Incorrect ring winding order

geometry

GeoJSON requires exterior rings counter-clockwise and holes clockwise (right-hand rule); reversed winding flips interior/exterior for winding-sensitive fillers.

Detection

Compute signed area (shoelace formula); sign mismatch against RFC 7946 convention for the ring role.

Mitigation

Normalize winding on ingest (rewind exterior CCW, holes CW)
Validate with a strict GeoJSON linter before filling

Affected conversions

Polygon → H3 (center-contained) approximate
Polygon → H3 (fully-contained) conservative
Polygon → H3 (intersects) expansive