Backscatter A [CSUMB]--Offshore of Carpinteria, California

This part of SIM 3261 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3261) of the Offshore of Carpinteria map area, California. The raster data file is included in "BackscatterA_CSUMB_OffshoreCarpinteria.zip," which is accessible from http://pubs.usgs.gov/ds/781/OffshoreCarpinteria/data_catalog_OffshoreCarpinteria.html. The acoustic-backscatter map of the Offshore of Carpinteria map area, California, was generated from backscatter data collected by California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB) and by the U.S. Geological Survey (USGS). These metadata describe the acoustic-backscatter data collected by CSUMB and reprocessed by the USGS. See "BackscatterB_USGS_OffshoreCarpinteria_metadata.txt" metadata for a description of the acoustic-backscatter data collected by the USGS. The southeastern nearshore and shelf areas, as well as the western midshelf area, were mapped by CSUMB in the summer of 2007, using a 244-kHz Reson 8101 multibeam echosounder. 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 sediment type. 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).本数据集为SIM 3261中加利福尼亚州卡平特里亚近海制图区部分声散射图（acoustic-backscatter map，详见SIM 3261第3幅图）的数据内容。栅格数据文件包含于"BackscatterA_CSUMB_OffshoreCarpinteria.zip"压缩包内，可通过以下链接获取：http://pubs.usgs.gov/ds/781/OffshoreCarpinteria/data_catalog_OffshoreCarpinteria.html。 加利福尼亚州卡平特里亚近海制图区的声散射图数据，源自加州州立大学蒙特雷湾分校海底测绘实验室（CSUMB）与美国地质调查局（USGS）采集的反向散射数据。本元数据用于描述由CSUMB采集、经USGS重新处理的声散射数据。如需了解USGS采集的声散射数据详情，请参阅"BackscatterB_USGS_OffshoreCarpinteria_metadata.txt"元数据文件。 2007年夏季，CSUMB采用244-kHz Reson 8101多波束测深仪，完成了卡平特里亚近海东南部近岸与陆架区，以及西部陆架中部区域的测绘工作。 在声散射影像中，色调越亮代表反向散射强度越高，色调越暗则代表反向散射强度越低。反向散射强度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，可用于大致表征海底纹理与沉积物类型。 反向散射强度受多种因素影响，包括声源级、海底成像所用声波频率、掠射角、海底组成与特征（如粒径、含水量、体积密度及海底粗糙度）以及部分生物覆盖物。 坚硬且粗糙的海底类型（如岩石露头或粗粒沉积物）通常会产生更强的散射强度（高反向散射，对应亮色调）；而柔软的海底类型（如细粒沉积物）则会产生较弱的散射强度（低反向散射，对应暗色调）。