SVAN1M.TIF - Point Agruello (South Vandenberg Reserve) sidescan sonar backscatter image in the 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.

大西克莫保护区近岸海底（水深0~100米）的侧扫声呐（sidescan sonar）镶嵌图像，由1998年采集的探测数据拼接生成。本次地球物理探测采用Klein 2000侧扫系统，科考航次搭载了Triton Elics Isis品牌侧扫数据记录系统。1998年探测航次采用徕卡差分全球定位系统（DGPS）进行导航，该系统在差分模式下的船舶定位精度为1~5米；航次期间差分信号曾多次中断，此时接收机切换至非差分模式，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为船舶提供0.5度精度的航向信息。导航数据通过Yo-Nav 1.19版本软件记录（Gann，1992）。侧扫拖鱼（sidescan fish）的作业高度约为海底上方30米，本次探测未记录拖鱼与船舶之间的间距，因此在后期处理生成侧扫声呐镶嵌图像时，需对该间距进行估算。经处理后的原始镶嵌数据分辨率为0.2米，本次发布的数据分辨率调整为1米。本数据集属于美国地质调查局（USGS）海岸与海洋地质项目近岸底栖生境制图项目的空间参考地理信息系统数字文件集合之一，详细信息可访问<http://walrus.wr.usgs.gov/nearshorehab>获取。