The effort and cost required to convert satellite Earth Observation (EO) data into meaningful geophysical variables has prevented the systematic analysis of all available observations. To overcome these problems, we utilise an integrated High Performance Computing and Data environment to rapidly process, restructure and analyse the Australian Landsat data archive. In this approach, the EO data are assigned to a common grid framework that spans the full geospatial and temporal extent of the observations – the EO Data Cube. This approach is pixel-based and incorporates geometric and spectral calibration and quality assurance of each Earth surface reflectance measurement. We demonstrate the utility of the approach with rapid time-series mapping of surface water across the entire Australian continent using 27 years of continuous, 25 m resolution observations. Our preliminary analysis of the Landsat archive shows how the EO Data Cube can effectively liberate high-resolution EO data from their complex sensor-specific data structures and revolutionise our ability to measure environmental change.
A research alliance between the Commonwealth Scientific and Industrial Research Organization and Geoscience Australia was established in relation to Digital Earth Australia, to develop a Synthetic Aperture Radar (SAR)-enabled Data Cube capability for Australia. This project has been developing SAR analysis ready data (ARD) products, including normalized radar backscatter (gamma nought, γ0), eigenvector-based dual-polarization decomposition and interferometric coherence, all generated from the European Space Agency (ESA) Sentinel-1 interferometric wide swath mode data available on the Copernicus Australasia Regional Data Hub. These are produced using the open source ESA SNAP toolbox. The processing workflows are described, along with a comparison of the γ0 backscatter and interferometric coherence ARD produced using SNAP and the proprietary software GAMMA. This comparison also evaluates the effects on γ0 backscatter due to variations related to: Near- and far-range look angles; SNAP’s default Shuttle Radar Topography Mission (SRTM) DEM and a refined Australia-wide DEM; as well as terrain. The agreement between SNAP and GAMMA is generally good, but also presents some systematic geometric and radiometric differences. The difference between SNAP’s default SRTM DEM and the refined DEM showed a small geometric shift along the radar view direction. The systematic geometric and radiometric issues detected can however be expected to have negligible effects on analysis, provided products from the two processors and two DEMs are used separately and not mixed within the same analysis. The results lead to the conclusion that the SNAP toolbox is suitable for producing the Sentinel-1 ARD products.
1 May 2006 in International Journal of Remote Sensing
Annular‐ to crescent‐shaped low backscatter SAR slicks over carbonate reefs and shoals in the Timor Sea that exhibit ‘feathering’, and within the coral spawning period for the region, are interpreted to be caused by a coral spawn event. This represents the first time that such an event has been interpreted through satellite remote sensing. Additionally, ocean current data and detailed swath bathymetry of the sea floor to the south‐east of the coral spawn slicks suggest that elongate repeating slicks in this area are related to current flow over submarine channels. Assessment of these slicks in association with ancillary data, such as bathymetry, current velocities, weather, and timing of SAR acquisition allow a more robust interpretation of their origins. Through differentiating coral spawn and bathymetric slicks from oil and other biological slicks in shallow carbonate systems, such as the Timor Sea, petroleum and environmental assessments for these areas can be improved.
Geoscience Australia is implementing the geospatial component of the Australian Geophysical Observing System (AGOS). AGOS infrastructure will include a network of radar corner reflectors, in addition to a geodetic ground mark network for monitoring ground deformation in Australia. In this paper we describe the design of radar corner reflectors for deformation studies and calibration of Synthetic Aperture Radar (SAR) sensors. Through a prototyping campaign in 2013 we will seek a single reflector design that can be used for deformation and calibration studies using X- and C-band SAR sensors. Prototyping will involve precise determination of reflector radar cross section at an outdoor radar test range and a temporary field deployment in the Canberra region during which X- and C-band data acquisitions will be made from orbiting SAR satellites. We also outline plans to deploy corner reflectors in the Surat Basin of Queensland to monitor ground deformation induced by coal seam gas (CSG) extraction.