Re: [OSM-talk] Key:layer update
Am 13/mar/2014 um 00:28 schrieb Frank Little frank...@xs4all.nl: We model bridges and tunnels in a specific way in OSM which means we do not need to add additional layer tags (but feel free if you do want to). IMHO we do not yet model explicit bridges or tunnels at all, we only add attributes to roads or other objects that they are on a bridge or in a tunnel, but we omit the actual tunnel and bridge objects (besides some few relations that are modeled). cheers, Martin ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 13.03.2014 00:28, Frank Little wrote: Tobias Knerr wrote: http://wiki.openstreetmap.org/wiki/Proposed_features/default_layer_for_bridge_and_tunnel [...] This is however not the implicit layer tags argument which Richard Z. gives, which he suggests means:. so every tunnel and bridge should now have one. That's exactly what was discussed back then. Yes, a mapper who is generally critical of mechanical edits additionally pointed out that such edits might result from a successful vote, but that doesn't change the proposal itself. We model bridges and tunnels in a specific way in OSM which means we do not need to add additional layer tags (but feel free if you do want to). Well, according to the result of the vote, properly mapped bridge/tunnels do need layer tags, and that's what the Key:layer page should document today. I don't see a reason to start the discussion again (especially in this thread), but should you manage to gather broad support for changing the definition, then the Key:layer page may eventually reflect that. I have always understood that we do not use a layer tag for road/waterway crossings, as osm help also suggests here: https://help.openstreetmap.org/questions/3049/how-to-correct-waterways-intersecting-roads-without-a-junction-node That's not what is being suggested here. The option b) in the question was to just add layer=-1 to large sections of a waterway without surveying what actually happens in those places. Which is clearly not a good solution. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Wed, Mar 12, 2014 at 09:06:41PM -0400, Russ Nelson wrote: Pieren writes: On Wed, Mar 12, 2014 at 3:22 PM, Frank Little frank...@xs4all.nl wrote: Richard Z wrote As mapped, the waterway=stream (Way #138911739) runs underground (layer=-1), probably through a culvert given the way the stream left and right are separately outlined as waterway=riverbank (and without layer=*). The way (stream) should be tagged as a culvert. Perhaps there is in reality a bridge not a culvert, in which case the road needs splitting and the appropriate new road segment tagged as bridge=yes. In either case, a layer tag is not needed for rendering. +1 Nonetheless I add one out of habit. But I would be happy to stop, because as noted, the bridge or culvert carries an implicit layering. With a new type of bridge we could do it. The current state is that if there is no layer tag the bridge has a layer=0 which is not what you want. The old definition can't be changed because it would affect many existing crossings. The implicit layering that you mention is a technical workaround that software does to avoid problems with OSM data. Those are not necessarily bugs in OSM data but very often it is missing information - someone was not sure is there a bridge/culvert or perhaps a ford. Rendering and other software needs to make a guess in such cases. Although it might be more correct to paint a question mark there most renderers assume a culvert and implicit layering in such cases. It isn't good to rely on that for technical reasons, many alternative renderers are much less fault tolerant than Mapnik and you will get strange results. Also the validators need to improve their error checking to catch accidental errors and this is nearly impossible until people agree on how to use layer (and level and other similar tags). Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Richard Z wrote In practice this rule is broken more often than you would think: Hamburg is full of waterways connected with roads on bridges through a tag obstacle. France is full of bridges sharing a node with the waterway bellow. ... http://www.openstreetmap.org/node/1522876252 I would say this is an example of incorrect mapping and I would correct it if I came across it on survey. It is either a culvert or a bridge, or a ford. A layer tag should not be necessary in any of these three cases. As mapped, the waterway=stream (Way #138911739) runs underground (layer=-1), probably through a culvert given the way the stream left and right are separately outlined as waterway=riverbank (and without layer=*). The way (stream) should be tagged as a culvert. Perhaps there is in reality a bridge not a culvert, in which case the road needs splitting and the appropriate new road segment tagged as bridge=yes. In either case, a layer tag is not needed for rendering. Given the layer tag, it is unlikely that the mapper thought it was a ford. (I don't know whether the cadastre data distinguishes between these features). Fords do not need layer tag, by definition. The solution will be to find and remap such examples. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Wed, Mar 12, 2014 at 3:22 PM, Frank Little frank...