@prefix this: . @prefix sub: . @prefix np: . @prefix rdf: . @prefix prov: . @prefix npx: . @prefix dc: . @prefix xsd: . sub:Head { this: a np:Nanopublication; np:hasAssertion sub:assertion; np:hasProvenance sub:provenance; np:hasPublicationInfo sub:pubinfo . } sub:assertion { sub:sentinel2-parameter-asymmetry-open-source-westerschelde a ; dc:subject , , , , , ; , ; "2026-07-25"^^xsd:date; "Open-source Sentinel-2 reproduces the parameter-dependent water-quality retrieval asymmetry in the Westerschelde"; """This synthesis holds within the following scope: - Domain and site: a turbid, mesotidal, well-mixed temperate estuary — the Westerschelde (Netherlands). It generalises to comparable optically complex Case-2 estuaries, not to clear open-ocean (Case-1) water. - Processing chain: the fully open-source Acolite atmospheric correction with the Gons et al. (2005) red-edge algorithm for chlorophyll-a (aGS) and the Nechad et al. (2010) algorithm for turbidity (aN783). This is NOT the paper's proprietary C2RCC chain (cGS / cN783); the synthesis compares an open-source chain against the paper's proprietary result and does not re-run C2RCC. - Sensor and period: Sentinel-2 MSI (A/B/C era), imagery 2016–2026. - Reference: coincident Rijkswaterstaat in situ observations at along-axis stations; turbidity compared in linear space (FNU on both sides, no unit conversion), chlorophyll-a compared in log10 space, matching the paper's treatment of each. - Sample sizes: small — turbidity N = 11 match-ups, chlorophyll-a N = 33. The direction of each verdict is robust; precise magnitudes carry wide uncertainty. - Design: a Replication (different site, different period, open-source processor), not a Reproduction — the Sado in situ data are not public. - Out of scope: grid-sensitivity of the retrieval (a HEALPix / DGGS GRID4EARTH representation of the corrected fields) is deferred to a separate follow-up chain that will extend this one; the primary validation stays on the native Sentinel-2 grid."""; """1. Not a head-to-head processor test. The paper's headline numbers (cGS R² = 0.63, cN783 R² = 0.84) are the proprietary C2RCC chain, which was never run here (C2RCC exists only inside ESA SNAP and crashes in the container). The synthesis compares an open-source chain against the paper's published proprietary result; it does not prove the open-source chain equals C2RCC on the same imagery. In particular, the finding that open-source Acolite matches C2RCC for turbidity is a single-site observation, not a general claim that Acolite outperforms C2RCC everywhere. 2. Small samples. With N = 11 (turbidity) and N = 33 (chlorophyll-a), each R² carries a wide confidence interval. The composed asymmetry is qualitatively robust across the two limbs; the exact R² values should not be over-read. 3. Single estuary, single reference network. Both limbs were validated in one Westerschelde record against one in situ provider. Whether the parameter-dependent asymmetry holds in structurally different estuaries, or against other reference networks, was not tested here. 4. Retrieval bias not corrected. The turbidity retrieval carries a slight positive bias (+6.91 FNU) and the chlorophyll-a retrieval a positive bias with a negative slope; these are reported, not corrected, and would matter for any quantitative use. 5. Grid representation untested. Any sensitivity of these verdicts to spatial re-gridding (HEALPix / DGGS) is explicitly out of scope and deferred to a follow-up chain."""; """1. Do not treat \"Sentinel-2 water-quality retrieval\" as a single capability. Validate and report accuracy per parameter: a chain trustworthy for turbidity can be simultaneously unreliable for chlorophyll-a in the same water. 2. For estuarine turbidity monitoring (e.g. Water Framework Directive reporting), a fully open-source Acolite + Nechad chain is a viable, citable alternative to the proprietary C2RCC processor — here it matched and slightly exceeded the proprietary result in a different estuary. 3. For estuarine chlorophyll-a, treat MSI retrievals in turbid Case-2 water as provisional. The paper's call for \"a more complete set of match-ups\" stands; collect more coincident in situ pairs and validate locally before any operational use, and do not assume a red-edge algorithm is tracking pigment rather than backscatter. 4. Prefer open-source, operationally reproducible processing chains for replication and monitoring: they make the retrieval auditable end-to-end and, on the turbidity limb here, cost nothing in accuracy."""; """Sent et al. (2021) reported that Sentinel-2 MSI retrieves estuarine water-quality parameters with parameter-dependent accuracy — strong for turbidity, weak for chlorophyll-a. This synthesis composes two independent replication limbs and finds that the asymmetry itself is what replicates. In an independent, more turbid estuary (the Westerschelde) and with a fully open-source atmospheric-correction chain (Acolite), the two parameters behave exactly as the paper's asymmetry predicts, but they land on opposite verdicts. The turbidity limb CONFIRMS the paper: the open-source Acolite + Nechad (aN783) chain retrieves in situ turbidity in strong agreement, R² = 0.92 with a near-unity slope (0.86), meeting and slightly exceeding the paper's proprietary C2RCC + Nechad (cN783) result of R² = 0.84. The chlorophyll-a limb QUALIFIES the paper's own caution: the open-source Acolite + Gons (aGS) chain achieves no useful agreement with in situ chlorophyll-a, R² = 0.10 (log10 space), far below the paper's selected C2RCC + Gons (cGS) result of R² = 0.63, deepening rather than resolving the weakness the original authors flagged. The composed, replicated result is therefore not a single accuracy number but a structural property: Sentinel-2 water-quality retrieval accuracy is parameter-dependent, and that dependence survives both a change of estuary and the replacement of the proprietary processor by an open-source one.""" . } sub:provenance { sub:assertion prov:wasAttributedTo . } sub:pubinfo { "Anne Fouilloux" . this: dc:created "2026-07-25T16:49:06.935Z"^^xsd:dateTime; dc:creator ; dc:license ; npx:introduces sub:sentinel2-parameter-asymmetry-open-source-westerschelde; npx:wasCreatedAt ; "Open-source Sentinel-2 reproduces the parameter-dependent water-quality retrieval asymmetry in the Westerschelde"; . sub:sig npx:hasAlgorithm "RSA"; npx:hasPublicKey "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"; npx:hasSignature "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"; npx:hasSignatureTarget this:; npx:signedBy . }