@prefix this: <https://w3id.org/sciencelive/np/RAs--Uf0wMFAWeTv54c4P37QYNp70c8nxUY9M6HgOfg4c> .
@prefix sub: <https://w3id.org/sciencelive/np/RAs--Uf0wMFAWeTv54c4P37QYNp70c8nxUY9M6HgOfg4c/> .
@prefix np: <http://www.nanopub.org/nschema#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix prov: <http://www.w3.org/ns/prov#> .
@prefix npx: <http://purl.org/nanopub/x/> .
@prefix dc: <http://purl.org/dc/terms/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

sub:Head {
  this: a np:Nanopublication;
    np:hasAssertion sub:assertion;
    np:hasProvenance sub:provenance;
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sub:assertion {
  sub:wgs84-vs-sphere-sst-outcome a <https://w3id.org/sciencelive/o/terms/FORRT-Replication-Outcome>;
    <http://schema.org/endDate> "2026-04-22"^^xsd:date;
    <http://www.w3.org/2000/01/rdf-schema#label> "WGS84 ellipsoid HEALPix geometry reduces FOSCAT SST gap-filling RMSE by 167.7 mK (12.6%) over sphere at operational resolution               (nside=128)";
    <https://w3id.org/sciencelive/o/terms/hasConclusionDescription> "The PCC research question is answered affirmatively at operational resolution: using WGS84 ellipsoid geometry instead of perfect-sphere HEALPix when resampling lat/lon SST observations to HEALPix cells reduces FOSCAT scattering-transform gap-filling RMSE by 167.7 mK (12.6%)  at nside=128, on a single day of Copernicus Marine data. The geometry choice has a quantifiable effect on accuracy at the resolutions  actually used in operational SST analysis pipelines, where 0.25° native data is binned into HEALPix cells comparable in size to the  underlying observations. The benefit is resolution-dependent: at coarser resolution (nside=32), prior testing showed the WGS84 vs sphere  difference collapses to ~1.5 mK (0.14%), well within run-to-run variability — i.e. at coarse resolution the geometry choice doesn't  matter. The practical recommendation is to migrate to WGS84 geometry for operational SST gap-filling pipelines.";
    <https://w3id.org/sciencelive/o/terms/hasConfidenceLevel> <https://w3id.org/sciencelive/o/terms/Moderate>;
    <https://w3id.org/sciencelive/o/terms/hasEvidenceDescription> """Single-day comparison on Copernicus Marine SST for 2026-04-01 at HEALPix nside=128 (12 × 128² = 196,608 total pixels). Inputs: L3S PMW (cmems_obs-sst_glo_phy_l3s_pmw_P1D-m) with cloud gaps, L4 analysis (cmems_obs-sst_glo_phy-temp_nrt_P1D-m) as gap-free reference. Pipeline parameters: NORIENT=4, KERNELSZ=3, lmax=60 (harmonic baseline), 300 L-BFGS iterations, CPU. RMSE measured against L4 in cloudy ocean pixels  only.
Sphere geometry: 134,587 ocean / 69,547 observed / 65,040 gap pixels — RMSE = 1333.0 mK, runtime 2081.8 s.\\n\\nWGS84  geometry: 134,472 ocean / 69,626 observed / 64,846 gap pixels — RMSE = 1165.3 mK, runtime 2083.2 s.
Difference: WGS84 lower by 167.7  mK (12.6% relative reduction), with similar gap-pixel counts and identical runtime so the comparison is balanced. Full results JSON archived at Zenodo 10.5281/zenodo.19693573.""";
    <https://w3id.org/sciencelive/o/terms/hasLimitationsDescription> "Three caveats limit the strength of the conclusion. (1) Single-date evaluation. Only one day (2026-04-01) of L3S/L4 SST was tested at nside=128; cloud distribution, ocean regimes, and the gap pattern vary across days and seasons, so a multi-day study would strengthen the result. (2) L4 as ground truth. The 1333.0 / 1165.3 mK numbers are computed against the L4 operational analysis, not against in-situ measurements; L4 itself is an interpolation that may have its own systematic biases. (3) Single comparison resolution. This study's canonical run is at nside=128 only. The complementary nside=32 result (sphere 1061.6 mK, WGS84 1060.1 mK, 0.14% difference) is documented in the project's planning notes but is not part of this canonical archive — a future study should systematically scan resolution to map exactly how the WGS84 advantage scales.";
    <https://w3id.org/sciencelive/o/terms/hasOutcomeRepository> <https://doi.org/10.5281/zenodo.19707890>;
    <https://w3id.org/sciencelive/o/terms/hasValidationStatus> <https://w3id.org/sciencelive/o/terms/Validated>;
    <https://w3id.org/sciencelive/o/terms/isOutcomeOf> <https://w3id.org/sciencelive/np/RA0vq7OGc7G5we208CYmsu_3De-9IY0BN0yCLcXYBGBFA/wgs84-vs-sphere-sst-study> .
}

sub:provenance {
  sub:assertion prov:wasAttributedTo <https://orcid.org/0000-0002-1784-2920> .
}

sub:pubinfo {
  <https://orcid.org/0000-0002-1784-2920> <http://xmlns.com/foaf/0.1/name> "Anne Fouilloux" .
  
  this: dc:created "2026-04-26T19:00:25.366Z"^^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> "NP created using Declaring a replication study outcome according to FORRT";
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