Bathymetric & Benthic Mapping

Along-Track Reef Imaging System

The project seeks to test the feasibility of combining field observations from an along-track vessel-mounted sensor package with IKONOS or QuickBird commercial satellite imagery to monitor and map in detail the bathymetry and benthic habitats of Buccoo Reef and other reefs that fringe Tobago.

The objective of the pilot project (Phase 1) is to collect high resolution bathymetric and along-track substrate imaging data sets to be made available to the THA for use establishing a coral reef monitoring program, and in the revision of existing bathymetric charts.

The U.S. Geological Survey (USGS) has developed the Along Track Reef Imaging System (ATRIS) to acquire continuous digital still images of the sea floor during transects across shallow water reefs for use in the creation of benthic habitat maps. EXIF-format still images are acquired in autonomous mode via a Nikon D1x digital still camera mounted in a waterproof housing that is deployed on a pole attached to the survey vessel. Images are instantaneously transferred to a shipboard computer. Position and acquisition time obtained from a precision Wide Area Augmentation System (WAAS)-capable GPS receiver is sent to the camera, where it is incorporated into the header files of the EXIF format images. At the same time, navigation software in a separate computer is used to follow pre-planned transect lines and/or to collect a continuous log of the vessel’s position, typically at a one second rate. The GPS antenna is mounted on top of the camera pole, and accordingly the positions recorded are those of the camera as the images are acquired. A precision bathymetric sounder is mounted to the bottom of the camera pole continuously measures the height of the camera above the bottom. This camera-to-substrate range information is recorded by the navigation software for use in post-processing to determine the scale and bottom coverage area of each individual image.

This study was supported by the Buccoo Reef Trust, the Tobago House of Assembly (THA), the U.S. Geological Survey Center for Coastal and Watershed Studies, and the National Coral Reef Institute.