Re: [Tagging] Rivers classification
W dniu 07.08.2017 o 00:15, Lukas Sommer pisze: Both, Wisła (http://www.openstreetmap.org/relation/34392) and Czerwona (http://www.openstreetmap.org/way/269561538) have the classic stream order “1” just before they enter in the ocean. Likely, the former you would like to render on low zoom levels, the latter not. So I don’t understand how the stream order number could help here. order:classic=1 can be a basic filter - if there's a river with "2", we can safely skip it and take the next one link - river that goes directly to a sea, because it's (by definition) bigger. It's a relative system which can be fine tuned with some other data. Note that for Strahler that’s a similar problem: “Higher number” means “yet more other rivers that have joint the current river and now it’s bigger than before”, but that says nothing (in absolute terms) about how large the river is, neither about how important it is neither about how long it is and neither about it can be used by big ships. For each river system, you would need an own threeshold to make useful rendering. I see this awkward… We already use some custom thresholds on osm-carto for rendering cities or filtering out small areas for example. But the bigger problem with "top down" approach is that it may need recomputations and data about the waterways network can be hard to find. Something more similar to the roads hirarchy is CEMT, because it has a fixed and limited number of allowed values and is directly related to (ship) traffic, while stream order numbers by definetion are integers that do not have a maximum limit and don’t tell is if big (or small) ships can use this river. Wikipedia says, Shreve correlates more or less with the amount of water, so this might be the only stream order number that might help us. On the other side, it will likely correlate also with the yet existing width=* value. CEMT is limited to Europe, as you know, but we can also use this as an additional data. There are also some other data I think we could use: - width at the river mouth - length/area of the basin (they are correlated - see: https://en.wikipedia.org/wiki/Hack%27s_law) It all needs some testing, but we need some values to be tagged first. -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
W dniu 06.08.2017 o 23:42, Colin Smale pisze: The problem I see with some of these stream models is that we are starting from the big rivers with no mapping of tributaries in many cases. As detail gets added, it looks like the ratings of all the downstream segments will need to be recomputed. This is a practical problem I see with Strahler/Shreve classifications. It would be great if we could check the facts about the rivers somewhere else instead of recalculating based on adding more waterways, but I'm not sure where we could find such sources. > If there is a system that starts with a "1" for the estuary and uses increasing values as you go upstream and pass confluences, that would minimise the recomputations required. Order:classic starts with "1" and and it's easy to compute it just once. Maybe drainage basin area or length could be used to further determine how important given river is. -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
We have a hierarchy of "importance" for roads, why not for waterways as well? It's like we have nothing between motorway (river) and unclassified (stream). The problem I see with some of these stream models is that we are starting from the big rivers with no mapping of tributaries in many cases. As detail gets added, it looks like the ratings of all the downstream segments will need to be recomputed. If there is a system that starts with a "1" for the estuary and uses increasing values as you go upstream and pass confluences, that would minimise the recomputations required. //colin On 2017-08-06 23:19, Richard wrote: > On Sun, Aug 06, 2017 at 05:30:20PM +0200, Daniel Koć wrote: W dniu 06.08.2017 > o 13:32, Richard pisze: as of rendering, respecting river width and doing > something reasonable > with intermittent flows would be a great progress. > What's the problem with intermittent flows? I'm not familiar with water > tagging. > > River width is a local property - it can vary lot in different places. I > need simple, synthetic measure for lower zoom levels (like > country/continent) without making any computations. The width is fine for many small rivers where mapping riverbanks would be a nonsense and should be respected by the renderer. But what you ask for seems like tagging for the renderer. Most of the information is already there, either river width or the geometry determined by riverbanks. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