@xs4all.nl wrote: Richard Z wrote As mapped, the waterway=stream (Way #138911739) runs underground (layer=-1), probably through a culvert given the way the stream left and right are separately outlined as waterway=riverbank (and without layer=*). The way (stream) should be tagged as a culvert. Perhaps there is in reality a bridge not a culvert, in which case the road needs splitting and the appropriate new road segment tagged as bridge=yes. In either case, a layer tag is not needed for rendering. +1 Bridge or culvert, one way has to be split (the road for bridge or the stream for culvert) to identify the structure and one of the ways needs a tag layer. It's true that the shared node is wrong here excepted if it's a ford. It needs a local survey. Same mapping issues can be found between roads and railways, railways and rivers, etc Pieren ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Pieren wrote: On Wed, Mar 12, 2014 at 3:22 PM, Frank Little frank...@xs4all.nl wrote: Richard Z wrote As mapped, the waterway=stream (Way #138911739) runs underground (layer=-1), probably through a culvert given the way the stream left and right are separately outlined as waterway=riverbank (and without layer=*). The way (stream) should be tagged as a culvert. Perhaps there is in reality a bridge not a culvert, in which case the road needs splitting and the appropriate new road segment tagged as bridge=yes. In either case, a layer tag is not needed for rendering. +1 Bridge or culvert, one way has to be split (the road for bridge or the stream for culvert) to identify the structure and one of the ways needs a tag layer. It's true that the shared node is wrong here excepted if it's a ford. It needs a local survey. Same mapping issues can be found between roads and railways, railways and rivers, etc Pieren Unless it is a level crossing of road/rail, of course (in which case a tag is needed on the common node, just as with fords). But when did this happen as reported by Richard Z.: QUOTE The initiative to have implicit layer tags for those feature was voted down so every tunnel and bridge should now have one. UNQUOTE ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 12.03.2014 16:53, Frank Little wrote: But when did this happen as reported by Richard Z.: QUOTE The initiative to have implicit layer tags for those feature was voted down so every tunnel and bridge should now have one. UNQUOTE There was a proposal to set default layer=1 for bridge=yes and layer=-1 for tunnel=yes. It was rejected by a clear majority of those who voted: http://wiki.openstreetmap.org/wiki/Proposed_features/default_layer_for_bridge_and_tunnel ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Tobias Knerr wrote: On 12.03.2014 16:53, Frank Little wrote: But when did this happen as reported by Richard Z.: QUOTE The initiative to have implicit layer tags for those feature was voted down so every tunnel and bridge should now have one. UNQUOTE There was a proposal to set default layer=1 for bridge=yes and layer=-1 for tunnel=yes. It was rejected by a clear majority of those who voted: http://wiki.openstreetmap.org/wiki/Proposed_features/default_layer_for_bridge_and_tunnel My thanks. I'd agree with the comment which Frederik Ramm made (while abstaining) on that proposal: If the idea was to automatically add a layer tag to bridges and tunnels (or to remove it if present), I would oppose it (for reasons he gave). This is however not the implicit layer tags argument which Richard Z. gives, which he suggests means:. so every tunnel and bridge should now have one. We model bridges and tunnels in a specific way in OSM which means we do not need to add additional layer tags (but feel free if you do want to). I have always understood that we do not use a layer tag for road/waterway crossings, as osm help also suggests here: https://help.openstreetmap.org/questions/3049/how-to-correct-waterways-intersecting-roads-without-a-junction-node ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Pieren writes: On Wed, Mar 12, 2014 at 3:22 PM, Frank Little frank...@xs4all.nl wrote: Richard Z wrote As mapped, the waterway=stream (Way #138911739) runs underground (layer=-1), probably through a culvert given the way the stream left and right are separately outlined as waterway=riverbank (and without layer=*). The way (stream) should be tagged as a culvert. Perhaps there is in reality a bridge not a culvert, in which case the road needs splitting and the appropriate new road segment tagged as bridge=yes. In either case, a layer tag is not needed for rendering. +1 Nonetheless I add one out of habit. But I would be happy to stop, because as noted, the bridge or culvert carries an implicit layering. Bridge or culvert, one way has to be split (the road for bridge or the stream for culvert) My rule of thumb here is how it looks from above: if the people on the top would perceive it as a bridge, I split that way and mark is as a bridge. Otherwise I split the waterway and mark it as a culvert. -- --my blog is athttp://blog.russnelson.com Crynwr supports open source software 521 Pleasant Valley Rd. | +1 315-600-8815 Potsdam, NY 13676-3213 | Sheepdog ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Could you give some