Hydrographic surveys are referenced vertically to a local water level “chart” datum. Conducting a survey relative to the ellipsoid dictates a datum transformation take place before the survey is used for current navigational products. Models that combine estimates for the tide, sea surface topography, the geoid, and the ellipsoid are often used to transform an ellipsoid referenced survey to a local water level datum. Regions covered by these vertical datum transformation models are limited and so would appear to constrain the areas where ellipsoid referenced surveys can be conducted. Because areas not covered by a vertical datum transformation model still must have a tide model to conduct a hydrographic survey, survey‐ time measurements of the ellipsoid to water level datum can be conducted through the vessel reference point. This measured separation is largely a function of the vessel ellipsoid height and the standard survey tide model and thus introduces limited additional uncertainty than is typical in a water level referenced survey. This approach is useful for reducing ellipsoid reference surveys to the water level datum, examining a tide model, or for evaluating a vertical datum transformation model. Prototype tools and a comparison to typical vertical datum transformation models are discussed.


Center for Coastal and Ocean Mapping

Publication Date


Journal or Conference Title

U.S. Hydrographic Conference

Conference Date

April 25-28, 2011

Publisher Place

Tampa, FL, USA


Hydrographic Society of America

Document Type

Conference Proceeding