Backscatter C [7125]--Drakes Bay and Vicinity, California

This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity 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_7125_DrakesBay.zip", which is accessible from http://pubs.usgs.gov/ds/781/DrakesBay/data_catalog_DrakesBay.html.

The acoustic-backscatter map of Drakes Bay and Vicinity map area, California, was generated from backscatter 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 Californiaís 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.

本数据集隶属于DS 781系列，包含加利福尼亚州德雷克湾及周边制图区的声背散射（acoustic-backscatter）地图数据。根据测绘系统与处理方法的不同，背散射数据以独立网格形式提供。所需栅格数据文件收录于"BackscatterC_7125_DrakesBay.zip"压缩包中，可通过以下链接获取：http://pubs.usgs.gov/ds/781/DrakesBay/data_catalog_DrakesBay.html。

加利福尼亚州德雷克湾及周边制图区的声背散射地图，其数据由蒙特雷湾加利福尼亚州立大学（California State University, Monterey Bay, CSUMB）与Fugro Pelagos公司采集。测绘工作于2007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。本次联合测绘任务采集的背散射数据覆盖范围约为10米等深线至加利福尼亚州领海3海里边界以外区域。

在声背散射影像中，色调越亮代表背散射强度越高，色调越暗则代表背散射强度越低。背散射强度反映了声脉冲与海底、浅地表内部特征之间的复杂相互作用，可用于大致指示海底纹理与物质组成。背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、海底组成与特征（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。质地坚硬且粗糙的海底类型（如岩层出露区或粗颗粒沉积物）通常会产生更强的背散射信号（高背散射强度，对应亮色调）；而质地松软的海底类型（如细颗粒沉积物）则会产生较弱的背散射信号（低背散射强度，对应暗色调）。本数据集不可用于导航用途。