visual examples, maybe temporarily creating them in OSM ( deleting them afterwards) to clarify what you mean? Dave F. On 09/03/2014 22:26, Matthijs Melissen wrote: On 9 March 2014 10:30, Richard Z. ricoz@gmail.com wrote: for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Thank you for doing this, it's very useful to have this properly documented. I have been working on layering in the main CartoCSS stylesheet, and found that at the moment, indeed not all aspects of the layering model are defined precise enough. A question: a single road can contain sections on multiple layers, so there will be a point where the sections that are on different layers meet. At that point, there might even be a side street. However, no vertical ordering should be assumed at such a point. It is written that The vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap. Perhaps 'crossing' should be interpreted here as crossing without node, but that causes problems with bridge/waterway. In other words, I am wondering for each of the following situations if the roads should be interpreted as meeting on the same or different levels: - A node where two waterways on layer 1 and two roads on layer 2 meet; - A node where two roads on layer 1 and two roads on layer 2 meet; - A node where two roads on layer 1 and one road on layer 2 meet; - A node where one road on layer 1 and one road on layer 2 meet. Perhaps some text that answers questions like this should be added to the Wiki-page. -- Matthijs ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Dave F. wrote: Could you give some visual examples, maybe temporarily creating them in OSM ( deleting them afterwards) ... or on the dev server: http://api06.dev.openstreetmap.org/ Cheers, Andy ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09/03/2014 12:21, Richard Z. wrote: the same conceptual problem exists with pylons where they are shared by two bridges or aerial tramways. Actualy every pylon breaks the rule by definition because it connects ground with layer=0 with something else at a different level. How do you want to model such cases better? Lifts in buildings? In practice this rule is broken more often than you would think: Hamburg is full of waterways connected with roads on bridges through a tag obstacle. France is full of bridges sharing a node with the waterway bellow. Could you link to an example please? Dave F. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09/03/2014 14:45, Martin Koppenhoefer wrote: 2014-03-09 13:17 GMT+01:00 Dave F. dave...@madasafish.com mailto:dave...@madasafish.com: it says which object is above and which below when they cross, it is not only for rendering I agree it does say which object is above another. For the benefit of the renderer. Who else needs that data? Certainly not routers. For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. -1, you should not add any layer in this case (tagging for the renderer) The correct expression is 'don't tag incorrectly for the renderer'. There's /nothing/ wrong in making OSM data clearer more accurate. +1, but adding a layer=1 to a lake in a park isn't clearer or more accurate, they are both on the same layer, the lake is in the park, not above (usually). Which confirms my point perfectly. You're are correct: The lake park /are/ at the same level, which is why the layer tag is needed. It's used purely to let the renderer know which entity to put on top of the pile show it display properly. Dave F. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
2014-03-11 15:52 GMT+01:00 Dave F. dave...@madasafish.com: I agree it does say which object is above another. For the benefit of the renderer. Who else needs that data? Certainly not routers. well, everybody who tries to understand what this specific part of the map represents will have to have this information in the case of objects that overlap in 2D. For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. -1, you should not add any layer in this case (tagging for the renderer) The correct expression is 'don't tag incorrectly for the renderer'. There's /nothing/ wrong in making OSM data clearer more accurate. +1, but adding a layer=1 to a lake in a park isn't clearer or more accurate, they are both on the same layer, the lake is in the park, not above (usually). Which confirms my point perfectly. You're are correct: The lake park /are/ at the same level, which is why the layer tag is needed. It's used purely to let the renderer know which entity to put on top of the pile show it display properly. no, it would be wrong to use the layer tag here, as it would move the lake out of the park and above. OK, this sounds unprobable to a human, and he might still understand what was the intention (by interpretation and common sense), but the modelling remains wrong (IMHO). Btw.: a lake is a physical object, while a park is an abstract object, so they aren't on the same level anyway (but on the same layer) ;-) cheers, Martin ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Tue, Mar 11, 2014 at 02:51:23PM +, Dave F. wrote: On 09/03/2014 12:21, Richard Z. wrote: In practice this rule is broken more often than you would think: Hamburg is full of waterways connected with roads on bridges through a tag obstacle. France is full of bridges sharing a node with the waterway bellow. Could you link to an example please? http://www.openstreetmap.org/node/1522876252 stupid question - suppose I have this node selected in JOSM - what is the quickest way of getting an URL like the above? Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Richard Z. schrieb: On Sun, Mar 09, 2014 at 12:34:31PM +, Dave F. wrote: On 09/03/2014 12:24, Richard Z. wrote: it says point, not node the difference probably needs to be emphasized very strongly. There is a difference between mathematicaly precise and intuitive formulations:(( https://www.google.co.uk/#q=node%20definition a point in a network or diagram at which lines or pathways intersect or branch changed to precise location instead of point.. is that better? +1 for location, that's really hard to misinterpret but is clear on what it means. Robert Kaiser ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 10:26:59PM +, Matthijs Melissen wrote: On 9 March 2014 10:30, Richard Z. ricoz@gmail.com wrote: for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Thank you for doing this, it's very useful to have this properly documented. I have been working on layering in the main CartoCSS stylesheet, and found that at the moment, indeed not all aspects of the layering model are defined precise enough. just remembered, there is also a rather special rule for tunnel=building_passage The layer has to be the same as the building, with the above mentioned exception when several tunnels are passing on different levels. https://wiki.openstreetmap.org/wiki/Key:tunnel#tunnel.3Dbuilding_passage It makes sense but is so much different from normal tunnels that I am wondering if it should not have been done with a different tag. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 11/03/2014, Dave F. dave...@madasafish.com wrote: On 09/03/2014 14:45, Martin Koppenhoefer wrote: For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. [...] Which confirms my point perfectly. You're are correct: The lake park /are/ at the same level, which is why the layer tag is needed. It's used purely to let the renderer know which entity to put on top of the pile show it display properly. Go fix your rendering stylesheet if you feel it should display lakes on top of parks but doesn't. Stylesheets make this type of decision for plenty of objects without needing a layer tag. The decision to render a lake on top of a park isn't a universal one. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Tue, Mar 11, 2014 at 02:52:02PM +, Dave F. wrote: On 09/03/2014 14:45, Martin Koppenhoefer wrote: +1, but adding a layer=1 to a lake in a park isn't clearer or more accurate, they are both on the same layer, the lake is in the park, not above (usually). Which confirms my point perfectly. You're are correct: The lake park /are/ at the same level, which is why the layer tag is needed. It's used purely to let the renderer know which entity to put on top of the pile show it display properly. if a layer tag is needed to display a lake in a park then you have some other problem. Show us an example. natural=water + layer has no meaning unless in combination with tunnel, bridge or similar. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
[OSM-talk] Key:layer update
Hi, for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Some of the changes: * the vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap * define layer as higher value means above, lower value means bellow. Avoid the complicated layer=0 definition as the natural ground level as it would be shown by contour lines on a topographic map. Explicit layer=0 seems to be deprecated now. * layer on ways should be used only in combination with one of tunnel=*, bridge=*, highway=steps, highway=elevator, covered=* or indoor=yes. For areas, it could be used in combination with tags such as man_made=bridge, building=* and similar. The motivation for this is to make it easy for validators to spot errors such as when the wrong segment is accidentaly tagged, bridge/tunnel forgotten, or someone tags excessively long ways for no good reason - common problem with waterways and elevated roads/railroads. I have validated this rule for ways in large parts of the world, there are exceptions which currently I do not know hot to tag better but those are rare. * in some cases level may be more appropriate than layer https://wiki.openstreetmap.org/w/index.php?title=Key%3Alayerdiff=999107oldid=935491 Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09/03/2014 10:30, Richard Z. wrote: Hi, for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Some of the changes: * the vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap If you take that literally users will join rivers flowing under a bridge with a node add the layer tag to it, which is incorrect: those ways should not join. * define layer as higher value means above, lower value means bellow. Avoid the complicated layer=0 definition as the natural ground level as it would be shown by contour lines on a topographic map. Explicit layer=0 seems to be deprecated now. * layer on ways should be used only in combination with one of tunnel=*, bridge=*, highway=steps, highway=elevator, covered=* or indoor=yes. For areas, it