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Historical Bathymetry in the Mississippi-Alabama Coastal Region: Bathymetric Soundings, Gridded Digital Elevation Model, and Hydrographic Sheets (Ver. 2.0)

March 24, 2022

Hydrographic sheets (H-sheets) produced by the National Ocean Service (NOS) during the 1800s provide historic sounding (water depth) measurements of coastal areas. The data can be vectorized into a geographic information system (GIS), adjusted to a modern vertical datum, and converted into a digital elevation model to provide an interpretation of the historic seafloor elevation. These data were produced to provide an estimate of historical bathymetry for the Mississippi-Alabama coastal region to aid geologic and coastal hazards studies. This data release includes georeferenced H-sheets, depth soundings, and a bathymetric grid from 1852 and 1853. The original NOS H-sheets were scanned by the National Oceanic and Atmospheric Administration (NOAA) and are available through the National Geophysical Data Center (NGDC) website ( as non-georeferenced digital raster files. U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC) staff performed the following procedures: H-sheets were georeferenced, georeferenced raster images were projected to a modern datum, and digitized historical bathymetric sounding measurements were used to create a vector point shapefile. Sounding data was converted from feet to meters, converted to modern mean sea level, and finally converted to the North American Vertical Datum of 1988 (NAVD88) GEOID12A using VDatum. Please read the full metadata for details on data collection, dataset variables, and data quality.