Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with underwater video camera, still 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 TOAD was deployed from a pot hauler mounted on the starboard side of the fantail on NOAA Ship Townsend Cromwell. It was lowered slowly to the bottom by the deck crew with the use of a capstan. The TOAD 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 TOAD was a MiniBat 8820 unit manufactured by Guideline, and was towed by the ship at 1-2 knots while remotely guided from the ship using adjustable wing controls to keep the unit close to the underwater substrate. Equipment Description: The TOAD is a camera sled based on the Guildline MiniBat model 8820 tow body. The frame was configured with a single Sony DCR-PC110 Digital Video Camera in a modified Gates underwater housing, a Canon Power Shot G1 Still Camera (modified by CRED engineers) in an Ikelite housing rated to 60 m slaved to an Ikelite DS-50 strobe, and two 500 W DeepSea Power & Light model 710-0400601 underwater lights. The Canon camera had a custom-built timer that enabled the user to select a constant time interval (ranging from approximately 5 seconds to 2 minutes) between photographs. An interval of 30 seconds was typically selected, which, assuming a mean velocity for the camera sled of 1.5 knots, resulted in one photograph approximately every 20 m. Photograph resolution is 2048 x 1536 pixels and file names are assigned sequentially and automatically by the camera, starting at 100-0000 after the camera's memory is cleared. The MiniBat pressure sensor and wing controller were also mounted on the frame but the pressure sensor was not operational. The cable between the sled and the surface was an underwater load-bearing electrical cable. The TOAD computers were located in the Electronics Lab of the Townsend Cromwell. The electronics box containing the power switches was secured to the ship's fantail, and all other TOAD surface components were secured in the ship's wet lab.
Name & address of person collecting data: Joyce Miller & Ronald Hoeke NOAA IRC NMFS/PIFSC/CRED 1845 WASP Blvd., Building 176 Honolulu, HI 96818
Data Files: Video data were recorded on two video tape recorders. Still photos were recorded on digital camera and downloaded to the TOAD computer after the tow. The position of the camera sled was recorded using Guildline MiniBat In-Tow data acquisition software.
File naming convention: Each tow is given a name consisting of a 3-letter designator for the island area, "SRW" in this case followed by a five-digit tow number. The first two digits indicate the last two digits of the calendar year, i.e., "01" is used for this cruise, which took place in 2001. The last three numbers indicate the consecutive number of the tow for that island and year, and start on the next hundred for subsequent cruises in that year to the same island. During TC0110 the consecutive numbers started at 001. Video tape labels, the navigation files (*.glo) and paper log forms are all annotated with the tow name. 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, "SRW01001.glo.met"
Time Correlation: All times are based on UTC. Two clocks were set manually synchronized prior to starting data collection; the clock in the video character generator that was used to annotate the video tape and the TOAD data acquisition computer clock was used to annotate the navigation (*.glo) files. These clocks were set to UTC at the beginning of each evening's operations and then compared to one another prior to (and during) each tow.
Resource Description: Digital video images geo-referenced to navigation files