could be used in combination with tags such as man_made=bridge, building=* and similar. The motivation for this is to make it easy for validators to spot errors such as when the wrong segment is accidentaly tagged, bridge/tunnel forgotten, or someone tags excessively long ways for no good reason - common problem with waterways and elevated roads/railroads. I have validated this rule for ways in large parts of the world, there are exceptions which currently I do not know hot to tag better but those are rare. This is not my understanding of the layer tag. It is a tool to help renderers place objects on top of each other has no real world implication in differences of height. For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. Using multi-polygons is not the solution as it would take the lake /outside/ of the park, so if the renderer didn't want to render it's internal details (playground, wood buildings etc) it would end up with more holes in it than Swiss cheese. Dave F. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 11:47:32AM +0100, Martin Koppenhoefer wrote: Am 09/mar/2014 um 11:30 schrieb Richard Z. ricoz@gmail.com: * the vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap actually at the Point where a layer Way Connects to an layer=0 way both are at the same height (e.g. where a bridge starts) currently the assumption that everything meeting in a node is physically at the same elevation in this point is not valid in OSM. It is broken by definition in at least one case: waterways ar supposed to share a node with the dam they are crossing, which means the highway passing across the dam will also share a node with the river passing thorugh a tunnel or pipeline bellow it. Some objects (such as dam, buildings) have the property to define their own physical level relations. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Am 09/mar/2014 um 12:35 schrieb Dave F. dave...@madasafish.com: This is not my understanding of the layer tag. It is a tool to help renderers place objects on top of each other has no real world implication in differences of height. it has implications on real world topology: it says which object is above and which below when they cross, it is not only for rendering For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. -1, you should not add any layer in this case (tagging for the renderer) cheers, Martin ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Am 09/mar/2014 um 12:43 schrieb Richard Z. ricoz@gmail.com: It is broken by definition in at least one case: waterways ar supposed to share a node with the dam they are crossing, which means the highway passing across the dam will also share a node with the river passing thorugh a tunnel or pipeline bellow it. -1, it is a modeling problem/error, the highway should not have a common node with the waterway, if it has, it is wrong or should be tagged ford=yes ;-) cheers, Martin ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09/03/2014 12:03, Martin Koppenhoefer wrote: Am 09/mar/2014 um 12:35 schrieb Dave F. dave...@madasafish.com: This is not my understanding of the layer tag. It is a tool to help renderers place objects on top of each other has no real world implication in differences of height. it has implications on real world topology: it says which object is above and which below when they cross, it is not only for rendering Disagree. A bridge at the top of Everest would be tagged 'layer=1' exactly as it would be if in Death Valley (86m below sea level) For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. -1, you should not add any layer in this case (tagging for the renderer) The correct expression is 'don't tag incorrectly for the renderer'. There's /nothing/ wrong in making OSM data clearer more accurate. Dave F. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 01:05:18PM +0100, Martin Koppenhoefer wrote: Am 09/mar/2014 um 12:43 schrieb Richard Z. ricoz@gmail.com: It is broken by definition in at least one case: waterways ar supposed to share a node with the dam they are crossing, which means the highway passing across the dam will also share a node with the river passing thorugh a tunnel or pipeline bellow it. -1, it is a modeling problem/error, the highway should not have a common node with the waterway, if it has, it is wrong or should be tagged ford=yes ;-) the same conceptual problem exists with pylons where they are shared by two bridges or aerial tramways. Actualy every pylon breaks the rule by definition because it connects ground with layer=0 with something else at a different level. How do you want to model such cases better? Lifts in buildings? In practice this rule is broken more often than you would think: Hamburg is full of waterways connected with roads on bridges through a tag obstacle. France is full of bridges sharing a node with the waterway bellow. It may be worth to tag have such a rule restricted for ways of the same type and a short well defined list of exceptions. