DOC: note on a precision issue in enclosed_tessellation

[martinfleis]

We have noticed a nasty issue with the contiguity of enclosed tessellation caused by floating point imprecision within GEOS. Spent some time trying to fix it but I don't think it is possible with the current version of GEOS / shapely. For our use case, there is a solution, so making a note in the docstring.

Repr of the issue:

import geopandas as gpd
import momepy

streets = gpd.read_file(momepy.datasets.get_path("bubenec"), layer="streets")
buildings = gpd.read_file(momepy.datasets.get_path("bubenec"), layer="buildings")

enclosures = momepy.enclosures(streets, limit=momepy.buffered_limit(buildings, buffer=50))

tess = momepy.enclosed_tessellation(buildings, enclosures)

tess.union_all()

The lines shown in the interior are actual gaps in contiguity when building the graph:

from libpysal.graph import Graph

m = tess_new.explore()
g = Graph.build_contiguity(tess_new, rook=False, strict=True)
g.explore(tess_new, m=m)
m

It's been in the enclosed tessellation since the first implementation 4 years ago.

[codecov[bot]]

Codecov Report

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[martinfleis]

Just for a reference, this is how it should ideally look like.

[jGaboardi]

Is this something we are going to report upstream to shapely?

[martinfleis]

Is this something we are going to report upstream to shapely?

It is on my to-do list but I've been a bit demoralised by this finding so haven't managed to find a strength to come up with a minimal repr.

[martinfleis]

It's apparently expected... https://github.com/libgeos/geos/issues/1109