Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with underwater video camera, still camera and lights. Camera sled deployments were conducted during the day, from the contracted vessel Bonavista II. Data were collected in American Samoa, around the islands of Ofu and Olosega to support Benthic Habitat Mapping efforts from November 2-12, 2012.
These data provide optical observations that will be correlated with bathymetry and acoustic backscatter imagery to develop a benthic habitat map of Ofu and Olosega. Refer to supplemental information for description of instrument and survey.
Ofu and Olosega Islands are part of the Manu'a Island group in American Samoa, situated approximately 100 km northeast of Tutuila and 20km west of Ta'u. Centered at 14.17 degress S, 169.65 degrees W, the twin islands have very little human settlement. Ofu and Olosega are steep, volcanic high islands that lie only 75 m apart and are connected by a bridge and road built across the shallow reef flat. Shallow multibeam mapping was conducted in 2004 and revealed approximately 60 km2 of previously uncharted bank top (less than 300 m) that extends 0.2 to 2 km from shore and then drops abruptly to oceanic depths. An underwater portion of the National Park of American Samoa, which has exceptionally prolific coral growth, is located on the south shore of Ofu Island. Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with underwater video and still camera and lights. These data are used to provide ground-truth validation for benthic habitat maps based on multibeam echosounder surveys. Camera sled deployments were conducted during the day. The duration of each tow varied but averaged about 20 minutes of bottom time at a given location. The camera sled was deployed from a pot-hauler, mounted on the starboard aft of the vessel. The camera sled was lowered slowly to the seafloor by paying out cable, and once close to the seafloor, an altitude of 1-2 m was maintained by making adjustments on the length of cable out, using a remote pot-hauler switch, which allowed the operator to monitor a live video feed of the seafloor during operations. A second operator monitored the live video feed, and recorded real-time scientific observations, as well as any comments upon the operation, on a paper logsheet. Equipment Description: The TOAD sled consisted of a modified Phantom ROV body with a tail piece added for stability. It was equipped with a Deep Sea Power and Light Multi SeaCam 2060 color video camera, oriented approximately 45 degrees to the seafloor to provide a view of the seafloor as well as some view of upcoming obstacles. The sled was also fitted with a downward facing digital still camera (Ocean Imaging System DSC12000, consisting of Nikon D90 dSLR with Nikkor 20mm F/2.8 lens), and two 50 W DeepSea Power and Light LED lights (one to illuminate the video and one the still camera). Scaling of the digital still photographs was provided by a pair of Deep Sea Power and Light SeaLaster 100 parallel lasers, mounted 10 cm apart. The sled was also fitted with a Tritech PA200 altimeter, and an electronics bottle containing a compass, and depth sensor. Power to the sled, and video and data feed from the sled was conducted via a 16mm, 150 m long coaxial cable, connected to a topside control unit. An on-screen display unit was used to overlay time, date, depth and altitude onto the video footage. Name & address of person collecting data: John Rooney NOAA IRC NMFS/PIFSC/CRED 1845 WASP Blvd., Building 176 Honolulu, HI 96818 Data Files: Video data were recorded to miniDV tapes, and then backed up to DVD. Still images were saved to the camera's SD card and then backed up to external hard drive. Hypack 2012 hydrographic software was used to record time, vessel GPS position, camera sled altitude and depth, and length of cable out (entered manually). During deployments instantaneous layback calculations were performed by Hypack, using these data, and including the measured xyz offset between the vessel GPS antenna and the pot-hauler. File naming convention: Each tow is given a name consisting of a three-letter designator for the island area, followed by a two-digit year and a three-digit tow number, which increments by one for each new tow around that island. For example, during SB1216 (the 16th cruise in the calendar year 2012) the first tow was called OFU12001. For subsequent cruises in the same year, the tow numbers will increment by 100, so the first tow on the next cruise to Ofu in 2012 will be tow number OFU12100. Video tape labels and paper log forms are also annotated with the tow name; if more than one tape is required for a tow, consecutive letters are added to the end of the tow number (OFU01200a, OFU12100b, OFU12100c...). Navigation files generated by Hypack Max follow the Hypack CHS filename format consisting of the year, the first two letters of the platform name, the Julian date, and the hour and minute in which the file was started, followed by the extension .raw. For example, a file begun at 1935 on Dec. 10, 2004 (Julian date 345) aboard the Carolinian would be 2004CA3451935.raw. Time Correlation: All clocks were synchronized to UTC at the beginning of each day's operations. Two clocks were manually synchronized to GPS-derived times: the acquisition computer clock and the internal clock of the OSD-79 on-screen display unit. Resource Description: Digital video and still imagery that is geo-referenced to navigation files.
ground condition
Please acknowledge the NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center as the source of this information.
NOAA IRC
NMFS/PIFSC/CRED
1845 WASP Blvd., Building 176
e-mail preferred
Pacific Island Benthic Habitat Mapping Center, Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), NOAA
Unspecified
Complete
Hypack 2012 includes a window for manual entry of the length of camera sled cable paid out, a utility to enter horizontal and vertical offsets between the GPS antenna and sheave over which the camera sled cable passes, and a built-in caternary function. Using these data, Hypack 2012 automatically estimates the camera sled's position. Analysis of tow data indicate that horizontal positional uncertainty associated with the location of the camera sled recorded in Hypack is plus or minus 13 m.
After a tow was completed the video tape data was reviewed by spot-checking the master and backup tape to verify that data were recorded. Raw data files recorded using Hypack include time, horizontal position, depth information and altitude, and were copied from the acquisition computer to the data archive. During this cruise it was possible to export sled altitude from Hypack. Tow-specific metadata were recorded in the data archive in the same location as the raw data, in a spreadsheet that was then referred to in creating metadata records of each island where data were collected during the cruise. Raw data files were exported from Hypack as comma-delimited text files, and following additional processing were imported into a custom Access Database for imagery classification. The benthic habitat for each tow was classified using the PIBHMC_tow classification scheme. Five points were classified at 30 second intervals along the video and codes were inputted directly into the TOAD database. The classified results were then imported into ArcGIS v10.1, and then saved as a shapefile. Percent scleractinian coral was color-symbolized in optical validation maps. Additional attributes include metadata for each point, and the full results of the benthic classification. For more information on classificiation methods, refer to the PIBHMC website: ftp://ftp.soest.hawaii.edu/pibhmc/website/webdocs/documentation/Optical-Proc-Overview.pdf For more information on the classification scheme,refer to the PIBHMC website: ftp://ftp.soest.hawaii.edu/pibhmc/website/webdocs/documentation/Benth-Habitat-Class-Codes.htm
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These data are not to be used for navigational purposes. NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.
Each comma-delimited record contains the UTC date and time, latitude, longitude, altitude, vehicle depth, and water depth. List of navigation files: The shapefiles showing camera sled tracks listed below consist of a collection of files, followed by these extensions: .dbf, .shp, .shx, and .prj. All file types are necessary to properly displaying the source data. OFU12001-065 (65 files)
