LIS phase 2 LDEO sediment grab bottom videos (2017, 2018)

These seafloor bottom video clips were collected as part of the Long Island Sound mapping phase 2 project. During three surveys in 2017 and 2018 aboard the research vessels Pritchard and Seawolf, a GoPro Hero 6 video camera was mounted on the frame of a sediment grab device. The camera was set to record video during the sediment sampling operations. The videos were processed using open-source Shotcut software (www.shotcut.org). The videos were clipped to focus upon the time that the sediment grab was close to the seafloor. These video clips are in MP4 format. Still images extracted as frame grabs from these videos are available as a related data set. During the first survey, in 2017, the camera was deployed without external lights and the image was dark below water depths of 8-10m. As result there are some grab stations for which no usable bottom videos exists. For the later surveys, external artificial lights were deployed (Sola video lights, model 3800). These lights allowed video images to be collected in deeper waters. The location of each JPEG image was tagged with the coordinate information for the corresponding sediment grab station. Location information is based on DGPS navigation using the ship GPS antenna. Lateral offset between the ship GPS antenna and the grab sampling device, and drift of the grab sampling device in the water, have not been corrected. The resulting uncertainty in true position could be on the order of 5-10m. Funding was provided by the Long Island Sound Mapping Fund administered cooperatively by the EPA Long Island Sound Study and the Connecticut Department of Energy and Environmental Protection (DEEP).本海底底栖视频片段采集自长岛海峡（Long Island Sound）二期测绘项目。2017至2018年间，研究团队依托“普里查德号”（Pritchard）与“海狼号”（Seawolf）两艘科考船开展了三次科考作业，将GoPro Hero 6型摄像机安装于沉积物采泥器（sediment grab device）的支架之上，设置为在沉积物取样作业过程中同步录制视频。所有视频均通过开源Shotcut软件（www.shotcut.org）进行后期处理，并经剪辑仅保留沉积物采泥器接近海底的时段内容，最终生成的视频片段均采用MP4格式。从上述视频中提取的帧截图静态图像，已作为关联数据集同步发布。2017年的首次科考作业中，摄像机未配备外置照明设备，水深8-10米以下区域的拍摄画面会出现严重暗化，导致部分取样站位无法获取可用的海底视频素材。后续科考作业中，团队加装了外置人工照明设备（Sola 3800型视频补光灯），使得深水区的海底视频采集得以实现。每张JPEG格式图像均已标记对应沉积物取样站位的坐标信息，坐标数据基于科考船GPS天线接收的差分GPS（DGPS）导航信号获取。但未对科考船GPS天线与采泥器装置之间的横向偏移，以及采泥器在水中的漂移量进行校正，因此真实位置的不确定性误差可达5至10米量级。本项目由美国环境保护署（EPA）长岛海峡研究项目与康涅狄格州能源与环境保护部（DEEP）联合管理的长岛海峡测绘基金提供资助。