Contributed by the NHC Storm Surge Unit

A vertical datum is an established surface that serves as a reference to measure of model heights and depths. All water level observations, including SLOSH storm surge heights, are referenced as height above a vertical datum. Currently, the SLOSH model utilizes the National Geodetic Vertical Datum of 1929 (NGVD29) and the North American Vertical Datum of 1988 (NAVD88). All basins are being updated to NAVD88 because NGVD29 is out-dated and no longer being supported.

It is important to note that when comparing water level observations (e.g. tide stations) with other observations, observations with models, or models to other models, on MUST always use consistent vertical datums.

Last updated May 14, 2010

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