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 in the Commonwealth of the Northern Mariana Islands (CNMI), around 18 different islands and banks, to support Benthic Habitat Mapping efforts during NOAA Ship Oscar Elton Sette cruise OES0307, from August 22 through September 21, 2003.
These data provide optical observations that will be correlated with bathymetry and acoustic backscatter imagery to develop a benthic habitat map of the island of Saipan. Refer to supplemental information for description of instrument and survey.
Saipan, the largest of the Northern Mariana Islands, has a land area of 122 square kilometers and is approximately 20 km long and 9 km wide. The island consists of a volcanic core enveloped by younger coral reef-derived limestone formations. Saipan has the most diverse types of coral reefs and associated habitats of all the islands and banks in the Commonwealth. A fringing and barrier reef system protects the majority of the beaches along the western shore and coastal plains. The western side of the island is the most populated and the coral reefs along these areas are negatively affected by human activity. Continuing sediment and nutrient pollution combined with sporadic stressors such as outbreaks of crown-of-thorns starfish (Acanthaster planci) and temperature-induced bleaching affect many of Saipan's western and southeastern reefs. Furthermore, coral habitat on two large offshore banks (18 km x 22 km) in water depths between 30 m and 60 m on the western side of Saipan are negatively affected by the anchorage of commercial and naval vessels. 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 & 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 2, black in color) with an internal kevlar strength member to support the sled frame. The cable was led from the camera sled over a 22-inch diameter sheave hung from the J-frame, and from there around a gypsy head mounted on the alternate CTD winch, amidships on the vessel's port side. All TOAD surface components were located in the Dry Lab in an equipment rack on the after bulkhead. 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 3-letter designator for the island area followed by a two-digit year and three-digit tow number, which increments by one for each new tow around that island. For Saipan the designator is "SAI."During OES0307 (NOAA Ship Oscar Elton Sette's 7th cruise in calendar year 2003) the consecutive numbers started at SAI03001. Video tape labels, the navigation files (*.glo) and paper log forms are annotated with the tow name and number, e.g., SAI03002. If the navigation file is edited during processing the file name has a suffix 'a' added. For example, for a navigation data file named "SAI03002a.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, 'SAI03002a.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.
ground condition
Please acknowledge the NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center as the source of this information.
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NMFS/PIFSC/CRED
1845 WASP Blvd., Building 176
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Pacific Islands Benthic Habitat Mapping Center, Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), NOAA
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The horizontal position accuracy for the camera sled position is estimated at plus or minus 100 meters. There are three 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 used; no attempt is made to translocate this position to that of the tow block from which the camera is deployed. The difference between the tow block and the antenna is about 14 meters. The largest source of error is uncertainty associated with the sled's position relative to the tow block.
After a tow was completed the video tape data and still photographs were reviewed by spot-checking to verify that data were recorded. Navigation data were copied from the acquisition computer to the data archive. A metadata extractor (gloMeta.py, version 9/28/04) was run to summarize the navigation data and test for errors. If errors were detected they were corrected or flagged as appropriate and a new data file was made. This file's header was updated to document what type of processing occurred. A metadata file was recorded in the data archive in the same location as the navigation data. Processed navigation data were then read into ArcView 3.2 shapefiles using an Avenue script named `toadimport.playback.ave', version 9/25/01, written by Ronald Hoeke. The benthic habitat for each tow was classified using the PIBHMC_tow classification scheme. Five points were classified at 30 second intervals and codes were inputted into a spreadsheet, which was subsequently converted into an Acceess database containing all classified data for all islands. The classified results were then exported as an excel spreadsheet and imported into ArcGIS v9.3, and then saved as a shapefile. Percent scleractinian coral was column symbolized in Optical Validation maps with underlying fields of different substrates contained within the attribute table of the shapefile. For more information on classification methods, refer to the PIBHMC website ftp://ftp.soest.hawaii.edu/pibhmc/website/webdocs/documentation/Optical-Proc-Overview.pdf For more information on the classification scheme, refer to the PIBHMC website ftp://ftp.soest.hawaii.edu/pibhmc/website/webdocs/documentation/Benth-Habitat-Class-Codes.htm
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.
Navigation information are recorded as successive lines in a comma-delimited ASCII text file, with a .glo extension. Each line of a GLO file includes the following data: the year, day of year, time, latitude, longitude, water column depth, vehicle depth, layback, and wing angle. The field for wing angle does not contain useful data. A total of 13 navigation files were collected, including: sai03001.glo sai03002.glo sai03003.glo sai03004.glo sai03005.glo sai03006.glo sai03008.glo sai03009.glo sai03010.glo sai03011.glo sai03012.glo sai03013.glo sai03014.glo
These data were recorded on 7 video tapes, include 4 hours and 29 min of video data covering 3.0 linear km of seabed. List of video tapes: SAI03001-002, VHS, Master SAI03003-006, VHS, Master SAI03001-002, Mini DV, Master SAI03003-005a, Mini DV, Master SAI03005b-006, Mini DV, Master SAI03008-009, Mini DV, Master SAI03010, Mini DV, Master SAI03011-013, Mini DV, Master SAI03014, Mini DV, Master SAI03001-002, Mini DV, Backup SAI03003-005a, Mini DV, Backup SAI03005b-006, Mini DV, Backup SAI03008-009, Mini DV, Backup SAI03010, Mini DV, Backup SAI03011-013, Mini DV, Backup SAI03014, Mini DV, Backup
69 still images available; poor photos were enhanced or deleted List of photo folders: SAI03003: SAI_082303_0934 (27 photos) SAI03004: SAI_082303_1014 (34 photos) SAI03005: SAI_082303_1051 (8 photos)
