Re: [Tagging] natural=bay as nodes are evil
Could we try an example to see whether mappers agree on bay areas ? could you draw the Gulf of Biscay on a map ? This guy did it : http://1.bp.blogspot.com/_-9_Y031ZiZQ/THowBMn81dI/Ci8/inSvDDa1DC4/s1600/Golf+van+Biskaje.jpg I might have extended it a bit further to the west on the Spanish coast... regards m On Wed, Oct 29, 2014 at 6:12 PM, moltonel 3x Combo molto...@gmail.com wrote: On 29/10/2014, Richard Z. ricoz@gmail.com wrote: On Tue, Oct 28, 2014 at 05:21:06PM +0100, moltonel 3x Combo wrote: On 28/10/2014, Richard Z. ricoz@gmail.com wrote: well even if the issues were nonexistent, mapping the area of a bay seems to me like mapping an artificially introduced concept for which there is very little real world use or recognition otherwise. Huh ? Forget about maps and osm for a moment. A bay is a body of water mostly surrounded by land. You're in a bay, not at a bay. It has a size, it's not a point in space with a buoy marking the spot. It's an area. The fact that a lot of sources have simplified it down to a point is an entirely different issue. But there's no reason that, with modern tools and manpower, we can't make a better job than those historical sources. And remember that when you see a rendered bay label, you don't actually know wether the source (wether it's some vector data or an idea in the sailor's brain) was an area or a point to begin with. Also bays with very flat or deep geometry will result in disproportionately small areas so mappers may feel compelled to do some ugly workarounds if the name of the bay isn't shown as expected. Disproportionate compared to what ? And fairly flat coastlines are a good example of cases that are tricky for algorythms, where the human mapper can probably make a better decision. So I would say * if there is some other reason valid to map the bay as area, do it pros: - bays are areas in real life - it makes geocoding trivial - it makes knowing which bays to render preferably easy (bigger bays first) - it enables representing nested bays - it is deterministic, as opposed to relying on a heuristic algorythm cons: - relations are harder to work with than nodes - the extent of bays is usually fuzzy; nodes make that fuzzyness obvious - most of the existing data (osm and potential imports) are nodes YMMV, those are reasons enough for me. * something better needs to be invented for hinting the renderer. It's not just the renderer, I actually think that the geocoding usacase is more important. And geocoding requires an area, wether it is provided in readily-usable form as osm data, or by a heuristics-based algorythm that infers it from a node. ___ 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] natural=bay as nodes are evil
A lot of the bay points were imported. Many bays do not have firm boundaries. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Thu, Oct 30, 2014 at 08:41:18AM +0100, Marc Gemis wrote: Could we try an example to see whether mappers agree on bay areas ? could you draw the Gulf of Biscay on a map ? This guy did it : http://1.bp.blogspot.com/_-9_Y031ZiZQ/THowBMn81dI/Ci8/inSvDDa1DC4/s1600/Golf+van+Biskaje.jpg I might have extended it a bit further to the west on the Spanish coast... note that the big bodies of water such as the bay of biscay have been defined by the international hydropgraphic organization, wikipedia provides the link. Those definitions should be probably mapped, but most likely with a special tag rather than our natural=bay because their definition of gulf of mexico is obviously not compatible with our definition of bay (refering to the sentence fragment in Cuba, through this island to the meridian of 83°W which includes a landmas to the definition) Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 30.10.2014 12:51, Richard Z. wrote: their definition of gulf of mexico is obviously not compatible with our definition of bay IMHO: this has some similarities to definition of regions like the Alps or the Rocky Mountains... Cheers, Michael. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Thu, 30 Oct 2014, Marc Gemis wrote: Could we try an example to see whether mappers agree on bay areas ? could you draw the Gulf of Biscay on a map ? This guy did it: http://1.bp.blogspot.com/_-9_Y031ZiZQ/THowBMn81dI/Ci8/inSvDDa1DC4 /s1600/Golf+van+Biskaje.jpg I might have extended it a bit further to the west on the Spanish coast... Would it be possible that locals around that region of the coastline would know it better than tagging@ ? ...If so, then the usual argument for OSM taking advantage of mappers' local knowledge applies also here and we should defer determining that boundary point more accurately to a local mapper. -- i.___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
I think this appears to be the reference Richard mentioned: http://www.iho-ohi.net/iho_pubs/standard/S-23/S23_1953.pdf On Thu, Oct 30, 2014 at 6:51 AM, Richard Z. ricoz@gmail.com wrote: On Thu, Oct 30, 2014 at 08:41:18AM +0100, Marc Gemis wrote: Could we try an example to see whether mappers agree on bay areas ? could you draw the Gulf of Biscay on a map ? This guy did it : http://1.bp.blogspot.com/_-9_Y031ZiZQ/THowBMn81dI/Ci8/inSvDDa1DC4/s1600/Golf+van+Biskaje.jpg I might have extended it a bit further to the west on the Spanish coast... note that the big bodies of water such as the bay of biscay have been defined by the international hydropgraphic organization, wikipedia provides the link. Those definitions should be probably mapped, but most likely with a special tag rather than our natural=bay because their definition of gulf of mexico is obviously not compatible with our definition of bay (refering to the sentence fragment in Cuba, through this island to the meridian of 83°W which includes a landmas to the definition) 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] natural=bay as nodes are evil
On Tue, Oct 28, 2014 at 05:21:06PM +0100, moltonel 3x Combo wrote: On 28/10/2014, Richard Z. ricoz@gmail.com wrote: On Tue, Oct 28, 2014 at 11:18:43AM +0100, Martin Koppenhoefer wrote: 2014-10-28 10:57 GMT+01:00 Richard Z. ricoz@gmail.com: The assumption is that a large bay will typically be more important than a smaller bay. For a good rendering you'd show only the more important bay names in medium zoom level and show the less important ones in higher zoom levels. You would use the size to decide which name to omit in case you'd not have space to render all of them. so to decide which label should be bigger or rendered at lower zoom level you would suggest to: * map bays as areas, with all previously mentioned issues The issues are real, but we disagree on how big they are. I'm of the opinion that they aren't worth fussing over, but YMMV. well even if the issues were nonexistent, mapping the area of a bay seems to me like mapping an artificially introduced concept for which there is very little real world use or recognition otherwise. Also bays with very flat or deep geometry will result in disproportionately small areas so mappers may feel compelled to do some ugly workarounds if the name of the bay isn't shown as expected. So I would say * if there is some other reason valid to map the bay as area, do it * something better needs to be invented for hinting the renderer. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-29 14:40 GMT+01:00 Richard Z. ricoz@gmail.com: Also bays with very flat or deep geometry will result in disproportionately small areas so mappers may feel compelled to do some ugly workarounds if the name of the bay isn't shown as expected. disproportionate to what? water depth really doesn't matter at all in this context (IMHO) cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-29 14:46 GMT+01:00 Martin Koppenhoefer dieterdre...