Administrative boundary changes

temporal

Municipal annexations, incorporations, and county line adjustments change which admin polygon a location belongs to over time; a crosswalk built on one vintage misattributes cells for periods before or after the change.

Detection

Compare admin polygon vintages across the reporting period; flag any cell whose admin assignment differs between the vintage in effect at event time and the vintage used for the join.

Mitigation

Version every admin boundary crosswalk with validFrom/validTo dates
Join each event to the boundary vintage in effect on the event's own date, not the current vintage

Affected conversions

Admin polygons → H3 (max-overlap partition) approximate
Admin polygons → H3 (weighted crosswalk) weighted