Polygon simplification with penalty for sharp corners

[wipfli]

When doing polygon simplification, I often get sharp corners when I increase the pixel tolerance. I personally find this looks bad.

Is there a method which gives a penalty for sharp corners when doing the polygon simplification?

I would be happy to trade off area accuracy for fewer sharp corners...

[wipfli]

Wang-Müller might be a good choice. Playing around at the moment with a QGIS plugin that implements it: https://github.com/NRCan/geo_sim_processing

[msbarry]

There's also visvalingham wyatt meant to smooth out edges. I believe natural earth uses visvalingham wyatt with effective area from https://mapshaper.org to generalize shapes at low zooms

[wipfli]

Love esri docs...

[msbarry]

Nice, those are good names that describe what they do too. In general I think planetiler should have flexible support for multiple kinds of simplification/smoothing with more flexible options, or maybe even pipelines that compose multiple operations like this in a row.

[wipfli]

Oh yeah a geometry pipeline could be fun!

[wipfli]

For polygonized raster data an easy way could also be to do a bit of midpoint smoothing, see https://github.com/wipfli/midpoint-smoothing :

[brawer]

IGN, the French National Institute of Geographic and Forest Information, implemented various cartographic algorithms in Java. See their web page and code repository. They appear to have switched to Python, see here, but the Java code might still be interesting to read.