change tutorial

Classify every unit between two versions of a polygon layer (unchanged, renamed, modified, relocated, split, merge, complex, created, removed) and get a changelog plus a colored spatial overlay for review.

Compare two versions¶

topo-tools change old.gpkg new.gpkg changelog.csv --overlay-file overlay.gpkg

Open overlay.gpkg alongside changelog.csv to review each classified unit on a map.

Link by a shared code¶

By default, units are linked by spatial overlap alone. If both versions share a stable unique code, link by it too for more reliable matching on heavily redrawn boundaries:

topo-tools change old.gpkg new.gpkg --link-by-code \
  --code-column-a adm2_pcode --code-column-b adm2_pcode

Loosen the overlap threshold¶

If legitimate boundary redraws are being misclassified as split/merge instead of modified, loosen the "related" overlap threshold:

topo-tools change old.gpkg new.gpkg --tau-match 0.6

See the change reference for the full classification rules.