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Leo Lymburner and the DEA team

Explore Digital Earth Australia's vast Landsat archive, advanced ARD implementation, and powerful API for spatial, temporal, and spectral analysis. Access surface water dynamics, intertidal zone extent, and suspended sediment data, with upcoming wetlands and mangrove studies. Leverage geometric and radiometric accuracy, collaborate with global partners for in-situ measurements, and understand pixel quality flags for data screening. Discover the potential of configuring PQ flags and proposed global ARD specifications for automated processing.

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Leo Lymburner and the DEA team

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  1. Leo Lymburner and the DEA team

  2. Overview • What is Digital Earth Australia • All you wanted to know about Pixel Quality flags but were too afraid to ask

  3. What is Digital Earth Australia? • Australia’s Landsat archive (TM, ETM+ and OLI) • 1987-present • Terrain corrected, BRDF corrected surface reflectance • Per pixel quality flags • ACCA • Fmask • Per band saturation • In short – another continental scale ARD implementation

  4. API • Postgres database + Python API • API design • Band names (red rather than band 3) • Configurable PQ flags • Returns x-array object (multidimensional array with labelled dimensions) • Easy to perform spatial, temporal, spectral analysis • IDE via Jupyter notebooks on a virtual desktop • Scale up onto an HPC

  5. Open Data Cube • Collaboration between GA, CSIRO and NASA Systems Engineering Office • Development of open source tool kits to support governments in making use of Big EO Data analytics https://github.com/opendatacube

  6. Using the DEA/ODC API • Published • Surface water dynamics - Mueller et al. 2016 • Intertidal zone extent - Sagar et al. 2017 • Suspended sediment - Lymburner et al. 2017 • Coming soon • Wetlands in northern Australia • Mangrove extent and canopy density • Tidal composites • Coastal change • Automated change detection

  7. Perspectives from DEA for global ARD • Geometric accuracy • Per scene geometric accuracy accesible via API • Projection – Albers Equal Area • Radiometric accuracy • Collating historic in-situ measurements • Acquiring new in-situ measures • Working closely with the USGS ECCOE and LPCS • Pixel Quality Flags • Cloud • Cloud shadow • Per band saturation

  8. All you wanted to know about PQ… WITH SPECIAL THANKS TO STEFAN ERNST FROM HUMBOLDT UNIVERSITY (PATRICK HOSTERT’S LAB)

  9. PQ accessible via API, build your own mask – but has a default setting. • mask_components = { • 'cloud_acca' : 'no_cloud', • 'cloud_shadow_acca' : 'no_cloud_shadow', • 'cloud_shadow_fmask' : 'no_cloud_shadow', • 'cloud_fmask' : 'no_cloud', • 'blue_saturated' : False, • 'green_saturated' : False, • 'red_saturated' : False, • 'nir_saturated' : False, • 'swir1_saturated' : False, • 'swir2_saturated' : False, • 'contiguous' : True}

  10. Why bother configuring? Surely the cloud screening algorithms are perfect… • Take 30 years of observations • Count the number of times a particular PQ flag was tripped • If there’s no systematic errors of commission (surface targets flagged as cloud/cloud shadow) then this should simply reflect the distribution of cloud over 30 years…

  11. …and this is where it gets weird

  12. Persistent cloud shadow

  13. What on Earth…

  14. Per band saturation

  15. Proposed global ARD specification • 3 PQ flag layers • L1 Fmask • L2 Fmask • Atcor specific PQ information • LEDAPS • LaSRC • Errors of commission? • Recommendations/guidelines/API’s to enable automated processing?

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