Interpretation of the elevation of the base of the Holocene ravinement derived from seismic data collected within the new York Bight by the U.S. Geological Survey, 1995 - 1998 (Grid, UTM Zone 18N, WGS84 and Esri polyline shapefile, Geographic, WGS84)

Processed SEG-Y seismic data and associated shot navigation data acquired in 1998 within the New York Bight Apex were loaded into Landmark Seisworks interpretation software. The reflector at the base of the moderen marine sand was digitized along with the seafloor reflector. The difference in two-way travel time between horizons was calculated and converted to meters using an assumed velocity of 1630 m/s. This represents the thickness of Holocene deposits. The resolution of the CHIRP data was poor in the southeastern portion of the survey area. It was difficult to resolve Holocene deposits; the thickness of the deposit may be beyond the resolution of the system. These data were exported from seisworks to an ASCII format file.

A Holocene Isopach was generated for a portion of the inner-continental shelf within the New York Bight Apex as part of an MS Degree in 1998 (Source_Information 2). The base of the Holocene was not easily resolved within the CHIRP data, and thus, there were a limited number of 'picks' to the base of the Holocene; limited data from which to generate an isopach. The Holocene Isopach was generated by hand using a 5 meter contour interval. Recently, the USGS has revisited these data in order to refine the existing Holocene Isopach. This original Holocene Isopach was digitized and imported into ArcView. The contours of Holocene thickness were converted into an ArcInfo grid file using the ArcInfo TopoGridTool. The resultant grid was then desampled by extracting grid nodes at five minute intervals along the survey tracklines. The grid was desampled in order to limit any bias in the data introduced by converting the 5 meter isopach contours to a continuous grid; i.e. to aviod imparting a higher resolution to the data than is reasonable. These data were then exported in ASCII format file.

ASCII point data were merged and imported to Dynamic Graphics Inc., EarthVision surface modelling software. These data were gridded at a 100 meter grid cell size, yielding 1061 rows and 1853 columns grid size. Bathymetric data that were collected the same time as the seismic profile data were gridded using a 150 m grid cell size. The Holocene isopach grid was addded to the bathymetric grid to yield a grid for the elevation of the Holocene Ravinement reference to mean low water. This grid was exported as an ASCII format file.

The exported ASCII grid file from EarthVision was edited to create an ASCII grid file suitable for import to ArcView software. The order of rows were flipped, so that the file begins with the lower row, left column and ends with the upper row right column. An ArcView header that descibes the lower left origin of the grid, the grid cell size, the number of rows and columns, and the null value used (-9999).

The edited ASCII grid file was imported into ArcView software with the 3D Spatial Analyst extension. The file was saved as an ESRI raster grid.

Contour data were generated from the Holocene Ravinement Gridded data at a 5 meter contour interval within EarthVision. These data were exported and converted to an ESRI generate format. The contour interval associated with each contour was saved as an ASCII file and read into ArcView in table format. The generate file was converted to a vector shapefile. The table and attritube table of the contour shapefile were joined based on unique contour IDs. The attribute table was then editted to include the associated contour value with each contour line, and the join was removed. These contour data are stored in the Geographic Coordinate System (decimal degrees, WGS84 Ellipsoid).

The grid and contour data were clipped, using the GRIDCLIP script within ArcView 3.2, to the extents of the 1995 and 1996 surveys.

Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Completely changed the title based on an author (Jane Denny) supplied title. Added online links to the publication and data page in the Identification section. Added the standard order section to the Distribution Information, which included providing a link to download the data. The metadata describes both the grid and the contours, but the contours are the only dataset available for download in a zip file from the publication. Downloading the grid would require downloading individual files within folders. Fixed a source citation online link. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent.

Added keywords section with USGS persistent identifier as theme keyword.