Bug-fix release to address issue with GFM observed flood extent and likelihood values

In recent weeks, the GFM algorithm development team has investigated some inconsistent flood classification likelihood values that were spotted for certain Sentinel-1 scenes.

It was discovered that one of the three individual algorithms that are deployed in parallel by the GFM ensemble flood mapping flood algorithm, produced inaccurate likelihood values in cases where the geographic extent of the reference and near real-time images scenes used by that algorithm, differed. This in turn resulted in overestimated likelihood values produced by the GFM ensemble algorithm, in cases where either the reference or near real-time image scene is not available.

An additional issue with one of the individual flood mapping algorithms, related to the reading of an auxiliary dataset, was identified during routine code checks by the algorithm teams. As a result, since 24 January 2024 that particular algorithm was not contributing to the Observed Flood Extent results produced by the GFM ensemble flood mapping.

The root causes of both issues have now been identified, and a fixed version of the GFM ensemble flood mapping algorithm has been deployed on 4 April  2024, following quality checks. As a result of the above issues, the planned release of the entire GFM re-processed Sentinel-1 data archive, has been delayed.

The bug-fix release is documented in the GFM Versioning.