Charleston Harbor, SC (S080) Bathymetric Digital ElevationModel (30 meter resolution) Derived From Source Hydrographic SurveySoundings Collected by NOAA

Bathymetry for Charleston Harbor was derived from seventeen surveysconsisting of 87,874 soundings. Six entire older, overlapping, lessaccurate surveys were omitted. The overlap from five older, lessaccurate surveys was omitted before tinning. The averageseparation between soundings was 31 meters. Five of the surveysused dated from 1934 and were located in the south. The remainingtwelve surveys dated from 1947 to 1978. The total rangeof sounding data was 1.5 meters to -25.3 meters at mean low water.Mean high water values between 1.0 and 1.7 meters were assignedto the shoreline. Four points were found that were notconsistent with the surrounding data. These were removed priorto tinning. DEM grid values outside the shoreline (on land) wereassigned null values (-32676).Charleston Harbor has nine 7.5 minute DEMs and three one degree DEMs.The 1 degree DEMs were generated from the higher resolution 7.5minute DEMs which covered the estuary. A Digital Elevation Model(DEM) contains a series of elevations ordered from south to northwith the order of the columns from west to east. The DEM isformatted as one ASCII header record (A- record), followed by aseries of profile records (B- records) each of which include a shortB-record header followed by a series of ASCII integer elevations(typically in units of 1 centimeter) per each profile. The lastphysical record of the DEM is an accuracy record (C-record).The 7.5-minute DEM (30- by 30-m data spacing) is cast on theUniversal Transverse Mercator (UTM) projection. It provides coveragein 7.5- by 7.5-minute blocks. Each product provides the samecoverage as a standard USGS 7.5-minute quadrangle but the DEMcontains over edge data. Coverage is available for many estuaries ofthe contiguous United States but is not complete.