BSYC1M.TIF - Big Sycamore Reserve sidescan sonar backscatter image in the Nearshore Benthic Habitat Mapping Project S. California map series. (UTM 11N, 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.

本数据集为大西克莫保护区近岸海底（水深0至100米）的侧扫声呐图像，其镶嵌拼接自1998年采集的实测数据。本次地球物理勘探采用Klein 2000型侧扫声呐系统，本次航次使用Triton Elics Isis品牌侧扫数据记录系统。1998年的勘探作业依托徕卡差分全球定位系统（Leica Differential Global Positioning System, DGPS）完成导航，差分模式下船舶定位精度可达1~5米；航次期间差分信号曾多次中断，非差分模式下接收机的定位精度为30~50米。KVH工业公司（KVH Industries Inc.）的方位数字陀螺罗盘可提供精度为0.5°的船舶航向数据，导航数据通过Yo-Nav 1.19版本（Gann, 1992）记录。侧扫声呐拖鱼被拖曳至海底上方约30米处，本次勘探未记录拖鱼与船舶之间的间距，需在后期数据处理阶段估算该间距，方可生成侧扫声呐图像镶嵌图。经处理的原始镶嵌数据分辨率为0.2米，本次公开的数据分辨率为1米。本数据集是美国地质调查局（USGS）海岸与海洋地质项目近岸底栖生境测绘项目的空间参考地理信息系统数字文件集合之一。更多相关信息可访问<http://walrus.wr.usgs.gov/nearshorehab>。