I'm looking for an algorithm for simplifying isochrones which were generated using OSM data.
These are generally characterised as having lots of small "holes" mostly due to missing OSM data but also frequently having small "islands" due to the use of transport like subways. I have tried a number of tools for this but all are too aggressive at shrinking space - most critically, deleting the islands. Reachability to these public transport islands is very important.
So rather than focusing on tools, I wanted to step back a bit and ask if any particular algorithms are well or not well suited to such a task? i.e. being aggressive at removing holes but conservative about not removing islands.
The isochrones start life in GeoJSON format. They eventually will be imported to PostGIS.