ACIX and CMIX intro

ACIX and CMIX

The Atmospheric Correction Intercomparison eXercise (ACIX) and the Cloud Masking Intercomparison eXercise (CMIX) are international collaborative initiatives jointly organized by ESA and NASA within the frame of CEOS WGCV to inter-compare a set of atmospheric correction (AC) and cloud masking (CM) algorithms for high-spatial resolution optical sensors.

The ACIX and CMIX exercises, initiated in 2016, are conducted through successive editions designed to periodically re-assess the performance, consistency, and agreement of the latest generation of processors and models in the optical EO domain. By bringing together a wide range of methodologies and datasets, these exercises foster model improvements and support continued advancements across the respective modelling communities. A central objective is to identify strengths and weaknesses in current approaches, while also highlighting key commonalities and differences in model behaviour, thereby contributing to the development of more robust, reliable, and harmonised EO products.

  • Intercomparison Exercise Workflow

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  • Over 9 years of activities, with ACIX (2016 – 2018) and ACIX-II Land/Aqua (2018 – 2021) using Landsat and Sentinel-2 imagery, ACIX-III Land and Aqua (2021 – 2025) using hyperspectral imagery, and ACIX-IV Land and Aqua currently in preparation, which will rely on synthetic scenes, as well as on real multi- and hyperspectral images.
  • Dedicated activities for scenes over land and those over water from the second implementation
      
  • Initially introduced in ACIX (2016–2018), cloud masking became a dedicated CMIX activity (2018–2021) using Landsat and Sentinel‑2 data and has been further expanded in CMIX‑II (2021–ongoing) with additional ground reference datasets.
  • Both physical and machine‑learning approaches are considered, ensuring a broad and balanced intercomparison framework.

 

Contact

If you have questions or feedback on ACIX and CMIX initiative, please contact:

Michela Perrone | Serco c/o European Space Agency, ESA/ESRIN  | michela.perrone@ext.esa.int

Ferran Gascon | European Space Agency, ESA/ESRIN  | ferran.gascon@esa.int

If you have questions or feedback on the webpages of ACIX and CMIX, please contact:

Paolo Castracane | Starion Group c/o European Space Agency, ESA/ESRIN | paolo.castracane@ext.esa.int