BackscatterC [SWATH]--Offshore Pigeon Point, California

This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate grids depending on mapping system. The raster data files are included in "BackscatterC_SWATH_OffshorePigeonPoint.zip," which is accessible from http://dx.doi.org/10.5066/F7513W80.
The acoustic-backscatter map of the Offshore of Pigeon Point, California was generated from backscatter data collected by California State University, Monterey Bay (CSUMB), by Fugro Pelagos, and by the U.S. Geological Survey (USGS). Mapping was completed between 2006 and 2009, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 234-kHz SWATHplus bathymetric sidescan-sonar system. 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 composition. 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).

DS 781的本部分提供了加利福尼亚州鸽子角近海制图区域的声学反向散射（acoustic-backscatter）地图数据。反向散射数据根据测绘系统分为三个独立网格。栅格数据文件存储于"BackscatterC_SWATH_OffshorePigeonPoint.zip"压缩包中，可通过链接http://dx.doi.org/10.5066/F7513W80获取。
加利福尼亚州鸽子角近海的声学反向散射地图，由加州州立大学蒙特利湾分校（California State University, Monterey Bay, CSUMB）、Fugro Pelagos公司以及美国地质调查局（U.S. Geological Survey, USGS）采集的反向散射数据生成。测绘工作于2006年至2009年间完成，所用设备包括400kHz Reson 7125与244kHz Reson 8101多波束测深仪（multibeam echosounders），以及234kHz SWATHplus水深侧扫声呐系统（bathymetric sidescan-sonar system）。在最终生成的影像中，较亮色调代表更高的反向散射强度，较暗色调则代表更低的反向散射强度。该强度反映了声脉冲与海底以及浅地下层特征之间的复杂相互作用，可用于大致指示海底纹理与组成成分。反向散射强度受多项因素影响：声源级、海底成像所用声波频率、掠射角、海底的组成与特征（包括粒度、含水量、堆积密度及海底粗糙度），以及部分海底生物覆盖物。质地坚硬且粗糙的海底类型（如岩石露头或粗粒沉积物）通常会返回更强的信号强度（高反向散射，对应较亮色调），而松软的海底类型（如细粒沉积物）则会返回较弱的信号强度（低反向散射，对应较暗色调）。