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

These seafloor bottom photos 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 Shotcut video editor was then used to extract frame grab still images after identifying the best image of the seafloor. These still images are in JPEG format. An exiftool script was later used to add the location to each still image file. 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 photos 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 in the EXIF header 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).