The Auau Channel, located between the islands of Maui and Lanai and also protected by Molokai
to 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 reef
pinnacles 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 to
include 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 with
underwater video camera and lights. These data are used to provide ground-truth validation for benthic habitat
maps based on multibeam echosounder surveys and to gather addictional information regarding benthic and fish communities.
Camera sled deployments were conducted at night, usually between 1800 and 600. The duration of each tow varied, but averaged
about 1 hour 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 a winch holding 360 m of cable and operated from a control station in the dry lab of the ship. The operator monitored a live
video feed from the camera and began recording data on two video tape recorders. 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 sled body used for the data collection was constructed from a shortened Phantom ROV body
with a tail piece added for stability.Â 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. Â 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.Â 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.
Name & address of person collecting data:
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 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 tow number. During HA0905 the consecutive numbers started at MAI09000. 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 Julian date, and the hour and minute in which the file was started. For example, a file collected on
July 26, 2009 (Julian date 207) starting at time 1055 would be 2009_2071055.
Time Correlation: All times are based on UTC. All clocks were manually synchronized prior to starting data
collection; the clock in the video character generator that was used to annotate the video tape, the clock in the
On Screen Display system, clocks in both MiniDV tape recorders, 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.