Video transects of the sea floor on Stellwagen Bank during U.S. Geological Survey field activity 2016-004-FA, aboard the R/V Auk, January 28, 2016

Seabed videos were collected using two battery-operated, high-definition (1920 x 1080 pixels) GoPro Hero 4 Black digital video cameras mounted on the SEABOSS. See the cross-references for additional description of the SEABOSS system. The SEABOSS system had two GoPro cameras and a SeaViewer 6000 HD Sea-Drop video camera attached to it. The SeaViewer camera had a live feed to the surface and was used only to observe obstacles, like gill nets and lobster gear, in order to avoid entanglement. One of the GoPro cameras was the primary video acquisition camera and in case of camera failure, the additional cameras provided backup video.
As the SEABOSS drifted over the seabed, the GoPro cameras imaged the seabed at a rate of 60 frames per second from an altitude of ~1 meter. Lighting was provided by two, battery-operated Keldan LED video lights. Each light provided a light flux of up to 9000 lumens at a correlated color temperature of 5000 kelvins. Two parallel red lasers mounted 20 centimeters apart provided a scale in the video images.
Video imagery includes the launch and recovery of the SEABOSS, transit through the water column, and the drift over the seabed. The duration of individual video files ranges from 3.3 to 5.6 minutes. Video files are archived in .MP4 format and range in size from 0.8 to 1.3 gigabytes.
These video files are not available as part of this data release. Video files are archived at the USGS Woods Hole Coastal and Marine Science Center, 384 Woods Hole Road, Woods Hole, MA 02543.
The position (latitude and longitude) and time of the start of the video drift was recorded from the navigation receiver by hand in the log book when the SEABOSS reached the seabed and when it left the seabed. Latitude and longitude positions recorded by hand in the log book were later adjusted to match the data recorded in the GPS navigation file based on time. Video was recorded during the descent through the water column (1-2 minutes), during the drift over the seabed, and during the ascent.

The original raw $GPGGA navigation was run through an AWK script (awkauk_rndissue.gpgga, on a machine running Cygwin - www.cygwin.com) to reformat the latitudes and longitudes into decimal degrees and output the data into a comma-delimited text file with the following columns of information: latitude (decimal degrees out to five decimal places), longitude (decimal degrees out to five decimal places), hour, minute, second, Julian day, and year. The Julian day was determined by the original date in the filename of the navigation file as the GPGGA string does not contain any date information. The script made sure to round the latitude and longitude values to five decimal places in the same way that Excel would round the values. The AWK script also made sure that there were no duplicate records in terms of time, such as two navigation points recorded at 16:38:23. Depending on the boat drift rate, navigation fixes carried out to only five decimal places could have duplicate fixes. The individual navigation files were concatenated into a single file in order of acquisition. This process step and the remaining process steps were performed by the same person, VeeAnn A. Cross.

Another AWK script (awkdrift_pullstartend) was run on the stations summary CSV file to extract the following columns of information: station, Julian day of video start, Coordinated Universal Time (UTC) time of video start, Julian day of video end, UTC time of video end, and year.

A Python script (driftlog_gui_v5.py) run from Python IDLE version 2.7.14 on Windows 10 was used to extract all the navigation points from the navigation file based on the start and end time of the video drift and combine these into polylines. Ideally, there is a match of the same time (with a corresponding navigation fix) in the GPS file to the start and end video times recorded in the log book. However, if this situation does not exist, then the closest (in time) navigation record to the start and end time of the video transect is used, along with all the navigation points in between those two times. These extracted points were then combined into a polyline shapefile. The resulting shapefile has a polyline for every video drift. Based on the navigation system, the coordinate system of the dataset was set to geographic coordinates, WGS 84.