jiayuasu commented on code in PR #2529:
URL: https://github.com/apache/sedona/pull/2529#discussion_r3612360528
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python/sedona/spark/geopandas/base.py:
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@@ -712,19 +712,25 @@ def centroid(self):
return _delegate_to_geometry_column("centroid", self)
def concave_hull(self, ratio=0.0, allow_holes=False):
- """Return the concave hull of each geometry.
+ """Return a ``GeoSeries`` of geometries representing the concave hull
+ of vertices of each geometry.
- The concave hull of a geometry is a possibly concave geometry that
- encloses the input geometry.
+ A concave hull is a concave or convex `Polygon` containing all the
+ vertices in each geometry. For two vertices, the hull collapses to a
+ `LineString`; for one vertex, it collapses to a `Point`.
+
+ The hull is constructed by removing border triangles of the Delaunay
+ triangulation while their size is larger than the maximum edge length
+ ratio. The ratio is a fraction of the difference between the longest
+ and shortest edges in the triangulation.
Review Comment:
Reworded this in fef658e1da3 to state that ratio determines the maximum
edge-length threshold by interpolating between the shortest and longest
Delaunay edges. This keeps the documented JTS semantics while removing the
ambiguous comparison between triangle size and a dimensionless ratio.
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