Optical validation data were collected using a Tethered Optical Assessment Device (TOAD), an underwater sled equipped with an underwater digital video camera and lights. Data were collected at the Main Hawaiian Islands, around the island of Ni'ihau to support Benthic Habitat Mapping efforts.
These data provide optical observations that will be correlated with bathymetry and acoustic backscatter imagery to develop a benthic habitat map of Ni'ihau. Refer to supplemental information for description of instrument and survey.
Niihau, the oldest of the Main Hawaiian islands along with Kauai, is also the second smallest, at 182 sq. km, and the smallest inhabited Hawaiian island. Located at 21 degrees 55'N, 160 degrees 10'W, it is the furthest from the magma-producing hotspot which formed the island chain. The island lies only 21 km west-northwest of Kauai, but the islands are separated by a channel 1097 m deep. Niihau reaches a height of 390 m, has 72 km of shoreline, and an estimated reef area of 60 sq. km (Hawaii Coral Reef Network). The island is privately owned and was inhabited by 230 people in 1990. Like all of the Main Hawaiian islands, it is considered a high island and contributes significant nutrient and sediment runoff to coastal waters. Niihau has no designated marine protected areas. Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with underwater video camera and lights. These data are used to provide ground-truth validation that for benthic habitat maps based on multibeam echosounder surveys. Camera sled deployments were conducted at night, usually between 1800 and midnight. The duration of each tow varied but averaged about 40 minutes of bottom time at a given location. The camera sled was deployed from lower arm of the starboard J-frame on the NOAA Ship Hi'ialakai. 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 was lowered slowly to the bottom by the deck crew. The operator monitored a live video feed from the camera and began recording data on two video tape recorders. When the camera reached bottom the deck crew was notified by radio to stop lowering. The operator continued to monitor the vehicle and provided commands to raise or lower it to keep the camera just above the bottom. Equipment Description: The TOAD was deployed from the lower arm of the vessel's J-frame. The TOAD is a camera sled based on the Guildline MiniBat model 8820 tow body. The frame has been extensively modified from its original configuration and was equipped with an ROS model 54-00100-13 color underwater video camera as the primary data collection instrument. The ROS camera was mounted to point at approximately a 45 degree angle toward the seafloor. A Deep Sea Power and Light model 2050 MultiSeaCam low-light color video camera was also mounted on the sled and aimed straight ahead. The signal from this camera was fed to a second video monitor to provide warning of underwater obstructions the sled might be headed for. Illumination was provided by two 500 W DeepSea Power & Light Multi-SeaLite model 1050 underwater lights mounted on the original sled frame. The lights were located near the base and each side of the sled to provide the maximum possible horizontal distance from the ROS camera. An ORE Offshore model 4330B Multibeacon was attached to the sled to provide a response to acoustic interrogations sent by the Hi'ialakai's Model 4410D-01 Trackpoint II Plus Ultrashort Baseline acoustic tracking system. Cable between the sled and the surface consisted of a underwater electrical cable (cable 1, blue in color) with a separate load-bearing line to support the sled frame. The electrical cable was clipped to the line at regular intervals upon deployment and removed upon recovery. The load-bearing line was led to the starboard capstan on the aft deck. All TOAD surface components were located in the Dry Lab in an equipment rack on the after bulkhead. 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 video tape recorders. The position of the camera sled was recorded using Hypack Max version 02.012a survey software. File naming convention: Each tow is given a name consisting of a 3-letter designator for the island area followed by a two-digit year and three-digit tow number. During HI0505 the consecutive numbers started at OAH05000. 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 July 18, 2005 (Julian date 199) aboard the Hi'ialakai starting at time 1935 would be 2005HI1991935. Time Correlation: All times are based on UTC. Four clocks were manually synchronized prior to starting data collection; the clock in the video character generator that was used to annotate the video tape, in one of the video cassette recorders, in the Trackpoint II system, and in the computer running the Hypack Max software. These clocks were set to UTC at the beginning of each evening's operations. Resource Description: Digital video 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
The horizontal position accuracy for the camera sled position is estimated at plus or minus 60 meters. There are two primary sources of this error. The ship's positioning is based on GPS SPS, often called standalone or non-differential GPS positioning. SPS has a measured accuracy of under 5 meters. The position of the GPS antenna is referenced to the ship's granite block. The second and larger primary source of error is uncertainty associated with the sled's position as reported by the Trackpoint II acoustic tracking system, which is also referenced to the granite block.
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 Max software include time, horizontal position, and ship's heading information were copied from the acquisition computer to the data archive. 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 as comma-delimited text files which were then imported into ArcGIS v8.3 and saved as shapefiles.
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 information on the UTC date and time, horizontal position of the sled, and heading of the ship over the period of time that the camera sled is in the water. List of navigation files: 2005HI1990526 2005HI1990626 2005HI1990835 2005HI1991029 2005HI2000628 2005HI2000814 2005HI2000959 2005HI2010431 2005HI2010644 2005HI2010847 2005HI2011116 2005HI2011319
10h 55 m of video data are available covering 18.6 km of seabed. These data were recorded on 13 video tapes List of video tapes: NII05000, Mini DV, Master and Backup NII05001, Mini DV, Master and Backup NII05002a, Mini DV, Master and Backup NII05002b, Mini DV, Master and Backup NII05003, Mini DV, Master and Backup NII05004, Mini DV, Master and Backup NII05005, Mini DV, Master and Backup NII05006, Mini DV, Master and Backup NII05007, Mini DV, Master and Backup NII05008, Mini DV, Master and Backup NII05009, Mini DV, Master and Backup NII05010, Mini DV, Master and Backup NII05011, Mini DV, Master and Backup
