The data supplied on this CD-ROM are made available with geographic coordinates to allow the data to be incorporated into a Geographic Information System (GIS). The data layers along with additional base map layers have been compiled into an ArcViewTM project file (usSEABED_GoMex.apr), which is located at the top-level directory of this publication. The project file serves to provide an example of how the data can be displayed in a GIS. It contains several views including one which shows the Munsell color legend on the PRS data. A variety of base map layers that can be used to accompany these data can be found on the Coastal and Marine Geology Program's U.S. Gulf of Mexico Region Map Server. Several have been included below and are used in the project file. Other examples of ways to visualize these data are also included.
For those who do not have the ESRI software or a compatible GIS data browser available on their computer, a free viewer, ArcExplorer, is available from ESRI. Please note that the ArcExplorer software is limited to the Microsoft Windows operating systems.
Clicking on the layer name under the column header "Data Layer Name & Description" in the table below will open a new window with a graphical representation of that layer. Federal Geographic Data Committee (FGDC) metadata are included with data layers in three formats in the table below: (HTML, FAQ, and text).
A downloadable zip archive file containing the elements that comprise the ArcView shapefile for each data layer is also provided. Each zip file includes:
- ArcView shapefile for each layer (with associated files)
- comma-delimited text version of the data file
- all three versions of the metadata
- browse graphic of the data layer
The zip files were created using WinZip v. 8.1. Users may obtain a free copy of the software from www.winzip.com.
In addition to the ArcView shapefile, the usSEABED data layers are available in an ASCII text format as an alternate way to view and examine the data sets. The first record of the ASCII file contains the name of the data fields for that file.
GMX_SRC – A comma-delimited text file containing a list of sources included in the output files. Also included is a list of all sources of data with links to associated metadata where available. Clicking on the DataSetKey will open a new window showing a browse graphic of that particular data set. Clicking on the DataSet name will open a new window showing the HTML metadata for that particular data set. As an important note, in the processing of both the Gulf of Mexico and Caribbean data, there are a few instances of duplicate DataSetKey numbers. The title of the data set as well as the location noted will make it clear as to which set any selected data has come from.
usSEABED Gulf of Mexico and Caribbean Data
Base Map Layers
To map the coded information on Color and Roughness in a GIS, load the ArcView legends "munsell3.avl" or "rgh_pt.avl" which are available with the database. ArcView legends may be imported into ArcGIS. To make your own legends for other applications, employ a classification that uses a "unique value" process
Color of sediment is described either in terms (brown, light greenish gray) or in Munsell color codes given in values of hue (spectral content), value (lightness), and chroma (saturation). Munsell codes are explained in a publication of the Geological Society of America (Goddard and others, 1951).The dbSEABED program converts the former into average values of Munsell codes, rounded to increments of 5 in hue, 3 in value, and 3 in chroma (Jenkins, 2003). An ESRI® ArcView legend is included for ease of mapping.
This is a coded output representing the V:H of the seabed roughness element which is observed with greatest aspect ratio. That feature may be fixed roughness like a cobble, or moveable roughness like ripples. The outputs can only report observed roughness elements, so are influenced by the size scales of samplers and observations.
The V and H values are the centimeter values of the height and horizontal dimensions written in integer log 2 (base 2). For example "4:6" represents 16 cm height over length scale of 64 cm. Powers <0 are set to zero (i.e., scales <1 cm are not considered). The horizontal length H are the length of expression of a feature, rather than wavelength of repetition. Where a feature is elongated, H is taken normal to elongation (i.e., equals ripple wavelength).
Roughness: AVL | JPG