Australia contains some of the largest living carbonate platforms on Earth, including the iconic Great Barrier Reef (GBR). However, much of the GBR shelf remains unmapped using modern echosounder techniques, and many of the 2000 plus shallow coral reefs are represented only as simple polygons on nautical charts or in GIS datasets.
Figure 1. ALOS satellite and scene
Satellite imagery is a vast untapped source that can supplement aerial and ship-collected bathymetry or depth data, providing high-resolution depth data for all the coral reefs and shallow coastal waters. For example, Landsat satellite imagery has been successfully used to extract bathymetry data in tropical reef environments for clear waters of less than 20 metres.
An alternative satellite source is AVNIR-2 hyperspectral imagery from the Japanese Advanced Land Observing Satellite (ALOS) satellite, which collects 4 spectral bands ranging from 0.42 to 0.89 micrometers in wavelength, at a pixel resolution of about 10 metres (Figure 1).
Figure 2. Lidar depth data for comparison
Ocean mapping scientists from Geoscience Australia (GA) and James Cook University (JCU) started a research pilot project in 2009 to test whether ALOS AVNIR-2 hyperspectral imagery can be used to extract bathymetry data from an area on the northern GBR shelf, where it coincides with existing lidar depth data coverage for validation (Figure 2).
The goals of the Satellite bathymetry of the GBR project were:
- To test whether ALSO AVNIR-2 hyperspectral imagery can be used to extract depth data using the Stumpf (2003) method; and
- To assess whether satellite depth data can be used as source data used for developing a regional-scale 3D map of the GBR.
The high-resolution 3D depth models could provide marine managers and scientists with further knowledge of the seabed shape and habitat structure of shallow coral reefs. Satellite imagery could provide environmental properties over large areas of shallow water that currently have no detailed survey data.
The images are currently being analysed by the project team and the Satellite bathymetry of the Great Barrier Reef project will continue to provide more detail about the results as the research pilot project unfolds.
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