DEEP ATRIS - An Auto-adjusting, Towed, Digital Imaging System
Maps of coral ecosystems are needed to support many conservation and management objectives, as well as research activities. Examples include ground-truthing aerial and satellite imagery, characterizing essential habitat, assessing changes, and monitoring the progress of restoration efforts. To address some of these needs, the U.S. Geological Survey developed the Along-Track Reef-Imaging System (ATRIS), a boat-based sensor package for mapping shallow-water benthic environments (See ATRIS - boat-mounted, georeferenced, digital imaging system).
Deep ATRIS extends this functionality to depths of 27 m. The system is based on The Sea Sciences, Inc. Acrobat™ LTV-50, a light-weight, computer-controlled, towed vehicle that is capable of following a programmed diving profile. The vehicle is 81 cm long with a 63-cm wing span and can carry a wide variety of research instruments, including CTDs, fluorometers, transmissometers, and cameras. Deep ATRIS is currently equipped with a high-speed (20 frames/s) digital camera, custom-built light-emitting-diode lights, a compass, a 3-axis orientation sensor, and a nadir-looking altimeter.
| Specifications: |
| Dimensions (LxWxH) |
0.81 x 0.25 x 0.63 m |
| Wing span |
1.2 m |
| Weight (in air) |
45 kg |
| Operating Depth Range: |
3 – 27 (m) |
| Image size: |
1,360 x 1,024 pixels |
| Image capture: |
1 - 20 images/s |
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The vehicle dynamically adjusts its altitude to maintain a fixed height above the seafloor. The camera has a 29° x 22° field-of-view and captures color images that are 1360 x 1024 pixels in size. GPS coordinates are recorded for each image. A gigabit ethernet connection enables the images to be displayed and archived in real time on the surface computer. Deep ATRIS has a maximum tow speed of 2.6 m/s.
Only a modest amount of support equipment is needed to deploy Deep ATRIS. Typically, we use a 25' Oceans Formula boat with a tow bar to keep the cable away from the outboard motor and a standard sailboat winch to aid cable retrieval. A portable Honda generator powers the system and the computers.
Example Image Mosaics
Spatial resolutions of better than 3 mm/pixel are common. In most instances, taxonomic identification is possible at least to the genus level. Given this degree of detail, coupled with the coincident bathymetric and location data, Deep ATRIS imagery is more than adequate for ground-truthing acoustic and lidar data, as well as classifying habitats. It can be used to estimate a number of ecological parameters, such as percent cover, organism abundance, and species richness.
Animal Observations
Given that fish and sea turtles are seemingly unfazed by its presence, there are likely fisheries applications for Deep ATRIS.
For more information, contact Dr. Dave Zawada (dzawada@usgs.gov)
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