Backscatter C [Swath]--Offshore of Fort Ross, California

This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Fort Ross map area, California. Backscatter data are provided as separate grids depending on mapping system or processing method. The raster data file is included in "BackscatterC_Swath_OffshoreFortRoss.zip", which is accessible from http://pubs.usgs.gov/ds/781/OffshoreFortRoss/data_catalog_OffshoreFortRoss.html. The acoustic-backscatter map of the Offshore of Fort Ross map area, California, was generated from backscatter data collected by California State University, Monterey Bay (CSUMB) and by Fugro Pelagos. Mapping was completed between 2007 and 2010, using a combination of 200-kHz and 400-kHz Reson 7125, and 244-kHz Reson 8101 multibeam echosounders, as well as 468-kHz SEA SWATHPlus interferometric system. These mapping missions combined to collect backscatter data from about the 10-m isobath to beyond the 3-nautical-mile limit of California State Waters. Within the acoustic-backscatter 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). These data are not intended for navigational purposes.本数据集DS 781的此部分提供了加利福尼亚州罗斯堡近海测绘区的声学反向散射（acoustic-backscatter）地图数据。反向散射数据会根据测绘系统或处理方法的不同，以独立网格的形式提供。栅格数据文件包含于"BackscatterC_Swath_OffshoreFortRoss.zip"压缩包中，可通过http://pubs.usgs.gov/ds/781/OffshoreFortRoss/data_catalog_OffshoreFortRoss.html获取。 加利福尼亚州罗斯堡近海测绘区的声学反向散射地图，其数据由加州州立大学蒙特雷湾分校（CSUMB）与Fugro Pelagos公司采集所得。本次测绘工作于2007年至2010年间完成，所用设备包括200kHz与400kHz的Reson 7125、244kHz的Reson 8101多波束测深仪，以及468kHz的SEA SWATHPlus干涉测量系统。本次测绘任务共采集了从约10米等深线至加州州属海域3海里边界以外区域的反向散射数据。在声学反向散射影像中，亮色调代表更高的反向散射强度，暗色调则代表更低的反向散射强度。反向散射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，可大致反映海底的质地与组成。反向散射强度受多种因素影响：声源级、海底成像所用频率、掠射角、海底的组成与特征（包括粒径、含水量、体积密度及海底粗糙度），以及部分生物覆盖层。质地坚硬且粗糙的海底类型（如岩石露头或粗粒沉积物）通常会产生更强的反向散射信号（高反向散射，对应亮色调），而质地柔软的海底类型（如细粒沉积物）则会产生较弱的反向散射信号（低反向散射，对应暗色调）。本数据集并非用于导航用途。