On Tuesday 26 May 2020, nd...@redhazel.co.uk wrote: > > Rasterization is a data generalization technique too.
No it isn't. Generalization is the most frequently abused term in cartography. Calling ST_Simplify and way_area filtering on OSM landcover polygon data generalization is a bit like calling JPEG compression noise reduction. But we are drifting off topic here. > Yes, in some > cases it leaves no artifacts at all Who would say that? In fact sampling artefacts (a.k.a. aliasing) are the mother of all artefacts in computer graphics. The point is that sampling artefacts are very well understood and it is known how to minimize them. > I've been looking into the code and I couldn't find anything related > to polygon generalization. Where is it done? Lossy geometry compression is happening in ST_AsMVTGeom - which is not just the inevitable coordinate rounding to the vector tile coordinate grid but also the subjective choice of per feature Douglas-Peucker line compression. See https://github.com/postgis/postgis/pull/463 for the well argued suggestion not to do that. The way_area filtering is explicit in the SQL code. -- Christoph Hormann http://www.imagico.de/ _______________________________________________ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
