Re: [OSM-dev] Processing dual carriageway highways into one linestring?`
Joseph Eisenberg wrote:
> Is anyone aware of a way to import dual-carriageway roads as
> a single linestring?
I do something like this to boil route relations containing dual
carriageways down into polylines:
insert into routes_split(geom) (
select (st_dump(
st_linemerge(
st_approximatemedialaxis(
st_simplifypreservetopology(
st_multi(
st_buildarea(
st_buffer( st_collect(r.way) ,50 )
)
)
,20)
)
)
)
).geom from (select way from routes where osm_id in (#{ids})) r )
But it's not an all-purpose solution, just something that works at small
scales (where junctions are unlikely to be significant) and for route
reconstruction purposes. I doubt very much that this approach would work
with osm-carto's principle of no preprocessing.
Richard
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Re: [OSM-dev] Processing dual carriageway highways into one linestring?`
You would also have to know how many ways there are, just looking for 2 is not sufficient, because there could be 3, 4, 5, 6 or even more. Around here I've a situation with 6 parallel carriageways: https://www.openstreetmap.org/#map=19/41.86472/12.49702 some meters north of this spot, they are even 7 for a short length (or 8, if you count the cycleway and 9 if you also count the parking aisle). And you would have to decide when not to do it, for example Via Palos runs for some time parallely but then makes a turn and passes under the bridge: https://www.openstreetmap.org/way/257174994#map=17/41.86821/12.49583 And if there are ways that run along the "principal" highway for some time at only one side, but then vanish, and you calculate the center for the "synthesis", it will put corners or curves in your main way which actually runs straight. You will surely have to define a maximum distance threshold for this unification, and you always will have edge cases around this threshold which can cause inconsistency. Depending on your purpose, you also may want to not unify parallel ways when they run on different levels, e.g. one on a bridge or embankment (e.g. along a retaining wall), or in a cutting. As you probably know, the typical OSM solution for this is raster rendering, because then the ways merge visually and "automatically" (as their width is usually exagerated and layer ordering renders first the casing then the fill). Cheers Martin ___ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Processing dual carriageway highways into one linestring?`
Hi! On Fri, Oct 18, 2019 at 11:29:04AM +0900, Joseph Eisenberg wrote: > Is anyone aware of a way to import dual-carriageway roads as a single > linestring? > > There's a request at Openstreetmap-carto to render dual-carriageway > roads differently at mid-zoom levels: > https://github.com/gravitystorm/openstreetmap-carto/issues/3934 > > It doesn't appear that there are any tags in the database which hold > this information. Ideally one would import a linestring midway between > two highway ways, if they were tagged with the same highway class, > name, and oneway=yes, but it could be difficult to get this right at > locations where the two carriageways separate. > > Has anyone implemented a rendering that handles dual-carriageway > roads, or designed a way to import such ways into a (rendering) > database as a single linestring midway between the two OSM ways? I have experimented with this and never got far enough to make this actually useful. It is incredibly difficult to find the center line between two carriage ways. The problem is not the lines, but the junctions. All the algorithms I have tried do the right thing in many cases but totally jumble up some complex junctions. I think that with some more effort it should be possible to do this for some cases, like only showing motorways in low-zoom level maps. But aggregating the lines for mid to high zoom levels in urban areas is really hard, especially when you expect the generalized center lines to still connect to the rest of the road network. Jochen -- Jochen Topf joc...@remote.org https://www.jochentopf.com/ +49-351-31778688 ___ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Processing dual carriageway highways into one linestring?`
Hi Joseph, Am 18.10.19 um 04:29 schrieb Joseph Eisenberg: > Has anyone implemented a rendering that handles dual-carriageway > roads, or designed a way to import such ways into a (rendering) > database as a single linestring midway between the two OSM ways? We had a student at Geofabrik working on a programme to conflate multiple parallel line strings of roads and railways as part of his diploma thesis. Author: Arne Johanessen Title: Algorithmen zur automatisierten Generalisierung durch Zusammenfassung von Linienzügen in OpenStreetMap für konkrete Spezialfälle (translated title: Algorithms for automatic generalisation by conflation of linestrings in OpenStreetMap for specific special cases) Year: 2018 Full text PDF (German) is available at http://www.geofabrik.de/media/2018-03-02-johannessen-diplomarbeit-generalisierung.pdf The source code is available at https://github.com/johannessen/combiner The software is licensed under BSD 3-clause license. Best regards Michael -- Michael Reichert www.geofabrik.de Geofabrik GmbHHandelsregister: HRB Mannheim 703657 Amalienstr. 44Geschaeftsfuehrung: C. Karch, F. Ramm 76133 Karlsruhe Tel: 0721-1803560-3 reich...@geofabrik.de Fax: 0721-1803560-9 signature.asc Description: OpenPGP digital signature ___ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
Re: [OSM-dev] Processing dual carriageway highways into one linestring?`
18 Oct 2019, 04:29 by joseph.eisenb...@gmail.com: > Is anyone aware of a way to import dual-carriageway roads as a single > linestring? > I tried searching for way/tool that would do this some time ago and failed. > It doesn't appear that there are any tags in the database which hold > this information. > As I needed very accurate data I started to use dual_carriageway=yes in my city - and I remain the only person using this tag. ___ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
[OSM-dev] Processing dual carriageway highways into one linestring?`
Is anyone aware of a way to import dual-carriageway roads as a single linestring? There's a request at Openstreetmap-carto to render dual-carriageway roads differently at mid-zoom levels: https://github.com/gravitystorm/openstreetmap-carto/issues/3934 It doesn't appear that there are any tags in the database which hold this information. Ideally one would import a linestring midway between two highway ways, if they were tagged with the same highway class, name, and oneway=yes, but it could be difficult to get this right at locations where the two carriageways separate. Has anyone implemented a rendering that handles dual-carriageway roads, or designed a way to import such ways into a (rendering) database as a single linestring midway between the two OSM ways? - Joseph Eisenberg ___ dev mailing list dev@openstreetmap.org https://lists.openstreetmap.org/listinfo/dev
