https://w3id.org/sciencelive/np/RANLZSWPo1AXNszhQDilv20UB6wM32Gp6WzbUhTCfzUK4
.trig | .trig.txt | .jelly | .jelly.txt | .jsonld | .jsonld.txt | .nq | .nq.txt | .xml | .xml.txt
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sub:Head {
this: a np:Nanopublication;
np:hasAssertion sub:assertion;
np:hasProvenance sub:provenance;
np:hasPublicationInfo sub:pubinfo .
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sub:assertion {
sub:healpix-wgs84 a <https://w3id.org/sciencelive/o/terms/FORRT-Replication-Outcome>;
<http://schema.org/endDate> "2026-04-08";
<http://www.w3.org/2000/01/rdf-schema#label> "WGS84 Ellipsoid Significantly Affects HEALPix Cell Assignment at Mid and High Latitudes";
<https://w3id.org/sciencelive/o/terms/hasConclusionDescription> "WGS84 ellipsoid indexing assigns pixels to substantially different HEALPix cells than sphere-based indexing, particularly at mid and high latitudes. At mid-latitudes (+48°), 98% of pixels are assigned to a different cell. This demonstrates that sphere-based HEALPix indexing is unsuitable for European Earth observation data (Copernicus/Sentinel, 45-65°N). ";
<https://w3id.org/sciencelive/o/terms/hasConfidenceLevel> <https://w3id.org/sciencelive/o/terms/HighConfidence>;
<https://w3id.org/sciencelive/o/terms/hasEvidenceDescription> """ ELLIPSOID ANALYSIS (HEALPix depth 9, sphere vs WGS84):
| Region | Center lat | Pixels in different cell | Jaccard similarity |
|---------------|------------|--------------------------|-------------------|
| Equatorial | 0° | 26.6% | 0.9951 |
| Mid-latitude | +48° | 98.4% | 0.9844 |
| High-latitude | +62° | 90.8% | 0.9868 |
| Arctic | +78° | 52.6% | 0.9908 |
At mid-latitudes (Mediterranean, +48°), nearly every pixel (98.4%) is assigned to a different HEALPix cell when using sphere vs WGS84 ellipsoid.
Polygon coverage Jaccard similarity drops to 0.9844, indicating measurable differences in spatial coverage. The effect peaks at mid-latitudes
where the WGS84 ellipsoid deviates most from a sphere, and decreases towards the equator and poles. """;
<https://w3id.org/sciencelive/o/terms/hasLimitationsDescription> """ - Uses synthetic raster grids, not real Earth observation data
- Single HEALPix depth (9) tested -- effect may vary at other depths
- Four latitude bands only; continuous latitude sweep not performed
- Does not quantify downstream impact on scientific analyses (e.g., land cover classification accuracy) """;
<https://w3id.org/sciencelive/o/terms/hasOutcomeRepository> <https://doi.org/10.5281/zenodo.19488374>;
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<https://w3id.org/sciencelive/o/terms/isOutcomeOf> <https://w3id.org/sciencelive/np/RAocR3vJTYJPEfL8vIBN2cjEFie2vT-tvhOS7IA431Dqk/healpix-replication2> .
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sub:provenance {
sub:assertion prov:wasAttributedTo <https://orcid.org/0000-0002-1784-2920> .
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sub:pubinfo {
<https://orcid.org/0000-0002-1784-2920> <http://xmlns.com/foaf/0.1/name> " Anne Fouilloux" .
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dc:created "2026-04-09T20:59:47.543Z"^^xsd:dateTime;
dc:creator <https://orcid.org/0000-0002-1784-2920>;
dc:license <https://creativecommons.org/licenses/by/4.0/>;
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