@gmail.com: 2014-10-29 14:40 GMT+01:00 Richard Z. ricoz@gmail.com: Also bays with very flat or deep geometry will result in disproportionately small areas so mappers may feel compelled to do some ugly workarounds if the name of the bay isn't shown as expected. disproportionate to what? water depth really doesn't matter at all in this context (IMHO) I think he was talking about bay shapes: http://i.imgur.com/AMigrSf.png What if we mapped bays on coastlines, and then the renderer can connect the ending points with a straight line or a curve. And we can combine that with a node which can be something like place=country (a rendering hint). Janko ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 28/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: On Tuesday 28 October 2014, moltonel 3x Combo wrote: I admit I don't fully understand how your algorythm works. I can't imagine how you reduce everything to nodes and still retain information about orientation and curves. Can you change your rendering to display the infered polygons instead of the name ? I do not infer any areas, i just generate curves (splines) based on the nodes and the surrounding coastlines and place the text along them. Hum, so that's only usable for label rendering, not geocoding :/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 29/10/2014, Richard Z. ricoz@gmail.com wrote: On Tue, Oct 28, 2014 at 05:21:06PM +0100, moltonel 3x Combo wrote: On 28/10/2014, Richard Z. ricoz@gmail.com wrote: well even if the issues were nonexistent, mapping the area of a bay seems to me like mapping an artificially introduced concept for which there is very little real world use or recognition otherwise. Huh ? Forget about maps and osm for a moment. A bay is a body of water mostly surrounded by land. You're in a bay, not at a bay. It has a size, it's not a point in space with a buoy marking the spot. It's an area. The fact that a lot of sources have simplified it down to a point is an entirely different issue. But there's no reason that, with modern tools and manpower, we can't make a better job than those historical sources. And remember that when you see a rendered bay label, you don't actually know wether the source (wether it's some vector data or an idea in the sailor's brain) was an area or a point to begin with. Also bays with very flat or deep geometry will result in disproportionately small areas so mappers may feel compelled to do some ugly workarounds if the name of the bay isn't shown as expected. Disproportionate compared to what ? And fairly flat coastlines are a good example of cases that are tricky for algorythms, where the human mapper can probably make a better decision. So I would say * if there is some other reason valid to map the bay as area, do it pros: - bays are areas in real life - it makes geocoding trivial - it makes knowing which bays to render preferably easy (bigger bays first) - it enables representing nested bays - it is deterministic, as opposed to relying on a heuristic algorythm cons: - relations are harder to work with than nodes - the extent of bays is usually fuzzy; nodes make that fuzzyness obvious - most of the existing data (osm and potential imports) are nodes YMMV, those are reasons enough for me. * something better needs to be invented for hinting the renderer. It's not just the renderer, I actually think that the geocoding usacase is more important. And geocoding requires an area, wether it is provided in readily-usable form as osm data, or by a heuristics-based algorythm that infers it from a node. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Tuesday 28 October 2014, Janko Mihelić wrote: If you want to formulate a formal mathematical rule for where the node for a bay is best placed: Place it so the variance of the distance of the node to the bay's shores is minimized. Most existing nodes comply with this rule remarkably well. What's the best place for the node in Guantanamo Bay? Is the current node well placed? I'd say it is. Note the algorithm i sketched in its simple form would seriously underestimate the bay size due to the peninsula in the middle - same problem as small islands in the bay which i already mentioned. It is fairly easy though to detect and fix this (by making use of the fact that a bay is 'mostly surrounded by land'). On a general note the established tagging conventions are of course not well suited for tropical coastal landforms dominated by mangrove. Technically you might also consider the inner bay a lagoon rather than a bay. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Mon, Oct 27, 2014 at 04:28:53PM -0400, Eric Kidd wrote: But the key point here is that none of these official sources represent bays as polygons. GNIS uses a pointssomewhere in the bay. The nautical charts print the name somewhere in the middle of the bay. Effectively, the official data really is a point, plus whatever guesswork a human reader supplies. +1 Also, I am reading the arguments about estimating bay area so I am curious - when was the last time someone asked about bay area in square kilometers? I think it makes only sense in the context of territorial waters, fishing or mining rights etc. In such cases there will be an officially supplied boundary that can be used but will not necessarily agree with traditional extent of the bay. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-28 10:57 GMT+01:00 Richard Z. ricoz@gmail.com: Also, I am reading the arguments about estimating bay area so I am curious - when was the last time someone asked about bay area in square kilometers? I think it makes only sense in the context of territorial waters, fishing or mining rights etc. The assumption is that a large bay will typically be more important than a smaller bay. For a good rendering you'd show only the more important bay names in medium zoom level and show the less important ones in higher zoom levels. You would use the size to decide which name to omit in case you'd not have space to render all of them. Territorial waters are at most loosely connected to bays, because you don't use the coastline to determine them, you use the baseline. Cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Tue, Oct 28, 2014 at 11:18:43AM +0100, Martin Koppenhoefer wrote: 2014-10-28 10:57 GMT+01:00 Richard Z. ricoz@gmail.com: Also, I am reading the arguments about estimating bay area so I am curious - when was the last time someone asked about bay area in square kilometers? I think it makes only sense in the context of territorial waters, fishing or mining rights etc. The assumption is that a large bay will typically be more important than a smaller bay. For a good rendering you'd show only the more important bay names in medium zoom level and show the less important ones in higher zoom levels. You would use the size to decide which name to omit in case you'd not have space to render all of them. so to decide which label should be bigger or rendered at lower zoom level you would suggest to: * map bays as areas, with all previously mentioned issues * design a sophisticated computer algorithm to calculate the size of bays and derive bay importance from this Wow.. masterpiece of mapping for the renderer I would say. There must be easier ways of achieving this. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Tue, 28 Oct 2014, Christoph Hormann wrote: On Tuesday 28 October 2014, Janko Mihelić wrote: If you want to formulate a formal mathematical rule for where the node for a bay is best placed: Place it so the variance of the distance of the node to the bay's shores is minimized. Most existing nodes comply with this rule remarkably well. What's the best place for the node in Guantanamo Bay? Is the current node well placed? I'd say it is. Note the algorithm i sketched in its simple form would seriously underestimate the bay size due to the peninsula in the middle - same problem as small islands in the bay which i already mentioned. It is fairly easy though to detect and fix this (by making use of the fact that a bay is 'mostly surrounded by land'). I see. This underestimation in the peninsula case was why I though you'd want the nodes at the entry point and thus my earlier comment about natural=bay_entry. But are all bays 'mostly surrounded by land' or do some bays also have very wide entrypoints (in addition to two pockets to trigger this peninsula case)? And yes, I know it can always be solved by drawing area manually if the algorithm won't get it right. Btw, instead of huge and fragile areas we could just create a relation which holds the coastline nodes of the bay extreme end points. Although also that would probably be just as fuzzy as the outer edge would be (i.e., where the bay really would end along the coastline). -- i.___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 27/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: Since for label rendering you don't really need a polygon there is little point in actually generating it in the first place. But i have implemented and used techniques not unlike the algorithm described for rendering bay and strait labels, like in http://maps.imagico.de/#map=3/80.707/55.862lang=enl=darkr=fjui=0 That's actually a very nice rendering. The channels in particular seem to be oriented very naturally. But when I look at the underlying osm data (nodes), it is much less clear how those features are oriented. I feel like the rendering tricked me into thinking that's it, the channel is laid out this way when the actual data says nothing of the sort. To render a pretty picture, I'd certainly use something like that. To implement geofencing, area calculations, etc, I'd much rather trust a human-estimated area. The funny thing is the first thing i do for this is reduce all features mapped as polygons to a node since the polygon is useless, its outer limit is arbitrary and the sides defined by the coastline do not match the generalized coastline used to render the map. I admit I don't fully understand how your algorythm works. I can't imagine how you reduce everything to nodes and still retain information about orientation and curves. Can you change your rendering to display the infered polygons instead of the name ? ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 28/10/2014, Richard Z. ricoz@gmail.com wrote: On Tue, Oct 28, 2014 at 11:18:43AM +0100, Martin Koppenhoefer wrote: 2014-10-28 10:57 GMT+01:00 Richard Z. ricoz@gmail.com: The assumption is that a large bay will typically be more important than a smaller bay. For a good rendering you'd show only the more important bay names in medium zoom level and show the less important ones in higher zoom levels. You would use the size to decide which name to omit in case you'd not have space to render all of them. so to decide which label should be bigger or rendered at lower zoom level you would suggest to: * map bays as areas, with all previously mentioned issues The issues are real, but we disagree on how big they are. I'm of the opinion that they aren't worth fussing over, but YMMV. * design a sophisticated computer algorithm to calculate the size of bays and derive bay importance from this Finding the size of an area is actually much simpler than your proposed algorythm. It's implemented in stock PostGIS. It doesn't involve tuning or heuristics. It's aready used in many places in the default osm rendering (osm-carto). It is done at import time and is free from the map designer's POV. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Tuesday 28 October 2014, Ilpo Järvinen wrote: But are all bays 'mostly surrounded by land' or do some bays also have very wide entrypoints (in addition to two pockets to trigger this peninsula case)? And yes, I know it can always be solved by drawing area manually if the algorithm won't get it right. The wiki defines bays as Area of water mostly surrounded by land. There are quite a few cases tagged this way with only a slight dent in an otherwise flat coastline where - if you'd map them as an area - less than half of the area outline would be formed by coastline. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Tuesday 28 October 2014, moltonel 3x Combo wrote: That's actually a very nice rendering. The channels in particular seem to be oriented very naturally. But when I look at the underlying osm data (nodes), it is much less clear how those features are oriented. I feel like the rendering tricked me into thinking that's it, the channel is laid out this way when the actual data says nothing of the sort. For a channel between two islands with simple convex shape the situation is actually much clearer than for a bay - it is a one-dimensional feature, it has a width but no length so mapping it as an area is plainly wrong. In more complicated situations the established method is to use a way connecting a few key points - up to extreme cases like here: http://www.openstreetmap.org/way/163242449 I admit I don't fully understand how your algorythm works. I can't imagine how you reduce everything to nodes and still retain information about orientation and curves. Can you change your rendering to display the infered polygons instead of the name ? I do not infer any areas, i just generate curves (splines) based on the nodes and the surrounding coastlines and place the text along them. The main problem is that spatial database systems are not well suited for this kind of work (i.e. tasks like 'find the closest coastline in a certain direction'). -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 26.10.2014 17:12, Mateusz Konieczny wrote: Please, try mapping bays as areas - not as nodes. but if you - for whatever reason ever - can't map it as area then it's better to map it as node instead not mapping it at all... Just an example: I did it some times ago with something (can't remember what ist was, at least not a bay but maybe an amenity). And IIRC it was simply due to missing time at this edit. To be honest: I returned to work on this region some weeks later and changed the node to an area. So of course an area is usually better than a node. Just my 2 cents, Michael. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 26/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: I don't see what information is missing and cannot be easily determined automatically with a properly placed node that is contained in an area - except for the outer edge of course, which is usually ill-defined though as you said yourself. If you think about it a bit and do not try to place the node where you would place the label (which depends on the map projection anyway) properly placing a node for a bay is usually quite simple. The most difficult are long, fjord-like bays where a way along them would be more appropriate. I'm really curious what your method to figure out the bay area from the node is, because even as a human I find that most bay nodes can lead to many different interpretations. A computer algorythm would probably get it wrong most of the time. Think back to the bays within bays situation. How far along the coast do this bay extend ? Are those two nearby nodes separate bays or overlapping ones ? The situation is even harder to gauge when there is no imagery to give a sense of scale. I'm sure most mappers just put the node where they'd put the label (blissfully ignoring scales and projections). Bays-as-polygons bring real value by sorting out this mess. Specific arguments aside - i am not sure if you realize the consequences it would have if subareas of oceans would generally be mapped as polygons - large bays usually contain smaller bays and are parts of a sea and there might be a strait between an island and the coast within that bay. If you want to edit the coastline in such situation you would end up having to deal with a handful of convoluted multipolygon relations, some of them of colossal size. Properly editing coastlines is difficult for beginners in the first place. This would make it borderline impossible. Some coastline ways would belong to more relations, so what ? They already usually belong to 3-4 administrative boundary relations, adding 1-2 bays won't make a big difference. I'm tired of the multipolygons are complicated, avoid them argument, it should be multipolygons are complicated, make them simpler. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-26 17:12 GMT+01:00 Mateusz Konieczny matkoni...@gmail.com: Please, try mapping bays as areas - not as nodes. +1. Please do this also for place=country and other place objects that are indeed describing polygons and not points. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-26 19:00 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: Doable for sure but an awfully bad idea, mapping bays as areas would mean two features for the same object (coastline polygon and bay area). I don't see one object. There is a coastline (linear division between land and sea, NOT a polygon itself) and there is a bay (polygon of a part of the sea). ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-26 21:38 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: Specific arguments aside - i am not sure if you realize the consequences it would have if subareas of oceans would generally be mapped as polygons - large bays usually contain smaller bays and are parts of a sea and there might be a strait between an island and the coast within that bay. If you want to edit the coastline in such situation you would end up having to deal with a handful of convoluted multipolygon relations, some of them of colossal size. yes, you'd end up with nested multipolygons, some of the huge (the latter might become a problem). On the other hand it is clear that nodes don't convey any of the hirarchy or size information and hence are a poor representation. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
I had a proposal about mapping peninsulas [1] and it involved adding peninsula=* tags to coastlines. I think bays should be mapped the same way, on coastline ways. The question is what tags we should use. Adding new ways and gluing them to coastlines, when coastlines themselves make a bay is in my opinion superfluous. [1] http://wiki.openstreetmap.org/wiki/Proposed_features/Peninsula Janko Mihelić 2014-10-27 11:03 GMT+01:00 Martin Koppenhoefer dieterdre...@gmail.com: 2014-10-26 21:38 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: Specific arguments aside - i am not sure if you realize the consequences it would have if subareas of oceans would generally be mapped as polygons - large bays usually contain smaller bays and are parts of a sea and there might be a strait between an island and the coast within that bay. If you want to edit the coastline in such situation you would end up having to deal with a handful of convoluted multipolygon relations, some of them of colossal size. yes, you'd end up with nested multipolygons, some of the huge (the latter might become a problem). On the other hand it is clear that nodes don't convey any of the hirarchy or size information and hence are a poor representation. ___ 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] natural=bay as nodes are evil
On Sun, 26 Oct 2014, Christoph Hormann wrote: On Sunday 26 October 2014, Mateusz Konieczny wrote: Furthermore the outer edge of a bay, i.e. the edge that is not coastline is usually not well defined and would require an arbitrary cutoff. Yes, cutoff is unfortunately quite arbitrary. But node placement is completely arbitrary - and lacks important information. I don't see what information is missing and cannot be easily determined automatically with a properly placed node that is contained in an area - except for the outer edge of course, which is usually ill-defined though as you said yourself. Any data consumer could quite easily, if not trivially, detect that fuzzy edge in this case if it cares about it in the first place (I've have some trouble in figuring out a sensible use case in which it would make a difference to know where the fuzzy border of a bays is). Besides, we really need to deal with object that have fuzzy borders already, e.g., some of the natural=wetland object come to my mind as an example. I quickly browsed through the related pages and discussions, for some strange reason the fuzzy border issue seems to not have been raised there at all? I suppose it's currently left solely to mappers discretion where to put the the edges. -- i. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Mon, Oct 27, 2014 at 11:33 AM, Ilpo Järvinen ilpo.jarvi...@helsinki.fi wrote: Besides, we really need to deal with object that have fuzzy borders already, e.g., some of the natural=wetland object come to my mind as an example. I quickly browsed through the related pages and discussions, for some strange reason the fuzzy border issue seems to not have been raised there at all? I suppose it's currently left solely to mappers discretion where to put the the edges. It has been discussed in the context of the Alps, The Black Forest, etc. see [1] regards m [1] https://lists.openstreetmap.org/pipermail/tagging/2013-October/015224.html ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Monday 27 October 2014, moltonel 3x Combo wrote: If you think about it a bit and do not try to place the node where you would place the label (which depends on the map projection anyway) properly placing a node for a bay is usually quite simple. The most difficult are long, fjord-like bays where a way along them would be more appropriate. I'm really curious what your method to figure out the bay area from the node is, because even as a human I find that most bay nodes can lead to many different interpretations. There are a lot of different possibilities to approach this. A very simple method would be: - find the point on the coastline closest to the bay node. - collect all coastline segments within 2-3 times the distance of the closest node. - connect all open ends of these coastlines with the closest other open end. - assemble a polygon and use it. This extremely simple approach will probably result in reasonable polygons for label placement in more than half the cases. You can easily improve the algorithm of course to properly deal with various special cases, in particular the case of small islands within a bay deserves consideration. Some coastline ways would belong to more relations, so what ? They already usually belong to 3-4 administrative boundary relations, Yes - and boundary relations are well known to be constantly broken and a pain to maintain even for experienced mappers. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Mon, 27 Oct 2014, Marc Gemis wrote: On Mon, Oct 27, 2014 at 11:33 AM, Ilpo Järvinen ilpo.jarvi...@helsinki.fi wrote: Besides, we really need to deal with object that have fuzzy borders already, e.g., some of the natural=wetland object come to my mind as an example. I quickly browsed through the related pages and discussions, for some strange reason the fuzzy border issue seems to not have been raised there at all? I suppose it's currently left solely to mappers discretion where to put the the edges. It has been discussed in the context of the Alps, The Black Forest, etc. see [1] regards m [1] https://lists.openstreetmap.org/pipermail/tagging/2013-October/015224.h tml There certainly are discussions, I also found some proposal from 2009. But my point was that this discussion not in the context of an approved tag that typically has somewhat fuzzy borders. Why it's not a problem that would be worth to mention with wetlands but suddently a major issue with bays, I really don't know. It makes very little sense to me given how much easier the fuzzy part is to isolate from bays than from wetlands with a fully autonomous algorithm. -- i.