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 11:35:20AM +, Dave F. wrote: On 09/03/2014 10:30, Richard Z. wrote: Hi, for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Some of the changes: * the vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap If you take that literally users will join rivers flowing under a bridge with a node add the layer tag to it, which is incorrect: those ways should not join. it says point, not node the difference probably needs to be emphasized very strongly. There is a difference between mathematicaly precise and intuitive formulations:(( Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 11:35:20AM +, Dave F. wrote: On 09/03/2014 10:30, Richard Z. wrote: Hi, for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Some of the changes: * the vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap If you take that literally users will join rivers flowing under a bridge with a node add the layer tag to it, which is incorrect: those ways should not join. changed the intro text to say The layer=* tag is used to mark vertical relationships between crossing or overlapping features. The vertical ordering established by the layer values is valid exactly only in the point (not node!!!) where the ways cross or objects overlap. Joining the ways with a common node at the point where they cross would destroy the vertical order established by layer. The layer=* is not suitable to define vertical relationships of adjoining or nearby elements or areas. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09/03/2014 12:24, Richard Z. wrote: it says point, not node the difference probably needs to be emphasized very strongly. There is a difference between mathematicaly precise and intuitive formulations:(( https://www.google.co.uk/#q=node%20definition a point in a network or diagram at which lines or pathways intersect or branch Dave F. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09.03.2014 13:17, Dave F. wrote: On 09/03/2014 12:03, Martin Koppenhoefer wrote: it has implications on real world topology: it says which object is above and which below when they cross, it is not only for rendering Disagree. A bridge at the top of Everest would be tagged 'layer=1' exactly as it would be if in Death Valley (86m below sea level) True, but that because layer models *relative* real-world elevation *locally* (between vertically stacked objects), rather than globally. Your statement points out that the layer relationship is neither global nor representative of absolute elevation, but that was never contested. Tobias ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 12:34:31PM +, Dave F. wrote: On 09/03/2014 12:24, Richard Z. wrote: it says point, not node the difference probably needs to be emphasized very strongly. There is a difference between mathematicaly precise and intuitive formulations:(( https://www.google.co.uk/#q=node%20definition a point in a network or diagram at which lines or pathways intersect or branch in OSM this is called node. Better suggestions instead of point? Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09.03.2014 13:21, Richard Z. wrote: the same conceptual problem exists with pylons where they are shared by two bridges or aerial tramways. Actualy every pylon breaks the rule by definition because it connects ground with layer=0 with something else at a different level. How do you want to model such cases better? Lifts in buildings? Typical pylons aren't a problem because the ground is not an OSM element that they could share a node with. Pylons shared between more than one bridge are indeed an interesting problem for 3D mapping, but I'm not aware that this is commonly mapped or used by applications yet, so there is still some room for establishing good standard practice. Lifts in buildings don't use layer, they use level. That tag follows different rules than layer. In practice this rule is broken more often than you would think: Hamburg is full of waterways connected with roads on bridges through a tag obstacle. France is full of bridges sharing a node with the waterway bellow. I would prefer correcting these errors instead of changing the rule they break. It may be worth to tag have such a rule restricted for ways of the same type and a short well defined list of exceptions. The rule is also needed for ways of different types, e.g. for ordering a stack of road, railway, and waterway bridges. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 12:34:31PM +, Dave F. wrote: On 09/03/2014 12:24, Richard Z. wrote: it says point, not node the difference probably needs to be emphasized very strongly. There is a difference between mathematicaly precise and intuitive formulations:(( https://www.google.co.uk/#q=node%20definition a point in a network or diagram at which lines or pathways intersect or branch changed to precise location instead of point.. is that better? Also listed teh pylon as exception. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 02:00:36PM +0100, Tobias Knerr wrote: On 09.03.2014 13:21, Richard Z. wrote: the same conceptual problem exists with pylons where they are shared by two bridges or aerial tramways. Actualy every pylon breaks the rule by definition because it connects ground with layer=0 with something else at a different level. How do you want to model such cases better? Lifts in buildings? Typical pylons aren't a problem because the ground is not an OSM element that they could share a node with. Pylons shared between more than one bridge are indeed an interesting problem for 3D mapping, but I'm not aware that this is commonly mapped or used by applications yet, so there is still some room for establishing good standard practice. Lifts in buildings don't use layer, they use level. That tag follows different rules than layer. I would be in favor of using level more widely but the rules are not so much different because you can also have all kinds of highways and railways on levels. In practice this rule is broken more often than you would think: Hamburg is full of waterways connected with roads on bridges through a tag obstacle. France is full of bridges sharing a node with the waterway bellow. I would prefer correcting these errors instead of changing the rule they break. are those really errors? Pylons must share a node with the waterway bellow in my opinion. They are a pretty relevant part of it. It may be worth to tag have such a rule restricted for ways of the same type and a short well defined list of exceptions. The rule is also needed for ways of different types, e.g. for ordering a stack of road, railway, and waterway bridges. then there is the alternative of having a list of exceptions. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
Not all OSM nodes are also network/diagram nodes, which are points with (AFAIK) three or more lines in common. Intermediate OSM nodes in the middle of a way are not topologically significant. On 2014-03-09 14:00, Richard Z. wrote: On Sun, Mar 09, 2014 at 12:34:31PM +, Dave F. wrote: On 09/03/2014 12:24, Richard Z. wrote: it says point, not node the difference probably needs to be emphasized very strongly. There is a difference between mathematicaly precise and intuitive formulations:(( https://www.google.co.uk/#q=node%20definition [1] a point in a network or diagram at which lines or pathways intersect or branch in OSM this is called node. Better suggestions instead of point? Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk [2] Links: -- [1] https://www.google.co.uk/#q=node%20definition [2] https://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
2014-03-09 13:17 GMT+01:00 Dave F. dave...@madasafish.com: it has implications on real world topology: it says which object is above and which below when they cross, it is not only for rendering Disagree. A bridge at the top of Everest would be tagged 'layer=1' exactly as it would be if in Death Valley (86m below sea level) to me it seems your example does agree with my statement For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. -1, you should not add any layer in this case (tagging for the renderer) The correct expression is 'don't tag incorrectly for the renderer'. There's /nothing/ wrong in making OSM data clearer more accurate. +1, but adding a layer=1 to a lake in a park isn't clearer or more accurate, they are both on the same layer, the lake is in the park, not above (usually). cheers, Martin ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09.03.2014 14:18, Richard Z. wrote: Pylons must share a node with the waterway bellow in my opinion. They are a pretty relevant part of it. Pylons will often be somewhere within the riverbank area - based on their exact positions in reality -, but I would not insert them into the waterway way. What do you do if one pylon is left of the center of the waterway and one is right of it? then there is the alternative of having a list of exceptions. That's more reasonable, but exceptions should only be made where it is really necessary. I haven't encountered such an example yet. Tobias ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 04:55:51PM +0100, Tobias Knerr wrote: On 09.03.2014 14:18, Richard Z. wrote: Pylons must share a node with the waterway bellow in my opinion. They are a pretty relevant part of it. Pylons will often be somewhere within the riverbank area - based on their exact positions in reality -, but I would not insert them into the waterway way. somehow they ought to be connected to the river though, just beeing in the area is not enough. As they are relevant for navigation there can be situations where inserting them into the waterway way would be indeed the most logical solution. What do you do if one pylon is left of the center of the waterway and one is right of it? interesting question.. I will look again at the examples and ask the author. then there is the alternative of having a list of exceptions. That's more reasonable, but exceptions should only be made where it is really necessary. I haven't encountered such an example yet. Having seen a few examples of vertical lifts I am sure there will be more exceptions. Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 09/03/2014, Martin Koppenhoefer dieterdre...@gmail.com wrote: For instance if you had an area tagged 'park' another area within it tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render displayed it. -1, you should not add any layer in this case (tagging for the renderer) The correct expression is 'don't tag incorrectly for the renderer'. There's /nothing/ wrong in making OSM data clearer more accurate. +1, but adding a layer=1 to a lake in a park isn't clearer or more accurate, they are both on the same layer, the lake is in the park, not above (usually). On top of tagging different layers for a park and its lake not being clearer and more accurate, it really is a renderer decision wether to render a park on top of a lake or vice-versa. For example if your rendering of leisure=park is a very transparent green area, then you do want to render it on top of lakes and all other features. So please do not use the layer tag for that purpose. