Seafloor character--Drakes Bay and Vicinity, California

The seafloor-character map was produced using video-supervised maximum likelihood classification of the bathymetry and intensity of return from sonar systems. The classification was supervised using signatures defined by hand-drawn polygons located through sediment samples and video-observation ground truth data by applying methodology described in Cochrane (2008). The two variants used in this classification were backscatter intensity and derivative rugosity. Rugosity measures terrain ruggedness as the variation in three-dimensional orientation of grid cells within a neighborhood. Vector analysis is used to calculate the dispersion of vectors normal (orthogonal) to grid cells within the specified neighborhood. This method effectively captures variability in slope and aspect into a single measure. Ruggedness values in the output raster map can range from 0 (no terrain variation) to 1 (complete terrain variation). The calculation was performed using the Terrain Ruggedness (VRM) tool (for details, see Sappington and others, 2007). Classes I, II and III values were delineated using multivariate analysis. Class IV (mobile sedimentary features) values were determined on the basis of visual characteristics using both bathymetry and backscatter (slight depression in the seafloor, very high backscatter return). The resulting map (gridded at 2 m) was cleaned by hand to remove data-collection artifacts (for example trackline nadir). Editing was performed in Photoshop, where individual pixels were selected and values adjusted to remove noise. Selection occurred without antialiasing, and the resulting grid was identical but for the edited pixels. The four seafloor classes were then colored to indicate which of the five California MLPA depth zones they are located in: Depth Zone 2 (intertidal to 30 m), Depth Zone 3 (30 to 100 m), Depth Zone 4 (100 to 200 m), or Depth Zone 5 (greater than 200 m). These were further subdivided into one of the following slope classes: Slope Class 1 (0 degrees - 5 degrees), Slope Class 2 (5 degrees - 30 degrees), Slope Class 3 (30 degrees - 60 degrees), or Slope Class 4 (60 degrees - 90 degrees). Depth Zone 1 (intertidal), Depth Zone 4-5 (greater than 100 m), and Slope Classes 3-4 (greater than 30 degrees) are not present in the Drakes Bay and Viciniy region.

Added Distribution_Information section to metadata to facilitate data download.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata.

Metadata was modified to bring up to current USGS PCMSC standards. USGS Thesaurus and keywords were added, and Process Steps were refined. Minor typos were corrected. No data information was changed.

Information for accompanying Open-File Report added to Abstract and Cross Reference sections. Point of Contact information was updated. Details about different Network Resource Name links was given in the Access Instructions section. Phone number for Metadata Contact was corrected. No data information was changed.

Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed.

Edited metadata to correct onlink tag information. No data were changed. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata date of this file to any similar file to ensure they are using the most recent version.