___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Mon, Oct 27, 2014 at 10:44:01AM +0100, moltonel 3x Combo wrote: On 26/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: I don't see what information is missing and cannot be easily determined automatically with a properly placed node that is contained in an area - except for the outer edge of course, which is usually ill-defined though as you said yourself. If you think about it a bit and do not try to place the node where you would place the label (which depends on the map projection anyway) properly placing a node for a bay is usually quite simple. The most difficult are long, fjord-like bays where a way along them would be more appropriate. I'm really curious what your method to figure out the bay area from the node is, because even as a human I find that most bay nodes can lead to many different interpretations. you don't. Al that the node says is somewhere there is a bay called XXX A computer algorythm would probably get it wrong most of the time. Think back to the bays within bays situation. How far along the coast do this bay extend ? Are those two nearby nodes separate bays or overlapping ones ? Most of the time there is very little agreement or hard data about the extents and hierarchy of bay naming. Sources from different countries will make different subdivisions. Great fun with multipolygons and even with perfect tagging and computer algorithm we get approximate results at best. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Mon, Oct 27, 2014 at 12:33:48PM +0200, Ilpo Järvinen wrote: On Sun, 26 Oct 2014, Christoph Hormann wrote: On Sunday 26 October 2014, Mateusz Konieczny wrote: Furthermore the outer edge of a bay, i.e. the edge that is not coastline is usually not well defined and would require an arbitrary cutoff. Yes, cutoff is unfortunately quite arbitrary. But node placement is completely arbitrary - and lacks important information. I don't see what information is missing and cannot be easily determined automatically with a properly placed node that is contained in an area - except for the outer edge of course, which is usually ill-defined though as you said yourself. Any data consumer could quite easily, if not trivially, detect that fuzzy edge in this case if it cares about it in the first place (I've have some trouble in figuring out a sensible use case in which it would make a difference to know where the fuzzy border of a bays is). Besides, we really need to deal with object that have fuzzy borders already, e.g., some of the natural=wetland object come to my mind as an example. I quickly browsed through the related pages and discussions, for some strange reason the fuzzy border issue seems to not have been raised there at all? I suppose it's currently left solely to mappers discretion where to put the the edges. http://wiki.openstreetmap.org/wiki/Proposed_features/Fuzzy http://wiki.openstreetmap.org/wiki/List_of_proposals_regarding_landuse,_geology,_geography_and_vegetation (my early draft for the purpose of getting some overview over similar issues) Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-27 12:16 GMT+01:00 Richard Z. ricoz@gmail.com: Besides, we really need to deal with object that have fuzzy borders already, e.g., some of the natural=wetland object come to my mind as an example. I quickly browsed through the related pages and discussions, for some strange reason the fuzzy border issue seems to not have been raised there at all? I suppose it's currently left solely to mappers discretion where to put the the edges. http://wiki.openstreetmap.org/wiki/Proposed_features/Fuzzy I don't like this proposal. IMHO we do indeed need a way to map fuzzy stuff, but it shouldn't be done by drawing an unfuzzy way (or node or polygon) and then declare by tags that it is not to be taken literally, i.e. that there is no such way in reality but just a fuzzy border somewhere near that way. Rather we should tackle this on the datatype (or relation) level and invent some fuzzy objects that are already fuzzy in the way they are mapped (e.g. a group of nodes (or other objects) that define an area by saying I'm inside and maybe I'm outside, so that dataconsumers could calculate an approximation for this area for their needs). cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 27/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: On Monday 27 October 2014, moltonel 3x Combo wrote: I'm really curious what your method to figure out the bay area from the node is, because even as a human I find that most bay nodes can lead to many different interpretations. There are a lot of different possibilities to approach this. A very simple method would be: - find the point on the coastline closest to the bay node. - collect all coastline segments within 2-3 times the distance of the closest node. - connect all open ends of these coastlines with the closest other open end. - assemble a polygon and use it. This extremely simple approach will probably result in reasonable polygons for label placement in more than half the cases. You can easily improve the algorithm of course to properly deal with various special cases, in particular the case of small islands within a bay deserves consideration. That's a very fragile algorythm. It depends on the mapper placing the node at a strategic point. And it has problem with long thin bays for example. You might start to see mappers tune the node position to match your algorythm. And then you'll tune your algorythm, breaking the mapper's tuning. It's quirky and might be expensive to run. Having an algorythm to turn nodes into areas is not a bad thing, since we currently have many more bay nodes than areas in the db. But it's a fallback at best. And until you get something working reasonably well upstreamed in all data consumers, we mappers should bite the bullet and map bays as areas (in other words, not treat them any different than any other area-like obbjects in osm). ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 27/10/2014, Richard Z. ricoz@gmail.com wrote: On Mon, Oct 27, 2014 at 10:44:01AM +0100, moltonel 3x Combo wrote: I'm really curious what your method to figure out the bay area from the node is, because even as a human I find that most bay nodes can lead to many different interpretations. you don't. Al that the node says is somewhere there is a bay called XXX I was asking a rhetorical question, really ;) Most of the time there is very little agreement or hard data about the extents and hierarchy of bay naming. Sources from different countries will make different subdivisions. Great fun with multipolygons and even with perfect tagging and computer algorithm we get approximate results at best. Yes, that's the main problem with bay mapping, and probably contributes to the fact that we have so many bays mapped as nodes, because mappers themselves don't know the extent of the bay (good luck, algorythm ! :p). But we regularly map approximate features, nothing new here. And I'll always prefer a source=guesswork polygon over a node automatically turned into an area using computer-mediated guesswork from a developer that didn't see the area. