The laser line scan (LLS) systems utilize a sweeping blue-green laser to reflect light across the seafloor to generate a gray-scale image similar to a black and white photograph. Click image for larger view and image credit.
Operation Laser Line 2006
November 8 - 13, 2006
Mapping of coral reefs has been identified as one of the first and most important steps needed to address the increasing decline of the world’s coral reefs. Photography or direct observation is required to identify corals and other coral reef community organisms, but only small areas can be covered with these techniques. Laser line scanning has been suggested as an alternative method that can provide high-resolution imagery of the seafloor over a much wider area than conventional photography. Laser line scan (LLS) systems sweep a blue-green laser across the bottom and uses the reflected light to generate a gray-scale image of the seafloor that is similar to a black and white photography.
The NOAA Pacific Island Fisheries Science Center, in collaboration with partners from the NOAA Office of Ocean Exploration, the Hawaii Undersea Research Laboratory, the Hawaii Division of Aquatic Resources and the UH Botany Department will embark on a 6-day research cruise from November 8 – 13, 2006. The only commercially-available LLS system in the world will be deployed at a handful of sites off the coast of Maui. Expedition survey targets include beds of commercially-harvested black coral, a recently-discovered deep hard coral reef, an important nursery area and fishing site for commercially-harvested groundfish, deep algae beds, and a WWII aircraft wreck. This wide range of targets will enable us to thoroughly evaluate LLS technology, and hopefully provide the impetus to design less expensive and more capable LLS systems to meet management and research needs in coral reef ecosystems.
Mission Facts
- Although laser line scan (LLS) systems have been in existence for decades, there is only one system in the world, Scientific Applications International Corporation’s Northrop-Grumman SM-2000, which is commercially available.
- The SM-2000 LLS system uses blue-green laser light to image the ocean bottom. The combination of a blue-green light source, and laser light, enable the system to image objects at up to five times the range of conventional photography.
- LLS sends and receives the laser light by bouncing it off of two separate four-sided, pyramid-shaped rotating mirrors.
- The LLS system generates data so detailed that operators have captured images of individual crabs, strands of kelp, and even the Nike Swoosh logo on a shoe lying on the bottom.
- Deep algae beds being surveyed with the LLS during this expedition are composed of the endemic algae Halimeda kanaloana. In general, over 25% of Hawaiian reef organisms are endemic (found nowhere else in the world).
- The laser beam generated by the LLS moves along the seafloor at speeds on the order of 10 meters in a few milliseconds, or approximately 2 miles per hour.
- The deep scleractinian (stony) coral reef complex off Maui that will be surveyed during this expedition is among the deepest, and may in fact be the deepest reef with almost complete coverage of the seafloor by hard corals, in U.S. waters.
- Because the LLS system can be towed at much higher altitudes above the seafloor and doesn’t need the bright light systems typically found on ROVs, drop camera systems, etc. the LLS has a minimal impact on marine organism behavior. As a result of these characteristics, LLS technology appears to offer great promise as a means of accurately sampling populations of fish and other organisms that live on or near the seafloor.
- The entire LLS system requires two to three 20 ft shipping containers to hold all the equipment needed to install it on a research or survey vessel.
- Black corals in Hawaii are typically harvested by individual scuba divers who descend to depths of between 150 ft and 200 ft or deeper. They cut off black coral “trees” meeting the minimum size requirements with a hatchet and send bunches of black coral trees to the surface with lift bags. As their air runs low, they ride the last bag up to a depth of 60 ft or so to decompress. Many divers have been seriously injured or killed following this risky protocol.
Updates & Logs
Click images or links below for detailed mission logs and updates.
Mission Summary Although the mission did not go as planned, enough laser data was collected to evaluate the effectiveness of the laser line scanner in coral reef ecosystems.
Nov 20 The laser line scanner has been recovered from the bottom of the ocean.
Nov 13 The Laser Line team adapts to circumstances and begins underwater mapping off the Big Island.
Nov 11 For Chief Scientist John Rooney and the Laser Line team, high hopes have ended in disappointment.
Nov 10 "We lost the fish!" An accident leads to the loss of the laser line scanner.
Nov 9 The team tests the laser line scanner and creates near photographic maps of the seafloor and its inhabitants.
