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.

本数据集为大西科莫保护区（Big Sycamore reserve area）水深0~100米的近岸海底侧扫声呐（sidescan sonar）镶嵌图像，其数据来源于1998年科考航次的采集成果。本次勘测采用Klein 2000型侧扫系统开展地球物理探测，航次同时搭载Triton Elics Isis品牌侧扫数据记录系统进行数据采集。1998年航次的导航系统为徕卡差分全球定位系统（DGPS），差分模式下可提供精度1~5米的船位数据；航次执行期间差分信号曾多次中断，非差分模式下接收机定位精度为30~50米。配套KVH工业公司（KVH Industries Inc.）的方位数字陀螺罗经，其测量的船艏向精度为0.5°。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（sidescan fish）的拖曳高度约为海底上方30米，但本次勘测未记录拖鱼与母船之间的相对距离，后续处理数据以生成侧扫声呐镶嵌图像时，需对该距离进行估算。处理后的原始数据镶嵌图分辨率为0.2米，本次公开的数据集分辨率为1米。本数据集属于与美国地质调查局（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>获取。