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Monday 27 October 2014, moltonel 3x Combo wrote: This extremely simple approach will probably result in reasonable polygons for label placement in more than half the cases. You can easily improve the algorithm of course to properly deal with various special cases, in particular the case of small islands within a bay deserves consideration. That's a very fragile algorythm. Have you tried it? On the contrary - due to its simplicity it is a very robust algorithm, it will hardly ever generate something completely wrong and fail gracefully in difficult cases. And as said it is strait away to extend this approach to specifically take care of cases where it does not work so well. [...] And until you get something working reasonably well upstreamed in all data consumers, we mappers should bite the bullet and map bays as areas No, that is not how OSM works. The mappers can choose a method to map they deem appropriate - which in this case quite clearly is nodes (less than 0.5 percent ways and relations according to taginfo). If you want to get the mappers to change their mapping you need to convince them that it is better to do so and just making it easier for those rendering maps is not a convincing argument, even in cases where unlike here there is no additional work involved. Of course by not rendering bays mapped as nodes in the standard style you could 'encourage' mappers to change their approach. This however would be mapping for the renderer which is generally frowned upon. I can't help but notice that in the whole discussion here no argument has been put formward indicating a practical advantage of bays mapped as polygons other than the ease of rendering labels. (in other words, not treat them any different than any other area-like obbjects in osm). You mean like place=town, place=city etc? SCNR. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-27 16:24 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: No, that is not how OSM works. The mappers can choose a method to map they deem appropriate - which in this case quite clearly is nodes (less than 0.5 percent ways and relations according to taginfo). the same holds true for countries, there are 0% mapped as ways, and only 7 are relations (who knows which kind of), they are all mapped as nodes: http://taginfo.openstreetmap.org/tags/place=country is a node the best representation for a country? Surely it is the easiest to map. Shall we encourage this kind of tagging? IMHO it is completely broken, but it is OK to render a label. If all you want to know about bays is where to best put a label then nodes are a good way to do it. cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 27/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: On Monday 27 October 2014, moltonel 3x Combo wrote: This extremely simple approach will probably result in reasonable polygons for label placement in more than half the cases. You can easily improve the algorithm of course to properly deal with various special cases, in particular the case of small islands within a bay deserves consideration. That's a very fragile algorythm. Have you tried it? On the contrary - due to its simplicity it is a very robust algorithm, it will hardly ever generate something completely wrong and fail gracefully in difficult cases. And as said it is strait away to extend this approach to specifically take care of cases where it does not work so well. Since AFAIK it's not implemented anywhere yet (?), neither of us has tried it. And I guess we have different thresholds as to what constitudes completely wrong. I'd be happy to be proved wrong on all accounts. [...] And until you get something working reasonably well upstreamed in all data consumers, we mappers should bite the bullet and map bays as areas No, that is not how OSM works. The mappers can choose a method to map they deem appropriate - which in this case quite clearly is nodes (less than 0.5 percent ways and relations according to taginfo). If you want to get the mappers to change their mapping you need to convince them that it is better to do so That's what this thread is about : convincing mappers that a particular way of mapping bays is better. It seems we agree on the process, if not (yet) on the result. I wouldn't read too much into the current node/way statistics: they can either be a sign of imports, or simply of approximate mapping that hasn't been refined yet (which is the norm in OSM). and just making it easier for those rendering maps is not a convincing argument, even in cases where unlike here there is no additional work involved. Of course by not rendering bays mapped as nodes in the standard style you could 'encourage' mappers to change their approach. This however would be mapping for the renderer which is generally frowned upon. I can't help but notice that in the whole discussion here no argument has been put formward indicating a practical advantage of bays mapped as polygons other than the ease of rendering labels. I really don't care that much about rendering. If that was the main concern, adding some kind of importance tag to the bay nodes would be better. And implementing your algorythm for the renderer, while quirky, would probably yield very similar rendering results to the mapping-as-polygon method, with no mapper effort. I actually care about mapping correctness. A bay is not a point in space, it's an area. Mapping it as such makes deciding which ones to render at low zoom easyer, but that's just a bonus. (in other words, not treat them any different than any other area-like obbjects in osm). You mean like place=town, place=city etc? Yes, and like everything that can be mapped as a polygon: amenity=hospital, leisure=pitch, natural=wood, etc etc etc. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-27 16:24 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: I can't help but notice that in the whole discussion here no argument has been put formward indicating a practical advantage of bays mapped as polygons other than the ease of rendering labels. Reverse geocoding. A boat comes to a bay, captain looks on a screen, and it says You are in Guantanamo Bay. So with your suggestion either the application is going to need a preprocessed database, or it will have to make it's own fuzzy logic. If it's so easy to make that logic, why don't you make a little script, and we can try it out on our examples. If it works in 95% of cases, maybe that's the best solution. We can map the rest 5% with polygons. Making it easy for the mapper is certainly a worthwhile cause. Janko ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Monday 27 October 2014, Janko Mihelić wrote: I can't help but notice that in the whole discussion here no argument has been put formward indicating a practical advantage of bays mapped as polygons other than the ease of rendering labels. Reverse geocoding. A boat comes to a bay, captain looks on a screen, and it says You are in Guantanamo Bay. But this is exactly what does not work with a hand mapped polygon either since the edge of the bay is not well defined. It seems to me the desire to have bays mapped as polygons here stems from the desire to apply such simple concepts as 'you are either inside or outside the bay'. But reality is more complex than that. Mapping them as polygons would be nothing but cargo cult towards this aim. A node tagged natural=bay means: the water around here, up to the coast around and out to open water for a similar distance, maybe somewhat further, is a bay and is named ... This is a much more accurate description of reality than a polygon. