BackscatterB [EM300]--Monterey Canyon and Vicinity, California

This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate grids depending on mapping system and processing method. These metadata describe acoustic-backscatter data collected and processed by the U.S. Geological Survey. The raster data files are included in "BackscatterB_EM300_MontereyCanyon.zip," which is accessible from http://dx.doi.org/10.5066/F7XD0ZQ4.
The acoustic-backscatter map of Monterey Canyon and Vicinity, California, were generated from acoustic-backscatter data collected by the U.S. Geological Survey (USGS), by Monterey Bay Aquarium Research Institute (MBARI), and by California State University, Monterey Bay (CSUMB). Mapping for the entire map area was completed between 1998 and 2014 using a combination of 30-kHz Simrad EM-300 and 200-kHz/400-kHz Reson 7125 multibeam echosounders, as well as 234-kHz and 468-kHz SEA SWATHplus bathymetric sidescan-sonar systems. The MBARI mapping was completed in 1998, the data were downloaded and reprocessed by the USGS in 2014. 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蒙特利峡谷及周边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与处理方法的不同，以独立栅格形式提供。这些元数据描述了由美国地质调查局（U.S. Geological Survey, USGS）采集并处理的声学反向散射数据。栅格数据文件包含在"BackscatterB_EM300_MontereyCanyon.zip"中，可通过http://dx.doi.org/10.5066/F7XD0ZQ4获取。

加利福尼亚州蒙特利峡谷及周边区域的声学反向散射地图，由美国地质调查局（USGS）、蒙特利湾水族馆研究所（Monterey Bay Aquarium Research Institute, MBARI）以及加州州立大学蒙特利湾分校（California State University, Monterey Bay, CSUMB）采集的声学反向散射数据生成。整个测绘区域的测绘工作于1998年至2014年间完成，使用了30-kHz Simrad EM-300多波束回声测深仪、200-kHz/400-kHz Reson 7125多波束回声测深仪，以及234-kHz和468-kHz SEA SWATHplus水深侧扫声呐系统。MBARI的测绘工作于1998年完成，美国地质调查局于2014年对该数据进行了下载与重新处理。在最终生成的影像中，色调越亮代表反向散射强度越高，色调越暗代表反向散射强度越低。该强度值反映了声脉冲与海底及浅地下层特征之间的复杂相互作用，可大致指示海底纹理与组成成分。反向散射强度取决于声学源级、海底成像所用频率、掠射角、海底的组成与特性（包括粒度、含水量、体积密度及海底粗糙度），以及部分生物覆盖物。坚硬且粗糙的底质（如岩石露头或粗颗粒沉积物）通常会返回更强的信号（高反向散射，色调较亮），而柔软的底质（如细颗粒沉积物）则会返回较弱的信号（低反向散射，色调较暗）。