CRED Optical Validation Data in the Auau Channel, Hawaii, 2008 to Support Benthic Habitat Mapping

The Auau Channel, located between the islands of Maui and Lanai and also protected by Molokaito the north, and Kahoolawe to the south, is bounded by the latitudes 20.983 and 20.733 and the longitudes -156.633 and -156.858. Topography of the channel consists of solution basins and rims (ridges), sediment plains and reefpinnacles on the channel floor, which were subaerially exposed during late Quaternary lowstands of sea level. Holocene reef growth occurs as a thin veneer on topographic highs in the Channel. The Channel reaches depths of 140 m, however, the majority of the seafloor is between 55 m and 70 m deep. The Auau Channel has been documented toinclude abundant coral reefs at these depths, which are also known as mesophotic coral ecosystems. Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped withunderwater video camera and lights. These data are used to provide optical information for benthic habitat maps based on multibeam echosounder surveys and to gather additional information regarding benthic and fish communities. Camera sled deployments were conducted at night and during the day. The camera sled was deployed off the starboard J-frame aboard NOAA ship Oscar Elton Sette. The TOAD was lowered slowly to the bottom by a winch holding 360 m of cable and operated from a control station in the dry lab of the ship. At each station the ship was positioned with the wind on the starboard side and drifted downwind; occasional light turns were applied to the ship's screws if necessary to reduce the ship's motion. The TOAD operator monitored a live video feed from the camera and recorded data on a video tape recorder. Equipment Description:The TOAD sled body used for the data collection was constructed from a shortened Phantom ROV body with a tail piece added for stability.The frame has been extensively modified from its original configuration and was equipped with two Deep Sea Power and Light Multi SeaCam 2060 color video cameras. One camera was mounted to point at approximately a 45 degree angle toward the seafloor and was the primary data collection instrument. The second camera was aimed straight ahead and the signal from this camera was fed to a second video monitor to provide warning of underwater obstructions and for the survey of fish communites. The video signals from the sled were sent via coaxial conductors within a 315 m long and 19 mm diameter umbilical cable to a topside control unit. The cable between the sled and the surface included an internal strength member to support the sled frame.  The cable was paid out and recovered using a dedicated custom-built winch equipped with slip rings and powered by a 5 hp electric motor. The winch was controlled at the winch itself for sled deployments and recoveries. The rest of the time a remote controller located in the dry lab was used to enable the operator at the video console to adjust the sleds altitude. All TOAD surface components were located in the Dry Lab in an equipment rack on the after bulkhead. Illumination was provided by two 250 W DeepSea Power & Light Multi-SeaLite model 1050 underwater lights mounted on the sled frame. The lights were located on each side of the sled to provide the maximum possible horizontal distance from the camera. The sled was also equipped with a sonar altimeter to detect the height of the camera above the seafloor, a pair of parallel lasers to determine the size/scale of viewed objects, a compass to determine the sled heading and orientation, and a depth (pressure) sensor. Neither the altimeter nor the pressure transducer functioned reliably during this cruise. A Tcount cable counter recorded cable out values to locate the position of the camera sled from the ship.These values were unreliable and therefore the ships position and a standard layback were used to determine camera sled position. 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 on two MiniDV tape recorders.The position of the camera sled was recorded using Hypack Max survey software. File naming convention: Each tow is given a name consisting of a 3-letter designator for the island area followed by two-digit year and three-digit tow number. For example, during SE0807 (NOAA Ship Oscar Elton Sette's 7th cruise in calendar year 2008) the first tow was called MAI08001. Video tape labels and paper log forms are annotated with the tow name.  Data files recorded in Hypack software followed their 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. For example, a file collected on August 3, 2008 (Julian date 217) aboard the Oscar Elton Sette starting at time 1845 would be 2008SE2171845. Time Correlation: All times are based on UTC.  Three clocks were manually synchronized prior to starting data collection; the clock in the on screen display that was used to annotate the video tape, in one of the video cassette recorders, and in the computer running the Hypack Max software. These clocks are set to UTC at the beginning of each operation.

Resource Description: Digital video imagery that is geo-referenced to navigation files.