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Monday 27 October 2014, moltonel 3x Combo wrote: Have you tried it? On the contrary - due to its simplicity it is a very robust algorithm, it will hardly ever generate something completely wrong and fail gracefully in difficult cases. And as said it is strait away to extend this approach to specifically take care of cases where it does not work so well. Since AFAIK it's not implemented anywhere yet (?), neither of us has tried it. And I guess we have different thresholds as to what constitudes completely wrong. I'd be happy to be proved wrong on all accounts. Since for label rendering you don't really need a polygon there is little point in actually generating it in the first place. But i have implemented and used techniques not unlike the algorithm described for rendering bay and strait labels, like in http://maps.imagico.de/#map=3/80.707/55.862lang=enl=darkr=fjui=0 The funny thing is the first thing i do for this is reduce all features mapped as polygons to a node since the polygon is useless, its outer limit is arbitrary and the sides defined by the coastline do not match the generalized coastline used to render the map. (in other words, not treat them any different than any other area-like obbjects in osm). You mean like place=town, place=city etc? Yes, and like everything that can be mapped as a polygon: amenity=hospital, leisure=pitch, natural=wood, etc etc etc. as well as highway=*, waterway=*, natural=tree... -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On 27/10/2014, Christoph Hormann chris_horm...@gmx.de wrote: On Monday 27 October 2014, Janko Mihelić wrote: Reverse geocoding. A boat comes to a bay, captain looks on a screen, and it says You are in Guantanamo Bay. But this is exactly what does not work with a hand mapped polygon either since the edge of the bay is not well defined. It seems to me the desire to have bays mapped as polygons here stems from the desire to apply such simple concepts as 'you are either inside or outside the bay'. But reality is more complex than that. Mapping them as polygons would be nothing but cargo cult towards this aim. A node tagged natural=bay means: the water around here, up to the coast around and out to open water for a similar distance, maybe somewhat further, is a bay and is named ... This is a much more accurate description of reality than a polygon. How can a description that is definitely-inaccurate (nodes) fit reallity better than a description that is probably inaccurate ? If your aim is to make it clear that the map is as inaccurate as reallity, ok. But : * even if osm data is inaccurate, it's better for all data consumers to interpret that data in the same way, and make the same mistakes. Mapping bays as nodes add implementation-uncertainty on top of data-uncertainty. * there are surely cases where the accuracy is very good. But I still wouldn't trust an implementation to guess the area from a node. As a mapper I can control the osm data, not the heuristics that consumers implement. * even though nothing is standardized, there are ways to tag that a geometry is fuzzy/inaccurate. Nobody is forcing you to switch to polygons today. Go ahead and keep using nodes if you feel it's enough; it actually is for many usecases. But don't think that nodes describe reallity better. And let people upgrade nodes to areas if they're willing to do the work. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
2014-10-27 17:37 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: But this is exactly what does not work with a hand mapped polygon either since the edge of the bay is not well defined. it will work in most cases, and only give questionable information when you are close to the fuzzy end towards the open sea (or another bay). In these cases there won't be a correct answer from a human either, because it simply isn't clear where that border is. It seems to me the desire to have bays mapped as polygons here stems from the desire to apply such simple concepts as 'you are either inside or outside the bay'. yes, but even more: how big is this bay (compared to others), are there bays inside bays etc. (hierarchy, nesting) cheers, Martin ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Mon, 27 Oct 2014, Martin Koppenhoefer wrote: 2014-10-27 17:37 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: But this is exactly what does not work with a hand mapped polygon either since the edge of the bay is not well defined. it will work in most cases, and only give questionable information when you are close to the fuzzy end towards the open sea (or another bay). In these cases there won't be a correct answer from a human either, because it simply isn't clear where that border is. IMHO, the most controversial thing in this all is that the approach Christoph is proposing would require us to not map natural=bay but natural=bay_entry instead, and that is obviously exactly where the fuzzy part is. That is, a mapper would be forced to place bay nodes into the place where nobody can say for sure if it's in the bay or not. Otherwise his algorithm would obviously end up failing because of arbitary picked threshold that makes lots of assumptions about the shape of the bay. The main assumptions are about width of the bay and depth at the nearest coastline that is not in the either extreme of the bay. Consider e.g. a very wide bay which has two pockets but at the middle you have some penisula extending towards the bay entry and thus also towards the bay node. But it would certainly work in many cases just fine like most of the algorithms tend to do (of course, assuming we'd map bay_entry instead of bay). -- i. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
When working near the coast of Maine in the US, I see lots of bays. In most cases, the ultimate source data for the bay names seems to be various government maps and databases: GNIS, ancient nautical charts, or whatever. There's a high degree of agreement between sources: If an island has 4 unnamed coves and 1 named cove in GNIS, then I'll usually find the exact same data on the nautical charts. But the key point here is that none of these official sources represent bays as polygons. GNIS uses a pointssomewhere in the bay. The nautical charts print the name somewhere in the middle of the bay. Effectively, the official data really is a point, plus whatever guesswork a human reader supplies. The rendering on openstreetmap.org is pretty good: it just prints the bay name at the marked point, and shows it across a reasonable range of scales. There are some weird cases with nested bays, but those are weird on the nautical charts, too. Merging all of these thousands of official bay points into the surrounding coastal polygons sounds like an editing nightmare. And the data wouldn't be better—the underlying official sources are all points, anyway. 2014-10-27 16:04 GMT-04:00 Ilpo Järvinen ilpo.jarvi...@helsinki.fi: On Mon, 27 Oct 2014, Martin Koppenhoefer wrote: 2014-10-27 17:37 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: But this is exactly what does not work with a hand mapped polygon either since the edge of the bay is not well defined. it will work in most cases, and only give questionable information when you are close to the fuzzy end towards the open sea (or another bay). In these cases there won't be a correct answer from a human either, because it simply isn't clear where that border is. IMHO, the most controversial thing in this all is that the approach Christoph is proposing would require us to not map natural=bay but natural=bay_entry instead, and that is obviously exactly where the fuzzy part is. That is, a mapper would be forced to place bay nodes into the place where nobody can say for sure if it's in the bay or not. Otherwise his algorithm would obviously end up failing because of arbitary picked threshold that makes lots of assumptions about the shape of the bay. The main assumptions are about width of the bay and depth at the nearest coastline that is not in the either extreme of the bay. Consider e.g. a very wide bay which has two pockets but at the middle you have some penisula extending towards the bay entry and thus also towards the bay node. But it would certainly work in many cases just fine like most of the algorithms tend to do (of course, assuming we'd map bay_entry instead of bay). -- i. ___ 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] natural=bay as nodes are evil
