https://w3id.org/sciencelive/np/RAGe9U1qrzbrHI6bZjkM7d3vuwbAkv5j1K0S5cEC8HYkk
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sub:assertion {
sub:turbidity-strong-limb-open-source-westerschelde a <https://w3id.org/sciencelive/o/terms/FORRT-Replication-Outcome>;
<http://schema.org/endDate> "2026-07-25"^^xsd:date;
<http://www.w3.org/2000/01/rdf-schema#label> "Open-source Sentinel-2 turbidity retrieval in the Westerschelde confirms the Sado strong-turbidity finding";
<https://w3id.org/sciencelive/o/terms/hasConclusionDescription> """This replication confirms the original claim. Sent et al. (2021) found that
Sentinel-2 MSI retrieves water-quality parameters with parameter-dependent
accuracy — strong for turbidity, weak for chlorophyll-a — and selected a
C2RCC + Nechad (cN783) chain that retrieved turbidity in strong agreement with in
situ (R² = 0.84). Testing that turbidity limb in an independent, more turbid
estuary (the Westerschelde, 2016–2026) with a fully open-source
atmospheric-correction chain (Acolite + Nechad et al. 2010, the aN783 chain), we
obtained strong agreement with in situ turbidity: R² = 0.92 with a near-unity
slope (0.86), meeting and slightly exceeding the paper's proprietary result. This
is the strong side of the parameter asymmetry the paper describes, and it
replicates even open-source: an operationally reproducible chain that uses no
proprietary processor recovers estuarine turbidity at, and slightly beyond, the
accuracy of the paper's selected cN783 chain, in a different optical regime.""";
<https://w3id.org/sciencelive/o/terms/hasConfidenceLevel> <https://w3id.org/sciencelive/o/terms/HighConfidence>;
<https://w3id.org/sciencelive/o/terms/hasEvidenceDescription> """From results/turbidity_satellite_acolite.parquet, agreement computed in linear
space (scripts/matchup_stats.py), matching the paper's linear treatment of
turbidity (turbidity is reported in FNU on both sides — no unit conversion):
N = 11 match-ups
R² = 0.92 (ours, aN783) vs R² = 0.84 (original, selected cN783)
slope = 0.86 (near unity)
RMSE = 10.13 FNU
BIAS = +6.91 FNU (slight overestimate)
The open-source Acolite + Nechad (aN783) chain therefore meets and slightly
exceeds the original study's selected C2RCC + Nechad (cN783) R² of 0.84, with a
near-unity regression slope, in a different and more turbid estuary. The small
positive bias (+6.91 FNU) indicates a mild systematic overestimate but does not
degrade the correlation. Turbidity is the strong side of the parameter asymmetry
seen across the three retrieved parameters. Match-up figure: figures/asymmetry.png.""";
<https://w3id.org/sciencelive/o/terms/hasLimitationsDescription> """Four factors bound this conclusion.
1. Sample size. N = 11 turbidity match-ups is small — fewer valid pairs than the
Chl-a limb (N = 33), and comparable to the original (N = 19–21). The R² = 0.92
therefore carries a wide confidence interval. The direction of the result
(strong agreement, meeting/exceeding the original) is robust; its precise
magnitude is not.
2. Processor rating. The paper reports Acolite as its worst-performing
atmospheric-correction processor, yet here the open-source Acolite + Nechad
chain matches and slightly exceeds the paper's selected C2RCC + Nechad result.
That is a notable finding, but a single-site one — it should not be read as a
general claim that Acolite outperforms C2RCC for turbidity everywhere.
3. Site and period change. This is a Replication, not a Reproduction: the Sado in
situ data are not public (paper Data Availability Statement), so we validated in
the Westerschelde (2016–2026), a different and more turbid mesotidal estuary.
A different optical regime tests generalisability, not the correctness of the
original analysis. Agreement was computed in linear space, matching the paper's
treatment of turbidity.
4. Systematic bias. The retrieval carries a slight positive bias (+6.91 FNU), a
mild overestimate that does not degrade the correlation but should be noted for
any quantitative use.
A grid-sensitivity check on a HEALPix / DGGS (GRID4EARTH) representation of the
corrected fields is deliberately out of scope here and deferred to a separate
follow-up chain that will extend this one, so the primary validation stays on the
native Sentinel-2 grid.""";
<https://w3id.org/sciencelive/o/terms/hasOutcomeRepository> <https://doi.org/10.5281/zenodo.21561994>;
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<https://orcid.org/0000-0002-1784-2920> <http://xmlns.com/foaf/0.1/name> "Anne Fouilloux" .
this: dc:created "2026-07-25T16:48:15.385Z"^^xsd:dateTime;
dc:creator <https://orcid.org/0000-0002-1784-2920>;
dc:license <https://creativecommons.org/licenses/by/4.0/>;
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<http://www.w3.org/2000/01/rdf-schema#label> "Open-source Sentinel-2 turbidity retrieval in the Westerschelde confirms the Sado strong-turbidity finding";
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