BackscatterC [7125]--Offshore of Salt Point Map Area, California

This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Salt Point map area, California. Backscatter data are provided as separate grids depending on mapping system or processing method. The raster data files are included in "Backscatter7125_SaltPoint.zip", which are accessible from http://pubs.usgs.gov/ds/781/OffshoreSaltPoint/data_catalog_OffshoreSaltPoint.html.

The acoustic-backscatter map of the Offshore of Salt Point 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.

本数据集属于DS 781系列的一部分，展示了加利福尼亚州索尔特角近海制图区域的声学反向散射（acoustic-backscatter）地图数据。反向散射数据根据所采用的制图系统或处理方法，被划分为多个独立网格。所有栅格数据文件均包含于"Backscatter7125_SaltPoint.zip"压缩包中，可通过链接 http://pubs.usgs.gov/ds/781/OffshoreSaltPoint/data_catalog_OffshoreSaltPoint.html 获取。

加利福尼亚州索尔特角近海制图区域的声学反向散射地图，由加州州立大学蒙特雷湾分校（California State University, Monterey Bay, CSUMB）与Fugro Pelagos采集的反向散射数据生成。该制图工作于2007年至2010年间完成，使用了200kHz与400kHz的Reson 7125、244kHz的Reson 8101多波束回声测深仪（multibeam echosounders），以及468kHz的SEA SWATHPlus干涉测量系统（interferometric system）。本次联合制图任务共采集了约10米等深线至加州州管辖海域3海里以外区域的反向散射数据。在声学反向散射影像中，较亮的色调对应更高的反向散射强度，较暗的色调则对应更低的反向散射强度。反向散射强度是声脉冲与海底及浅表层地下特征之间复杂相互作用的结果，可用于大致反映海底的纹理与组成特征。反向散射强度受多种因素影响：声源级、海底成像所用声波频率、掠射角、海底的组成与性质（包括粒度、含水率、体积密度及海底粗糙度），以及海底生物覆盖情况。质地坚硬且粗糙度较高的底质类型（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），而松软底质（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）。本数据集并非用于导航用途。