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On 9 March 2014 10:30, Richard Z. ricoz@gmail.com wrote: for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Thank you for doing this, it's very useful to have this properly documented. I have been working on layering in the main CartoCSS stylesheet, and found that at the moment, indeed not all aspects of the layering model are defined precise enough. A question: a single road can contain sections on multiple layers, so there will be a point where the sections that are on different layers meet. At that point, there might even be a side street. However, no vertical ordering should be assumed at such a point. It is written that The vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap. Perhaps 'crossing' should be interpreted here as crossing without node, but that causes problems with bridge/waterway. In other words, I am wondering for each of the following situations if the roads should be interpreted as meeting on the same or different levels: - A node where two waterways on layer 1 and two roads on layer 2 meet; - A node where two roads on layer 1 and two roads on layer 2 meet; - A node where two roads on layer 1 and one road on layer 2 meet; - A node where one road on layer 1 and one road on layer 2 meet. Perhaps some text that answers questions like this should be added to the Wiki-page. -- Matthijs ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Key:layer update
On Sun, Mar 09, 2014 at 10:26:59PM +, Matthijs Melissen wrote: On 9 March 2014 10:30, Richard Z. ricoz@gmail.com wrote: for some time now I have been working on the wiki page to state the rules as clearly as possible.. hope that most of the improvements are fairly uncontroversial. Thank you for doing this, it's very useful to have this properly documented. I have been working on layering in the main CartoCSS stylesheet, and found that at the moment, indeed not all aspects of the layering model are defined precise enough. A question: a single road can contain sections on multiple layers, so there will be a point where the sections that are on different layers meet. At that point, there might even be a side street. However, no vertical ordering should be assumed at such a point. It is written that The vertical ordering established by the layer values is valid exactly only in the point where the ways cross or objects overlap. Perhaps 'crossing' should be interpreted here as crossing without node, but that causes problems with bridge/waterway. it should be indeed crossing without a shared node, have already updated the text to clarify that. In other words, I am wondering for each of the following situations if the roads should be interpreted as meeting on the same or different levels: - A node where two waterways on layer 1 and two roads on layer 2 meet; the roads should join at the same physical level in this node. Except the node is a pylon connecting two bridges on two levels and a waterway or a similarly weird exception which is not described in the wiki but happens in real life and probably somewhere in OSM data as well. Generally, if the node does not have a special type (lift, pylon, part of buildings with level) the roads should join as expected. Nothing is certain about the waterway unless the node is of type ford or pylon, or the layering is otherwise obvious such as when the road is on a dam or weir. Exceptions and errors in data are currently very common where waterways and roads have shared nodes. Once I have mapped a weir with a highway ford on top it and part of the water going through a pipe through the weir. Conceptually I am thinking of it so that certain constructions such as a dam establish a connection in the sense that both the road and the river are passing over/through it and hence are connected to the dam without really meeting in this point - the dam establishes its own layering rules. - A node where two roads on layer 1 and two roads on layer 2 meet; - A node where two roads on layer 1 and one road on layer 2 meet; - A node where one road on layer 1 and one road on layer 2 meet. they should all join without steps and exceptions should be extremely rare.(maybe lifts and such) More precisely layer does not say anything in this situation so the default rule applies - roads are expected to join without steps. It is important to understand that the meaning of layer is very limited: - it applies exactly only in the point (without shared node) of the crossing and has absolutely no meaning anywhere else - it has absolutely no defined meaning if not in combination with one of bridge, tunnel and the other tags listed in the wiki (I may have forgotten some but you get an idea) - a number of other tags (covered, location, level, dam and probably some other) define own layering concepts or modify layer in strange ways Richard ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
