Backscatter A [CSUMB]--Offshore Coal Oil Point, California

This part of SIM 3302 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3302) of the Offshore of Coal Oil Point map area, California. The raster data file is included in "BackscatterA_CSUMB_OffshoreCoalOilPoint.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshoreCoalOilPoint/data_catalog_OffshoreCoalOilPoint.html.
The acoustic-backscatter map of Offshore Coal Oil Point, California was generated from backscatter data collected by California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB), by the U.S. Geological Survey (USGS) and by Fugro Pelagos. These metadata describe the acoustic-backscatter data collected by CSUMB and reprocessed by the USGS. See "BackscatterB_USGS_OffshoreCoalOilPt_metadata.txt" metadata for a description of the acoustic-backscatter data collected by the USGS. The far eastern nearshore and shelf region of the Offshore Coal Oil Point map was mapped by CSUMB in the summer of 2007 using a 244 kHz Reson 8101 multibeam echosounder. Within the final imagery, brighter tones indicate higher backscatter intensity, and darker tones indicate lower backscatter intensity. The intensity represents a complex interaction between the acoustic pulse and the seafloor, as well as characteristics within the shallow subsurface, providing a general indication of seafloor texture and sediment type. Backscatter intensity depends on the acoustic source level; the frequency used to image the seafloor; the grazing angle; the composition and character of the seafloor, including grain size, water content, bulk density, and seafloor roughness; and some biological cover. Harder and rougher bottom types such as rocky outcrops or coarse sediment typically return stronger intensities (high backscatter, lighter tones), whereas softer bottom types such as fine sediment return weaker intensities (low backscatter, darker tones).