-OPS publishes tidal bench mark information and the relationship between NAVD 88 and various water level/tidal datums (e.g., Mean Lower Low Water, Mean High Water, Mean Tide Level, etc.). The relationships to NGVD 29 are not published, but may be calculated independently from specified tidal bench mark sheet links to the NGS data base.
