pelias
Sharding invalid geometries
The 'shard' process halves a geometry (alternating horizontally & vertically) until each shard complexity is below a fixed threshold. This ensures that the PIP performance is fast and linear.
This process is tested and works well, however, I have seen some geometries which fail to split due to topology errors. It's pretty rare, it doesn't affect any WOF geometries and less than 1 in 10,000 OSM geometries.
I'll open up a separate issue related to repairing invalid geometries, but this issue is simply to handle the case where sharding fails due to a topology error.
In the case where a shard fails to half, we should:
- discard both of the two child halves (the ones created at
level+1) - do not delete the parent shard (the one at
level)
I attempted to fix this in the past but for some reason IsValid() is returning 1 despite the shard geom being invalid.
It might be that spatialite@5 is better at handling this because it uses LIBRTTOPO instead of GEOS.
