Why do we render place=island polygons in the default style?
Hi all, we came accross this in this discussion : http://gis.19327.n5.nabble.com/Option-to-output-polygons-in-size-order-tp587... The polygons file contains these two rules: place=island & name=* [0x53 resolution 19] place=islet & name=* [0x53 resolution 20] I assume they were added to "catch" small islands within lakes, but they are producing really large and complex polygons for islands like the monster mp-relation 6038068<https://www.openstreetmap.org/relation/> which covers the mainland of the UK. According to GPS MapEdit the polygon type 0x53 seems to stand for "Sandbank, tidal/mud flat", which might be good for very small islands/islets, but makes no sense for really large islands. What would be missing without the 1st rule, esp. when precompied sea data is also used? I can think of adding more clauses, e.g. place=island & name=* & natural!=coastline ... place=island & name=* & area_size() <= 100000 ... Any thoughts? Gerd
Hi Gerd, I guess there could exist instances, where sea/lake doesn't include a hole and island can be overlaid over water. But these are errors easy to correct in OSM data. Other function for these objects is to add a label to an area. In my styles I have removed islands from polygons but left them as a POI. From your suggestions I would prefer to limit islands by size, condition natural!=coastline probably won't work correctly for/because of relations. -- Best regards, Andrzej
Hi Andrzej sure, we want to have the POI, I don't want to touch the rules in points. Reg. coastline: My thinking is that we can ignore even small islands when they have the natural=coastline attribute, so something like place=island & name=* & area_size() < 1000000 & !(natural=coastline) [0x53 resolution 19] Gerd ________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej@poczta.onet.pl> Gesendet: Montag, 25. Juli 2016 15:22:26 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Why do we render place=island polygons in the default style? Hi Gerd, I guess there could exist instances, where sea/lake doesn't include a hole and island can be overlaid over water. But these are errors easy to correct in OSM data. Other function for these objects is to add a label to an area. In my styles I have removed islands from polygons but left them as a POI. From your suggestions I would prefer to limit islands by size, condition natural!=coastline probably won't work correctly for/because of relations. -- Best regards, Andrzej _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Hi Gerd, island is a relation (multipolygon) while natural=coastline is a tag from a line, not from relation. Would mkgmap find this tag when processing multipolygon? -- Best regards, Andrzej
Hi Andrzej, I am not sure what tags are copied in the mp code, but if the answer is "no" it will do no harm besides that the island is rendered, which always happens now. Gerd ________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej@poczta.onet.pl> Gesendet: Montag, 25. Juli 2016 18:49:21 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Why do we render place=island polygons in the default style? Hi Gerd, island is a relation (multipolygon) while natural=coastline is a tag from a line, not from relation. Would mkgmap find this tag when processing multipolygon? -- Best regards, Andrzej _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
Maybe it would be better to move the rule for place=island after the rules in include inc/landuse_polygons . Many polygons are tagged with place=island and landuse=* or natural=* and I think that is the more important info. Gerd ________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <GPetermann_muenchen@hotmail.com> Gesendet: Montag, 25. Juli 2016 19:37:28 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] Why do we render place=island polygons in the default style? Hi Andrzej, I am not sure what tags are copied in the mp code, but if the answer is "no" it will do no harm besides that the island is rendered, which always happens now. Gerd ________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej@poczta.onet.pl> Gesendet: Montag, 25. Juli 2016 18:49:21 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Why do we render place=island polygons in the default style? Hi Gerd, island is a relation (multipolygon) while natural=coastline is a tag from a line, not from relation. Would mkgmap find this tag when processing multipolygon? -- Best regards, Andrzej _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
participants (2)
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Andrzej Popowski -
Gerd Petermann