NANA1M.TIF - Anacapa Island Reserve sidescan sonar backscatter image in nearshore Benthic Habitat mapping Project S. California map Series. (UTM 10N, NAD83)

The sidescan sonar image of the nearshore seafloor (0 to 100 m water depths) of the Big Sycamore reserve area was mosaicked from data collected in 1998. A Klein 2000 sidescan system was used for geophysical surveying. A Triton Elics Isis brand side-scan data recording system was used on the cruise. The 1998 survey was navigated with a Leica Differential Global Positioning System (DGPS) which provided a ship position with accuracy of 1-5 m in DGPS mode. At times during the cruise differential signal was interrupted. In non-differential mode, the receiver provided a position with 30-50 m accuracy. A KVH Industries Inc. azimuth digital gyro-compass provided ship headings with 0.5 degree accuracy. Navigation data were recorded using Yo-Nav version 1.19 (Gann, 1992). The sidescan fish was towed approximately 30 m above the seafloor. The distance of the fish behind the ship was not known during this survey and must be estimated when the data are processed in order to produce the sidescan image mosaics. The resolution of the processed data mosaics is 0.2 m. The data are presented here at a resolution of 1 m. This is one of a collection of digital files of a geographic information system of spatially referenced data related to the USGS Coastal and Marine Geology Program Nearshore Benthic Habitat Mapping Project. See <http://walrus.wr.usgs.gov/nearshorehab> for more information.

本数据集为1998年采集数据拼接生成的大西克莫保护区（Big Sycamore Reserve Area）水深0至100米近岸海底侧扫声呐图像镶嵌图。本次地球物理勘测采用Klein 2000型侧扫声呐系统，航次作业中使用了Triton Elics Isis品牌侧扫数据记录系统。1998年勘测采用徕卡差分全球定位系统（Leica Differential Global Positioning System, DGPS）进行导航，该系统在差分工作模式下可提供1至5米精度的船舶位置数据；航次作业期间，差分信号曾多次中断，在非差分模式下，接收机提供的位置数据精度为30至50米。KVH工业公司（KVH Industries Inc.）的方位数字陀螺罗盘可为船舶提供0.5度精度的航向数据，导航数据通过Yo-Nav 1.19版本软件（Gann, 1992）进行记录。侧扫声呐拖鱼距海底约30米，本次勘测期间未记录拖鱼与船舶之间的拖曳距离，在后期处理生成侧扫图像镶嵌图时，需对该距离进行估算。处理后的数据镶嵌图原始分辨率为0.2米，本次公开的数据采用1米分辨率进行展示。本数据集是与美国地质调查局（USGS）海岸与海洋地质项目近岸底栖生境制图项目相关的空间参考地理信息系统数字文件集合之一。更多信息可访问<http://walrus.wr.usgs.gov/nearshorehab>。