Abstract
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.
Highlights
Three Synthetic Aperture Radar (SAR) analysis ready data (ARD) products have been developed for the Australian SAR Data Cube project due to their potential benefits in environmental and agricultural applications
ARD products are designed to use freely available SAR data with processing workflows based on open source software, in particular the Sentinel-1 SAR and the Sentinel Application Platform (SNAP) processing toolbox
To evaluate the quality of the SAR ARD products generated using the SNAP toolbox, they were compared to equivalent products generated from one of the industry-best proprietary software, GAMMA
Summary
Synthetic Aperture Radar (SAR) data have been shown to provide different and complementary information to the more common optical remote sensing data. ODC platforms [4] aim to enable easier access to satellite ARD, as they remove the need for the user to pre-process Earth observation datasets, and provide access to archived remotely sensed data in a format ready for use. SAR ARD products for Australia, which currently include radar backscatter (gamma nought, γ0 ), eigenvector-based dual-polarization decomposition and interferometric coherence, all generated from the Sentinel-1 IW swath mode data available through the Copernicus Australasia Regional Data. ARD products, selected scenes are processed to radar backscatter and interferometric coherence using the proprietary software GAMMA [9] for comparison. This manuscript first describes the three SAR ARD products being developed for the Australian. We evaluate the outputs from the SNAP toolbox and compare them to outputs from the proprietary GAMMA software
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