Interactive publication
Back to the catalogueGlobalCase 09 of 12
Offshore islands
Small islands belonging to a mainland admin region are geometrically disjoint (multipolygon parts) and can be dropped by fillers that assume a single contiguous ring.
Class
Case to account for
Affects
3 conversions
01
Detection
MultiPolygon feature where one or more parts have a centroid far outside the bounding box of the largest part.
02
Mitigation
01
Iterate all multipolygon parts explicitly, never just the largest
02
Verify per-part cell coverage in QA rather than aggregate area only
03
Affected conversions
PolygonH3 (intersects)
OPENAdmin polygonsH3 (max-overlap partition)
OPENAdmin polygonsH3 (weighted crosswalk)
OPEN