On Monday 16 April 2018, Martin Koppenhoefer wrote: > AFAIK, in the osm-carto style there is no generalization on live data > for performance reasons (because of continuous data updates via > minutely diffs). There are some precomputed / extracted data files > though, some of which contain generalized (simplified) data. These > are all "external" sources:
I think this requires some clarification. There are different definitions of what kind of operations and processes you call "generalization". But typically selection is considered a generalization operation meaning that most of what is shown at all but the highest zoom levels is shown with some level of generalization. Most selection is rather primitive - based on fixed zoom level thresholds, the dreaded way_area filtering etc. There are very limited attempts at some additional sophistication, like for populated place rendering at low to mid zoom levels. When talking about explicit geometric generalization while specifically exclusing lossy vector data compression (which is widely mischaracterized as generalization) the Natural Earth boundaries at z=1-3 is currently the only case. Lossy vector data compression in addition is currently/historically used in the following places: * Coastlines at z8-9 - the visual impact of this was rather small but visible in some areas (in particular with small islands) if you kept an eye on it at the transit from z9 to z10. This has been the case for a long time but is essentially superseded by: * Coastlines at z0-9 since https://github.com/gravitystorm/openstreetmap-carto/pull/3065 * The administrative boundaries at z4+ since https://github.com/gravitystorm/openstreetmap-carto/pull/3103 You need to keep in mind that both geometric generalization and lossy vector data compression operations are largely incompatible with the current goals of OSM-Carto: https://github.com/gravitystorm/openstreetmap-carto/blob/master/CARTOGRAPHY.md -- Christoph Hormann http://www.imagico.de/ _______________________________________________ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
