5-meter bathymetric data collected in 2014 by the U.S. Geological Survey along the Delmarva Peninsula, MD and VA (32-bit GeoTIFF, UTM Zone 18N, WGS 84)

Each raw BathySwath bathymetric sonar file (sxr) was converted to a processed file (sxp) using BathySwath Processor (vers. 3.10.0.2; this new version allows the import of nearly an unlimited number of sound velocity profiles. This makes the process of recreating sxp files much easier if the data need reprocessing - which they did for this survey). During the conversion process, sound velocity profiles were used to minimize potential refraction artifacts from fluctuations in the speed of sound within the water column. Several bathymetric filters were applied to remove erroneous soundings and reduce the density of the data. Observed tidal corrections were applied later in the processing flow after observed tides were released from NOAA's Tides and Currents website, which is typically a 2-4 week lag. Bathymetric filtering typically included low amplitude (100%), range (0-4m), box (3-50m depth, 1.5-75m horizontal), median (window size 5), alongtrack 1 (depth difference of 5-m, window size 5-m, and learn rate of 0.7), alongtrack 2 (depth difference of 1.5-m, window size 1m, and learn rate of 0.9), and mean filters (0.25m). These represent the typical parameters used for the majority of the USGS surveys although the values may have been adjusted slightly for specific parts of the survey area.

A new CARIS HIPS project (vers. 9.0.6) was created with projection information set to Universal Transverse Mercator (UTM) Zone 18, WGS84. Each BathySwath reprocessed file (sxp) was imported to the new CARIS project using the Import/Conversion Wizard. A 5 meter resolution Bathymetric and Statistical Error (BASE) Surface was created from the files for each Julian day. The BASE surface for each day was reviewed for any inconsistencies or data anomalies. Navigation was reviewed and edited as needed using the navigation editor tool. Beam-to-beam slopes and across track angle filters were applied to the soundings line by line. The refraction editor was used to adjust sound speed values in areas where velocimeter data did not adequately correct depth profiles obviously influenced by local anomalies in speed of sound through the water column.

Within CARIS (version 9.0.6) tide corrections (to MLLW) were applied using a discrete tidal-zoning model (DTZ) developed by NOAA/NOS's Hydrographic Planning Team (Huang, personal communication, 2010) (<http://www.tidesandcurrents.noaa.gov/hydro.html>). The DTZ model corrects differences in tidal phase and amplitude between the survey area and observations made at NOS tide gauges at Atlantic City, NJ(8534720), Lewes, DE (8557380), Chesapeake Bay-Bridge-Tunnel, VA (8638863) and Duck NC (8651370). The tidal zone model was imported into CARIS (version: HIPS and SIPS 9.0.6) as a zone definition file (ZDF) and the tide gauge data were loaded as caris .tid format files. Following tide correction, each line was re-merged and a BASE surface for the entire survey areas was computed to incorporate the MLLW verified tide information. Additional swath editing was done in CARIS using the swath and area based editors to remove additional inconsistencies and minimize survey artifacts. The CARIS HIPS BASE surface was exported from CARIS as a Bathymetry Attributed Grid (BAG) file and then imported into ArcMap version 10.2. This creates an Esri Grid format file with 3 separate file folders. To avoid this cumbersome translation from BAG to Esri format, the data were converted to a 32-bit GeoTIFF using DEFLATE compression for transfer purposes. Also within ArcMap a .tfw file was created using the export raster world file tool. Although the processing steps described here are very similar to the processing steps described in version 1 of this dataset. This grid represents a more finalized version including refraction editing, swath editing, and stricter depth filtering. This version should be used instead of version 1.

The online links to the data were updated to reflect the new server hosting the data. Additionally, other small edits could be made to the metadata, such as modifying http to https where appropriate. The metadata date (but not the metadata creator) was edited to reflect the date of these changes.

Added keywords section with USGS persistent identifier as theme keyword.