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 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 the port J-frame mounted amidships on the NOAA Ship Oscar Elton Sette. At each station the ship was positioned with the wind on the port 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 using a capstan. The operator monitored a live video feed from the camera and began recording data on a video tape recorder. 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 port side 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 and 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. 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: Joyce Miller NOAA IRC NMFS/PIFSC/CRED 1845 WASP Blvd., Building 176 Honolulu, HI 96818
Data Files: Video data were recorded on a video tape recorder. The position of the camera sled was recorded in WGS-84 using Guildline MiniBat In-Tow data acquisition software and a data feed from a shipboard Northstar Chartplotter.
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. During OES0401 (NOAA Ship Oscar Elton Sette's 1st cruise in calendar year 2004) the consecutive tows at Howland started at HOW4000. For following cruises, the tow numbers will increment by 100, so the first tow on the next cruise to Howland in 2004 will be tow number HOW04100. Video tape labels, the navigation files (*.glo) and paper log forms are annotated with the tow name and number, e.g., HOW04012. If the navigation file is edited during processing the file name has a suffix 'a' added. For example, for a navigation data file named HOW04012a.glo, the 'a' would indicate that metadata were extracted from the navigation data and recorded to a file with the same name as the navigation file except that a file type of '.met' was appended; for example, 'HOW04012a.glo.met.
Time Correlation: All times are based on UTC. Two clocks were manually synchronized prior to starting data collection; the clock in the video character generator that was used to annotate the video tape, and the clock in the TOAD data acquisition computer. 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.
Online Links:
Pacific Island Benthic Habitat Mapping Center, Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), NOAA
These data provide optical observations that will be correlated with bathymetry and acoustic backscatter imagery to develop a benthic habitat map of Howland. Refer to supplemental information for description of instrument and survey.
Are there legal restrictions on access or use of the data?Access_Constraints: None
Use_Constraints:Please acknowledge the NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center as the source of this information.
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.
| Data format: | Each comma-delimited record contains information on the UTC date and time, latitude, longitude, velocity north and east of the ship, water depth of the seafloor below the transducer (to find the total depth from the water surface to the seafloor add 5 m to these values to account for the depth of the tranducer) layback, and wing angle. List of navigation files: The shapefiles showing camera sled tracks listed below consist of a collection of files with the names listed below, followed by these extensions: .dbf, .shp, .shx, and .prj. All file types are necessary to properly displaying the source data. List of Navigation Files: how04000a.glo how04001a.glo how04002a.glo how04003a.glo in format ASCII |
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| Media you can order: | CD-ROM (format ISO 9660) |
| Data format: | A total of 3 separate segments of video data are available. These data were recorded on 2 video tapes List of video tapes: HOW04000-002, VHS, Master HOW04003, VHS, Master HOW04000-002a, Mini DV, Master HOW04000-002b, Mini DV, Master HOW04003, Mini DV, Master HOW04000-002a, Mini DV, Backup HOW04000-002b, Mini DV, Backup HOW04003, Mini Dv, Backup in format VHS, miniDV |
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| Media you can order: | Video cassette tape (format VHS miniDV) |