Fix gaps and overlaps in one layer

Detect coverage defects (gaps, overlaps) in a single polygon layer, then fix them.

Inspect first, without fixing anything:

topo-tools topo-detect admin2.geojson

This writes admin2_issues.geojson, listing every gap/overlap with its area, width, and (for gaps) a compactness score. Review it to judge which gaps are real features (a strait, a lake) versus digitization slivers, before picking a fix width.

Fix gaps at or below the default snap tolerance, plus every overlap:

topo-tools topo-clean admin2.geojson admin2_cleaned.geojson \
  --issues-file admin2_cleaned_issues.geojson

Widen the fill to every thin, elongated gap regardless of size (--maximum-gap-width thin), or every detected gap regardless of shape (--maximum-gap-width all), or a specific decimal-degree width. The issues file records each defect's actual fixed outcome, not just what was detected.

See topo-detect reference, topo-clean reference, and their explanation pages for the full gap/overlap detection and fix rules.