W dniu 06.08.2017 o 23:19, Richard pisze: The width is fine for many small rivers where mapping riverbanks would be a nonsense and should be respected by the renderer. But what you ask for seems like tagging for the renderer. Most of the information is already there, either river width or the geometry determined by riverbanks. Using classification is not tagging for the renderer, because it's not cheating that it's something different - it's just simplifying and sorting. It's a useful generalization, just like having different types of roads as a general property. Highways of course have width too and you can also draw the geometry with area:highway=*, but that's a different thing. On the macro scale you don't want all the details, only general data. -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
On Sun, Aug 06, 2017 at 05:30:20PM +0200, Daniel Koć wrote: > W dniu 06.08.2017 o 13:32, Richard pisze: > >as of rendering, respecting river width and doing something reasonable > >with intermittent flows would be a great progress. > > What's the problem with intermittent flows? I'm not familiar with water > tagging. > > River width is a local property - it can vary lot in different places. I > need simple, synthetic measure for lower zoom levels (like > country/continent) without making any computations. The width is fine for many small rivers where mapping riverbanks would be a nonsense and should be respected by the renderer. But what you ask for seems like tagging for the renderer. Most of the information is already there, either river width or the geometry determined by riverbanks. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
W dniu 06.08.2017 o 19:07, Lukas Sommer pisze: [You have replied to me personally, but I guess it should go to the list] I would encourage to use only _one_ classification system. Otherwise, the tagging will be _very_ complex and using it for rendering nearly to impossible, because it will be impossible to compare between different classification systems. 3 main systems are used in cartography for different things (see the Wikipedia article): - [order:classic] is suitable for general cartographic purposes [...]. The first order stream is the one which, at each confluence, is the one with the greatest volumetric flow, which usually reflects the long-standing naming of rivers. - [order:strahler] is designed for the morphology of a catchment and forms the basis of important hydrographical indicators of its structure, such as bifurcation ratio, drainage density and frequency. - [order:shreve] is preferred in hydrodynamics: it sums the number of sources in each catchment above a stream gauge or outflow, and correlates roughly to the discharge volumes and pollution levels. Adding optional tag does not make anything hard, it just allows to use our database for more purposes, including hydrographic maps and analysis. I don't think we should encourage any of them, because there's no "the best" classification system. It seems to me that “stream order” means basically “level of branching”. This information is almost useless for rendering at openstreetmap-carto, because you can have a high level of branching even on very small rivers, and you can also have a very low level of branching on very large rivers. What’s interesting for rendering is in my opinion rather the width of a river. The key “CEMT” seems to me the better choise here (but seems to be europe-centric), but also the “width” key might help and is likely to be found all over the world. For general rendering on low zoom I would probably use combination of classic and Strahler/Shreve. order:classic=1 means only that this river goes to the sea, which is more important than the river with higher number, but order:strahler/order:shreve=1 means also that it's not important river anyway. -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] service=access
You're probably right Gerd. I sometimes get too enthusiastic about adding tags to objects. The access tag is probably completely unnecessary. Still, I'm curious about why other mappers decided to use it. On Sat, Aug 5, 2017 at 8:49 PM, Gerd Petermann < gpetermann_muenc...@hotmail.com> wrote: > Hi Dave, > > my understanding is that most hw=service are used to access a specific > man_made object, so this tag > seems to be superfluous to me. I would simply not use the service tag here. > > Gerd > > Von: Dave Swarthout > Gesendet: Samstag, 5. August 2017 23:02:18 > An: Tag discussion, strategy and related tools > Betreff: [Tagging] service=access > > Hi, > > I'm working on highway tagging in Alaska and am developing a preset to > automate the tagging of the many gravel service roads that are used to > access the Trans-Alaska Pipeline (TAP). I have never used the > service=access tag and there is nothing in the Wiki about it but it would > seem to be an ideal tag to use in my work because those roads are being > used to get close to the TAP, in other words, to access it. Taginfo shows > about 600 uses of the tag and most of those appear to be for unpaved > service roads similar to the ones I'm seeing in my work. > > However, seeing as no documentation of the tag exists, I'm wondering if > any of you have used this tag or have some insights to offer. > > As always, thanks in advance. > > Dave > > > > -- > Dave Swarthout > Homer, Alaska > Chiang Mai, Thailand > Travel Blog at http://dswarthout.blogspot.com > -- Dave Swarthout Homer, Alaska Chiang Mai, Thailand Travel Blog at http://dswarthout.blogspot.com ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
