Nanopublication

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https://w3id.org/sciencelive/np/RAW7XIpK-5SmVOoRoVPl-w_xjr9cqgM8xRRIKQ575RVXs
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@prefix this: <https://w3id.org/sciencelive/np/RAW7XIpK-5SmVOoRoVPl-w_xjr9cqgM8xRRIKQ575RVXs> .
@prefix sub: <https://w3id.org/sciencelive/np/RAW7XIpK-5SmVOoRoVPl-w_xjr9cqgM8xRRIKQ575RVXs/> .
@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;
    np:hasPublicationInfo sub:pubinfo .
}

sub:assertion {
  sub:s2-equal-area-healpix-outcome a <https://w3id.org/sciencelive/o/terms/FORRT-Replication-Outcome>;
    <http://schema.org/endDate> "2026-06-27"^^xsd:date;
    <http://www.w3.org/2000/01/rdf-schema#label> "Sentinel-2 equal-area HEALPix power-spectrum outcome";
    <https://w3id.org/sciencelive/o/terms/hasConclusionDescription> """The angular power spectrum of a Sentinel-2 scene can be computed end to end on an equal-area HEALPix grid on the WGS84 ellipsoid with the GRID4EARTH stack
(healpix-geo + healpix-analyse). Because every HEALPix cell covers the same surface area, the resulting spectrum carries none of the latitude-dependent area
weighting that a lon/lat grid would impose — supporting the claim by construction. The spectrum shows the expected monotonic power-law fall-off with
spatial frequency, the signature of a natural surface-reflectance field.""";
    <https://w3id.org/sciencelive/o/terms/hasConfidenceLevel> <https://w3id.org/sciencelive/o/terms/Moderate>;
    <https://w3id.org/sciencelive/o/terms/hasEvidenceDescription> """Configuration and result recorded in results/powerspectrum.json:
- scene S2A_22WEV_20190723, band B04 (red, 10 m), 256×256 px window (~2.6 km)
- equal-area HEALPix at depth 18 (nside = 262144), ellipsoid = WGS84
- field sampled at equal-area cell centres, then radially-averaged isotropic power spectrum computed with healpix-analyse `ps`
- the spectrum (results/powerspectrum.png) falls off monotonically with spatial frequency on a log–log axis (power-law behaviour), with no latitude-dependent amplitude term, because the cells are equal-area by construction.

Github repository: https://github.com/annefou/healpix-analyse-s2-powerspectrum""";
    <https://w3id.org/sciencelive/o/terms/hasLimitationsDescription> """The repo demonstrates the equal-area pipeline rather than quantifying the lon/lat bias it avoids: no side-by-side lon/lat baseline spectrum is computed here, so
the bias magnitude is argued by construction, not measured. Single scene, single band, single date; no atmospheric, cloud, or coastal effects; generalisation to other sensors and to a controlled multi-latitude comparison is left to follow-up.""";
    <https://w3id.org/sciencelive/o/terms/hasOutcomeRepository> <https://doi.org/10.5281/zenodo.21000097>;
    <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/RALm0wEYfKg4NKqTwY33LsGKIR7UH0Ut2IgYvX8uEeJMM/s2-equal-area-healpix-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 "2026-06-28T15:46:05.059Z"^^xsd:dateTime;
    dc:creator <https://orcid.org/0000-0002-1784-2920>;
    dc:license <https://creativecommons.org/licenses/by/4.0/>;
    npx:introduces sub:s2-equal-area-healpix-outcome;
    npx:wasCreatedAt <https://platform.sciencelive4all.org>;
    <http://www.w3.org/2000/01/rdf-schema#label> "Sentinel-2 equal-area HEALPix power-spectrum outcome";
    <https://w3id.org/np/o/ntemplate/wasCreatedFromTemplate> <https://w3id.org/np/RA2zljn0Nw9SadppOyxZoh-_Rxosslrq-vYG-p9SttnJE> .
  
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    npx:hasSignatureTarget this:;
    npx:signedBy <https://orcid.org/0000-0002-1784-2920> .
}