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edge-extend

Inputs

  • edge-extend MUST read the input and reproject it to EPSG:4326.
  • If the reprojected input has any coverage violation (an overlap or a mismatched shared edge), edge-extend MUST correct it before continuing; otherwise it MUST leave the input unmodified.
  • Correcting a violation MAY shift any polygon's boundary, not just the violating one.
  • edge-extend MUST NOT distinguish a real hole from a digitization gap; both are left for the boundary-extension stage.

Extracting boundaries

  • Each polygon's exterior boundary MUST be its own boundary minus the combined boundary of every bounding-box-overlapping neighbor. A polygon with no such neighbor MUST keep its full boundary.

Generating the boundary extension (points and Voronoi cells, retried together)

  • edge-extend MUST generate points along each polygon's exterior boundary, at a target spacing, as input to a Voronoi diagram.
  • The target spacing MUST default to the smaller of a fixed default or the file's own median real segment length.
  • A single real segment MUST NOT contribute more than a fixed cap's worth of points.
  • Generated points MUST exclude a buffered zone around every shared boundary endpoint.
  • edge-extend MUST build a Voronoi diagram from the points, assign each cell to the polygon whose point generated it, and union cells by polygon into that polygon's extension.
  • On failure, or more points than a fixed maximum, edge-extend MUST retry with the spacing doubled from the resolved default, up to 10 times, then raise.

Merging

  • Each polygon's final geometry MUST be its original geometry combined with the portion of its own extension not already covered by a nearby original polygon.
  • edge-extend MUST snap an extension to its nearby original neighbors, using a small fixed tolerance, before subtracting them.
  • edge-extend MUST run one whole-layer coverage-clean pass afterward, using a gap-closing width equal to the snapping tolerance, not a shape-based heuristic.

Outputs

  • edge-extend's final output MUST pass the coverage check (no overlap, no gap) before export.
  • edge-extend MUST export the final merged layer.

Configuration (api.edge_extend.extend() / CLI)

  • edge-extend MUST process exactly one input file per call.
  • The output path MUST default to the input path with an _extended suffix.
  • edge-extend MUST raise FileExistsError if the output exists and overwriting wasn't requested.
  • step, if given, MUST be one of inputs, lines, attempt, merge, outputs; any other value MUST raise ValueError.

Examples

Example 1: basic run, output name chosen automatically

topo-tools edge-extend example.geojson

Example 2: explicit output

topo-tools edge-extend example.gpkg example_extended.gpkg

Example 3: rerun and overwrite a previous output

topo-tools edge-extend example.parquet example_extended.parquet --overwrite