W dniu 06.08.2017 o 13:32, Richard pisze: as of rendering, respecting river width and doing something reasonable with intermittent flows would be a great progress. What's the problem with intermittent flows? I'm not familiar with water tagging. River width is a local property - it can vary lot in different places. I need simple, synthetic measure for lower zoom levels (like country/continent) without making any computations. Stream order classification (or rather "waterway order" in our case) is very good for this, but it has few different versions, mainly (according to Wikipedia): - classic stream order (also called Hack's stream order or Gravelius' stream order), - Strahler stream order (also Strahler number or Horton–Strahler number), - Shreve stream order (with Hodgkinson et al.) but also topological stream order system and probably some other too. We should allow any of them to be used, so a general namespace should be crafted. It could look like: 1. order:x - order:classic (or order:hack or order:gravelius), - order:strahler, - order:shreve, - order:topologic(al) 2. waterway:order:x 3. waterway_order:x (or stream_order:x or waterbody_order:x) 4. waterway:class:x (or waterway_class:x) and possibly others. What do you think about it? Iirc the stream order issue has been brought up on some talk page previously. Thanks, but it's just a brief mention: https://wiki.openstreetmap.org/wiki/Talk:Key:waterway#Stream_Order -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
(Wrong title sorry, here it is again) There is the CEMT tag, but I guess it's only useful for Europe: http://wiki.openstreetmap.org/wiki/Key:CEMT Janko ned, 6. kol 2017. u 13:34 Richard napisao je: > On Sun, Aug 06, 2017 at 11:26:23AM +0200, Daniel Koć wrote: > > I was thinking about better rendering rivers on medium and low zoom > levels > > of osm-carto and I've found that we lack any classification of them - > > anything bigger than stream is just a river. > > as of rendering, respecting river width and doing something reasonable > with intermittent flows would be a great progress. > Iirc the stream order issue has been brought up on some talk page > previously. > > Also had a look at natural=riverbed which at this stage has some > problems. > > Richard > > ___ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
[Tagging] Odg: Rivers classification
There is the CEMT tag, but I guess it's only usefull for Europe: http://wiki.openstreetmap.org/wiki/Key:CEMT Janko Pošiljatelj: Daniel Koć Poslano:6. kolovoza 2017. 11:28 Primatelj: Tagging@openstreetmap.org Predmet: [Tagging] Rivers classification I was thinking about better rendering rivers on medium and low zoom levels of osm-carto and I've found that we lack any classification of them - anything bigger than stream is just a river. There are no suitable tags defined: https://wiki.openstreetmap.org/wiki/Tag:waterway%3Driver and no such tags in database too: https://taginfo.openstreetmap.org/tags/waterway=river#combinations There are some waterway classification systems used in cartography: https://en.wikipedia.org/wiki/Stream_order#Usage but how should we tag them? -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Rivers classification
On Sun, Aug 06, 2017 at 11:26:23AM +0200, Daniel Koć wrote: > I was thinking about better rendering rivers on medium and low zoom levels > of osm-carto and I've found that we lack any classification of them - > anything bigger than stream is just a river. as of rendering, respecting river width and doing something reasonable with intermittent flows would be a great progress. Iirc the stream order issue has been brought up on some talk page previously. Also had a look at natural=riverbed which at this stage has some problems. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
[Tagging] Rivers classification
I was thinking about better rendering rivers on medium and low zoom levels of osm-carto and I've found that we lack any classification of them - anything bigger than stream is just a river. There are no suitable tags defined: https://wiki.openstreetmap.org/wiki/Tag:waterway%3Driver and no such tags in database too: https://taginfo.openstreetmap.org/tags/waterway=river#combinations There are some waterway classification systems used in cartography: https://en.wikipedia.org/wiki/Stream_order#Usage but how should we tag them? -- "Like a halo in reverse" [M. Gore] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
