CCB_SEABOSS_PHOTOS: Seafloor photographs (JPEG format) collected by the U.S. Geological Survey offshore of Massachusetts within northern Cape Cod Bay.

The JPEG photos alone do not represent spatial data, however the shapefile "CCB_BottomPhotos" records the filenames and geographic location of these photographs. Navigation for survey 07003 used differential Global Positioning System (GPS). The recorded position of each bottom photograph is actually the position of the GPS antenna on the survey vessel, not the SEABOSS sampler. The SEABOSS was deployed approximately 5 meters astern of the GPS antenna off the ship's J-frame on the starboard side. No layback or offset was applied to the recorded position. In addition to the +/-5 meter offset the SEABOSS may drift additionally away from the survey vessel when deployed to the seafloor. Based on the various sources for horizontal offsets, a conservative estimate the horizontal accuracy of the bottom photograph locations is 20-30 meters.

The SEABed Observation and Sampling System (SEABOSS) was designed by the U.S. Geological Survey (USGS) for rapid and effective collection of seabed images and sediment samples in coastal regions. The observations from video and still cameras and the sediment data are used to explore the nature of the seafloor and, in conjunction with high-resolution geophysical data, to make interpretive maps of sedimentary environments and validate the acoustic remote sensing data. The SEABOSS is a simple system that can be deployed from both small and large surface vessels and operates in water depths up to 200m. It incorporates two video cameras, a still camera, a depth sensor, and a modified Van Veen sediment sampler. The elements of this particular SEABOSS system are held within a stainless steel framework that measures 1.2 x 1.2 meters and weighs 136 kilograms overall. The frame has a stabilizer fin that orients the system as it drifts over the seabed. The digital camera, a Minolta DiMAGE A2, is mounted in a machined Delrin housing with a flat port and is set for 3264x2448 pixel images at the "fine" setting for compression. This allows the camera to be used for over 200 images with a 1 GB Compact Flash card without downloading. The system also has a PHOTOSEA strobe. Two lasers are set 20 cm apart (both as they are mounted on the SEABOSS frame and as seen in photographs and video on the seabed) for scale measurements. The red laser dots can usually be seen in the photo depending on the bottom type and the distance to the sea floor. A third laser is positioned at an angle so that when it intersects the other lasers, the SEABOSS is at the optimum height (approximately 75 cm) off the bottom for a still photograph. The camera is set to a manual focus and set to a default focus distance once the camera is powered up. The default focus distance is slightly less than the optimum height above the seafloor to account for optical distortion under water. All of the system's elements are powered from the surface vessel through a conducting cable. The winch operator views a video monitor so that the system can be maintained at an appropriate height above the bottom and obstacles can be avoided. Scientists also view video monitors and decide when to sample and take still photographs. Video displays include station number, water depth (from the depth sensor), and date, time, and geographic position (provided by a shipboard navigation system). The SEABOSS was deployed from the R/V Connecticut off the ship's J-frame on the starboard side. The vessel occupied one of the target stations and deployed the SEABOSS. The winch operator lowered the sampler until the seafloor was observed in the real-time bottom video. On most stations, the vessel and sampler drifted with wind and current for approximately 5-15 minutes. The SEABOSS operator monitored the real-time bottom video and acquired still bottom photographs at points of interest by remotely triggering the camera shutter. The number of photographs per station varied from 4-20 depending on the complexity of the bottom. The third laser on the system was set to an angle such that the optimum photograph height was 75 cm. The default focus on the camera was set to 50 cm. The imaged area is most often within 0.5 to 1.25 meters from left to right. Other camera settings are as follows: aperture is set at f/10; shutter speed is 1/250 second. The camera time during this survey was manually set to UTC, unless otherwise noted (see metadata for CCB_BottomPhotos.shp (http://pubs.usgs.gov/of/2010/1006/html/appendix1.html) for details on when the time value was wrong and how it was corrected). Time offsets were manually adjusted and verified by the SEABOSS video. The data and timestamp on the video is acquired directly from the GPS in UTC.

One hundred eighty-four target stations were occupied aboard the R/V Connecticut (USGS survey 07003) with the large SEABOSS (Blackwood and Parolski, 2001) that was equipped with a Van Veen grab sampler, a digital still camera, and a video camera.  A total 673 bottom photographs were collected at the 98 target stations within the Cape Cod Bay survey area.  JPEG photographs were acquired at each station.  The digital photographs were downloaded from the camera and backed-up to a laptop and hard-drive four times during the sampling survey. The JPEG photos alone do not represent spatial data, however the shapefile CCB_BottomPhotos.shp (also in this report, USGS OFR 2010-1006) makes the link between these photos and the navigation from USGS field activity 07003.  The link is possible because the JPEG photographs EXIF header records acquisition time. However, there were errors in setting the camera's clock; see metadata for CCB_BottomPhotos.shp for details on when the time value was wrong and how it was corrected.
Note: the EXIF headers contain the original (uncorrected) time stamps.

Image names repeated for each subsequent day therefore the original JPEG images were renamed from the sequential, camera automatic filename (i.e. PICT001.JPG) to a filename with the download number (1-4) appended to the filename (e.g. DL1_PICT001.JPG). For example, DL1 indicates the first download session.

JPEG photographs were resized to fit on the DVD Open-File Report using IrfanView (v4.23). The images were compressed using a save quality of 70 percent for the unzipped version of the files (found in the folder GIS\hyperlink_images\seaboss\07003). JPEG photographs were also resized to 1200x900 pixels and compressed with a save quality of 80 percent for the files in the zipped file CCB_BottomPhotos_JPEG.zip.  Note, this report contains SEABOSS JPEG images at 2 different resolutions; the zip file contains the lower resolution images to enable quicker and easier downloading for users accessing the online version of the report.