On Monday 27 October 2014, Ilpo Järvinen wrote: IMHO, the most controversial thing in this all is that the approach Christoph is proposing would require us to not map natural=bay but natural=bay_entry instead, and that is obviously exactly where the fuzzy part is. That is, a mapper would be forced to place bay nodes into the place where nobody can say for sure if it's in the bay or not. Then you have misunderstood me - i am not suggesting any change to the current mapping practice (including the option to map as a polygon when deemed appropriate by the mapper). If you want to formulate a formal mathematical rule for where the node for a bay is best placed: Place it so the variance of the distance of the node to the bay's shores is minimized. Most existing nodes comply with this rule remarkably well. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
Dana 27. 10. 2014. 21:30 osoba Eric Kidd emk.li...@randomhacks.net napisala je: The rendering onopenstreetmap.orgis pretty good: it just prints the bay name at the marked point, and shows it across a reasonable range of scales. There are some weird cases with nested bays, but those are weird on the nautical charts, too. Why would we adopt mapping styles from nautical charts if they have weird renderings with some bays? We have to be better then those charts, even though they are official. Dana 27. 10. 2014. 21:42 osoba Christoph Hormann chris_horm...@gmx.de napisala je: If you want to formulate a formal mathematical rule for where the node for a bay is best placed: Place it so the variance of the distance of the node to the bay's shores is minimized. Most existing nodes comply with this rule remarkably well. What's the best place for the node in Guantanamo Bay? Is the current node well placed? http://www.openstreetmap.org/node/2501579651 Janko ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Sunday 26 October 2014, Mateusz Konieczny wrote: Please, try mapping bays as areas - not as nodes. It is really rare to see it done this way - but it is doable, see http://overpass-turbo.eu/s/5CQ Doable for sure but an awfully bad idea, mapping bays as areas would mean two features for the same object (coastline polygon and bay area). Furthermore the outer edge of a bay, i.e. the edge that is not coastline is usually not well defined and would require an arbitrary cutoff. Maintaining bay polygons would be an awful mess, they would end up frequently being broken. And there is no gain at all in terms of substantial information in the database compared to nodes (since the coastline is already mapped and the non-coastline edge is arbitrary). The reason you would prefer areas is probably simply that this would make it easier for to use in rendering - but making life more difficult for the mapper just to make it easier for the renderer is not a good idea. Based on the coastlines and the bay nodes you can quite easily generate approximate bay polygons that can be used for the purpose of labeling for example (yes, even for the Paulsdorfer Bucht). This argument by the way was already made in a slightly different context in https://github.com/gravitystorm/openstreetmap-carto/issues/804 -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
Doable for sure but an awfully bad idea, mapping bays as areas would mean two features for the same object (coastline polygon and bay area). Coastline polygon and bay area is not the same object. Yes, part of border is shared - it is nothing wrong. Also it is possible to use for example multipolygons. Furthermore the outer edge of a bay, i.e. the edge that is not coastline is usually not well defined and would require an arbitrary cutoff. Yes, cutoff is unfortunately quite arbitrary. But node placement is completely arbitrary - and lacks important information. 2014-10-26 19:00 GMT+01:00 Christoph Hormann chris_horm...@gmx.de: On Sunday 26 October 2014, Mateusz Konieczny wrote: Please, try mapping bays as areas - not as nodes. It is really rare to see it done this way - but it is doable, see http://overpass-turbo.eu/s/5CQ Doable for sure but an awfully bad idea, mapping bays as areas would mean two features for the same object (coastline polygon and bay area). Furthermore the outer edge of a bay, i.e. the edge that is not coastline is usually not well defined and would require an arbitrary cutoff. Maintaining bay polygons would be an awful mess, they would end up frequently being broken. And there is no gain at all in terms of substantial information in the database compared to nodes (since the coastline is already mapped and the non-coastline edge is arbitrary). The reason you would prefer areas is probably simply that this would make it easier for to use in rendering - but making life more difficult for the mapper just to make it easier for the renderer is not a good idea. Based on the coastlines and the bay nodes you can quite easily generate approximate bay polygons that can be used for the purpose of labeling for example (yes, even for the Paulsdorfer Bucht). This argument by the way was already made in a slightly different context in https://github.com/gravitystorm/openstreetmap-carto/issues/804 -- Christoph Hormann http://www.imagico.de/ ___ 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] natural=bay as nodes are evil
On Sunday 26 October 2014, Mateusz Konieczny wrote: Furthermore the outer edge of a bay, i.e. the edge that is not coastline is usually not well defined and would require an arbitrary cutoff. Yes, cutoff is unfortunately quite arbitrary. But node placement is completely arbitrary - and lacks important information. I don't see what information is missing and cannot be easily determined automatically with a properly placed node that is contained in an area - except for the outer edge of course, which is usually ill-defined though as you said yourself. If you think about it a bit and do not try to place the node where you would place the label (which depends on the map projection anyway) properly placing a node for a bay is usually quite simple. The most difficult are long, fjord-like bays where a way along them would be more appropriate. Specific arguments aside - i am not sure if you realize the consequences it would have if subareas of oceans would generally be mapped as polygons - large bays usually contain smaller bays and are parts of a sea and there might be a strait between an island and the coast within that bay. If you want to edit the coastline in such situation you would end up having to deal with a handful of convoluted multipolygon relations, some of them of colossal size. Properly editing coastlines is difficult for beginners in the first place. This would make it borderline impossible. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] natural=bay as nodes are evil
On Sun, Oct 26, 2014 at 05:12:20PM +0100, Mateusz Konieczny wrote: Please, try mapping bays as areas - not as nodes. It is really rare to see it done this way - but it is doable, see http://overpass-turbo.eu/s/5CQ not practical in most cases. Almost every bay is part of a larger bay and so forth. The borders and hierarchy are very arbitrary. The nodes, as much as they suck give a quite realistic picture of this fuzzy state. Richard ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
