Inundation Mapping Tidal Surface - Mean Higher High Water

These data are a derived product of the NOAA VDatum tool and they extend the tool's Mean Higher High Water (MHHW) tidal datum conversion inland beyond its original extent.

VDatum was designed to vertically transform geospatial data among a variety of tidal, orthometric and ellipsoidal vertical datums - allowing users to convert their data from different horizontal/vertical references into a common system and enabling the fusion of diverse geospatial data in desired reference levels (http://vdatum.noaa.gov/). However, VDatum's conversion extent does not completely cover tidally-influenced areas along the coast. For more information on why VDatum does not provide tidal datums inland, see http://vdatum.noaa.gov/docs/faqs.html.

Because of the extent limitation and since most inundation mapping activities use a tidal datum as the reference zero (i.e., 1 meter of sea level rise on top of Mean Higher High Water), the NOAA Office for Coastal Management created this dataset for the purpose of extending the MHHW tidal datum beyond the areas covered by VDatum. The data do not replace VDatum, nor do they supersede the valid datum transformations VDatum provides. However, the data are based on VDatum's underlying transformation data and do provide an approximation of MHHW where VDatum does not provide one. In addition, the data are in a GIS-friendly format and represent MHHW in NAVD88, which is the vertical datum by which most topographic data are referenced.

Data are in the UTM NAD83 projection. Horizontal resolution varies by VDatum region, but is either 50m or 100m. Data are vertically referenced to NAVD88 meters.

These data were created to support the mapping of tidally-based inundation scenarios on high resolution digital elevation models. The data represent the MHHW tidal datum referenced to NAVD88, which is the official civilian orthometric datum by which most topographic data are referenced.

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These data do not replace valid VDatum transformations. They do not incorporate VDatum's bounding polygons (or valid transformation areas) - the data extend beyond these areas.

Any conclusions drawn from the analysis of this information are not the responsibility of the Office for Coastal Management or its partners.

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The dataset is provided as is, without warranty to its performance, merchantable state, or fitness for any particular purpose. The entire risk associated with the results and performance of this dataset is assumed by the user. This dataset should be used strictly as a planning reference and not for navigation, permitting, or other legal purposes.

Data are complete and cover all areas defined by the source data.

Standard mapping methods were used to develop the data, which are described in the Process Steps section. Outputs were inspected for errors and inconsistencies, which were addressed and remedied.