Location map showing the 18 quadrangles in the Stellwagen Bank region.

Photograph-Collection Methods

SEABed Observation and Sampling System (SEABOSS) – As a part of the process of mapping the sea floor, the U.S. Geological Survey developed a photograph collection system to aid in the interpretation of seabed sonar imagery.

The SEABOSS is not a towed system. It incorporates a modified Van Veen sediment grab sampler, a still camera, and two color video cameras into a frame that is lowered to the seabed from a drifting vessel. A navigation receiver is placed on the ship at the location from where the SEABOSS is launched. The navigation system uses global positioning system (GPS) techniques, and locations of photographs are accurate to within 10 m. During deployment, the camera system hangs directly below the side of the ship, and the recorded navigation data closely approximate the position of the camera system near the seabed. The ship is oriented so that wind and waves will not cause it to drift over the conducting cable attached to the SEABOSS. The winch operator uses a video feed from the system to maintain the cameras at the proper height above the seabed; the scientist uses the video to decide when to trigger the still camera and record the time the photo was taken. The height of the camera above the seabed (76 cm; 30 in.) initially was determined by viewing an object hanging from the SEABOSS below the video camera; when the object touched the seabed, the camera height was appropriate for still photography. Later in the project, the camera height was determined by viewing a pattern of laser beams on the seabed. For further information on the SEABOSS, see

http://woodshole.er.usgs.gov/operations/sfmapping/seaboss.htm

https://pubs.usgs.gov/fs/fs142-00/fs142-00.pdf

Still-camera System – All photographic images were acquired with a Photosea underwater-camera system.

Photograph-Processing Methods

Photograph processing – Exposed film was developed in bulk 250-exposure rolls by a commercial film-processing company. The bulk rolls of negatives were then sent for scanning to a commercial digitizing company where the negatives were scanned by using Kodak Photo CD (PCD) software. A PCD image file of each negative was generated and archived on CD-ROM. PCD images can be used to generate images at resolutions ranging from 96 x 64 pixels to 3072 x 2048 pixels. The PCD images were converted to Joint Photographic Experts Group (JPEG) format. In this report, each image is available for downloading in two resolutions, a medium JPEG file (1536 x 1024 pixels) and a high-resolution JPEG file (3072 x 2048 pixels).

Image Information

Image characteristics - Each photographic image was taken at a height of approximately 76 cm (30 in.) above the seabed and represents an area of 0.39 m² (4.17 ft²) that measures 76 cm (30 in.) wide and 51 cm (20 in.) high. The data tag on the right-hand margin of the image displays information in the following format: NNNYYHHMM, where NNN is the image number on the film roll, YY is the last 2 digits of the year, and HH and MM are time in hours and minutes.

Metadata in Exchangeable Image File Format (EXIF) - Seabed photographs have been modified to an Exchangeable Image File Format so that important image metadata and data can be displayed in the comment EXIF tag of the JPEG images (see below).

Explanation of Metadata Tagged to Photographs in EXIF

Spreadsheets for photographic images - The navigation data for each photograph, as well as other information pertinent to each photograph such as date and time of collection, are available in the Data Catalog in both ESRI shapefile format with Federal Geographic Data Committee (FGDC) compliant metadata and Excel spreadsheet format. The Excel spreadsheet file is the source of the EXIF metadata displayed on the JPEG images for each quadrangle and is included in the folder containing the images for that quadrangle.

Explanation of Photograph Spreadsheet Columns

Vessel Names