ATRIS: Boat-Mounted, Georeferenced, Digital Imaging System

Schematic showing the ATRIS system. [Enlargement]

Ecologists and managers require highly detailed and accurately geo-located benthic-substrate observations for the monitoring and mapping of coral reef ecosystems. To meet this need, the U.S. Geological Survey has developed the Along Track Reef Imaging System (ATRIS), a boat-mounted instrument that acquires continuous digital still images of shallow-marine substrates.

Images are acquired via a high-speed (up to 30 frames/s) digital still camera mounted in a waterproof housing that is deployed on a pole attached to a survey vessel. Images are instantaneously transferred to a shipboard computer and stored on a bank of hard drives whose total capacity of more than half a terabyte eliminates any practical constraint on the duration of daily survey operations. Position and acquisition time obtained from a precision Wide Area Augmentation System (WAAS)-capable Global Positioning System (GPS) location receiver is saved in a binary file that accompanies each image. Accurate geo-positioning is also determined in post-processing software with dual-frequency carrier-phase differential GPS measurements from the boat made relative to a GPS base station at a nearby location. Simultaneously, navigation software in a separate computer is used to follow pre-planned transect lines and to collect a continuous log of the vessel's position.

Instantaneous camera-to-seafloor ranges acquired by a precision bathymetric sounder are captured that can provide scaling information for each image as well as submerged topography along the track line. A forward-looking underwater video camera provides an oblique view of the approaching bottom to the survey operator on a separate monitor. Open-source Linux PC software written for ATRIS datasets allows the interactive geographic browsing, scaling, and extraction of specific substrate images for further quantitative analysis. The ATRIS Data Analysis and Processing Tool (ADAPT) also includes a Classification tool that allows the user to define and classify the substrate for each image.

Operation of the ATRIS instrumentation requires a minimum crew of two people – a boat captain to navigate the vessel, and an instrument operator to adjust the pole length as required. An optional third crewmember can help in assessing the integrity of the data captured during the survey. The ATRIS sensor, with the digital still camera has been operational since Fall 2004, and been used primarily to study sea grass beds at the Terra Ceia Aquatic Preserve in Tampa Bay, Florida, and coral reef environments in Biscayne National Park, Dry Tortugas National Park, Florida, and along the fringing reefs of the island of Tobago.

The USGS seeks to develop partnerships to test the application of the ATRIS in diverse coastal-marine environments throughout the Caribbean region. For more information, contact Amar Nayegandhi.

Sample images acquired by ATRIS

Select individual images to view the larger version.

(1) Hard or stony coral	(2) A star coral on a largely rocky substrate	(3) Soft 'finger' corals
(4) Dense mixed corals	(5) Star coral surrounded by macroalgae	(6) Gorgonians and soft corals
Sample images acquired by ATRIS at Dry Tortugas National Park (DRTO), Florida. The high-resolution underwater imagery of the sea floor depicts various types of reef substrates at DRTO. The reef substrates as seen in the images: (1) hard or stony coral (2) a star coral on a largely rocky substrate, (3) soft 'finger' corals, (4) dense mixed corals, (5) star coral surrounded by macroalgae, (6) gorgonians and soft corals.