Re: [Tagging] Verifiability of geometry
On Tue, 18 Jun 2019 at 02:13, Warin <61sundow...@gmail.com> wrote: > > For the 'centre' of place I tend tot go either for the post office or the > railway station. > I have a vague memory, which a brief search with google is unable to confirm, that milestones in Britain gave their distance from the head post office of a town. Even if that vague memory is correct, I know of one town (Lampeter/Llanbedr Pont Steffan) where a rent increase forced the main (only) post office to move from the centre of town to a supermarket on the outskirts of the town. Railway station? Lampeter had one once but it, too, was on the then outskirts of the town. Cardigan had one once, but it was on the then outskirts of the town. In fact, whilst larger towns/cities in the UK may have a main (or only) railway station in a central location, the smaller towns tend to have railway stations closer to the outskirts. Or even outside the outskirts. Somewhere along the thoroughfare known as High Street or Main Street might be a better bet. But towns can be drastically redeveloped over time and what was once the main street is no longer deserving of the name it retains. -- Paul ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Verifiability of geometry
On 17/06/19 23:53, marc marc wrote: Le 17.06.19 à 03:53, Joseph Eisenberg a écrit : since this is where everyone can agree is in Paris. Paris maybe, but you are talking about Ile-de-France. where the single node representing "ile de france" should be located ? look at the history of the node, you will see that there is no unanimous opinion, it ends up being positioned where it is most attractive, it is totally arbitrary Yes these things can be subjective. They can depend on human emotion not a physical thing. For the 'centre' of place I tend tot go either for the post office or the railway station. But it depends on the place and the local thinking. Locals know the place so they are don't say 'meet you in Paris' they would talk about a far more localised thing. It is the tourist or causal observer who talks of 'Paris' as though it were a specific locality . and on there scale of though it is. They are not concerned with the actual accuracy of the nodes placement .. as long as it is within Paris they will be happy. Message: don't be too worried about the precise 'centre' of some large thing.. the actual users are not worried about it. ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Verifiability of geometry
Le 17.06.19 à 03:53, Joseph Eisenberg a écrit : > we don't label Paris as the geographic center of Ile-de-France. You confuse the two the Paris label is actually not based on the geography of Ile de France since these are 2 unrelated things except that one is admin_center of the other > Instead, we place the node near the center of the main > business district and historic centre of the city of Paris, this way of doing things is common, but I find it inconsistent. one cannot both say that the label role is arbitrary and replace it with a node whose placement follows a conflict between several unwritten and subjective rules. it would be much more objectifiable to create nodes for the different criteria (historical/economic/administrative/tourism/geodesic centre), possible member of their relation, and each datause could choose its main criterion when these locations are not the same > since this is where everyone can agree is in Paris. Paris maybe, but you are talking about Ile-de-France. where the single node representing "ile de france" should be located ? look at the history of the node, you will see that there is no unanimous opinion, it ends up being positioned where it is most attractive, it is totally arbitrary ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Verifiability of geometry
On Sunday 16 June 2019, Daniel Koc4� wrote: > > To have interpretation is not a logical error and I didn't claim > that. But lack of objective support makes it just your opinion. It > would be really bad if you would contradict yourself, but still it's > just a weak point worth showing. OpenStreetMap is fundamentally based on the existence of a single, verifiable reality. The truthfulness of a statement in that reality is not a matter of majority opinion but a question if it can be demonstrated to be true or false. > Your strait definition for example does not contain logically > fallacy, but is just unrelated to reality, as I have shown, which is > still OK for philosophy, but bad for mapping, which is about actually > representing the world outside. I think this is exactly disadvantage > for the project. You have shown nothing w.r.t. my statement about straits with what you wrote. This can be easily shown through you not being able to verifiably state the length of the straits i am talking about. What is the length of the Bering Strait for example? > I have shown you a positive proposition of proper solving the problem > of the example object. You have not shown that is logically wrong, so > I guess it should enough for you, if you follow your own rules of > proving, so here you lack some consistency. > > But what worries me more is that you just not even commented why this > would be a bad thing for reasons other than logic. I am sorry but we can't really have a productive discussion here if you keep ignoring past discussions and their results. The statement that i have not commented on why your ideas for how OSM should work are bad is preposterous. Both Joseph and me have explained in detail on github why the status quo in rendering is a bad idea and has no long term future. I have discussed the fundamental concept of verifiability at length on my blog: http://blog.imagico.de/verifiability-and-the-wikipediarization-of-openstreetmap/ and in discussions on the wiki, in diary entries and on mailing lists. > For some reason you claim that changing the type of geometry in the > world of geometry into another type of geometry is OK. I wonder if > you would change the name into some other name in the database? You seem to have a fundamental misunderstanding here - with the choice of how something is modeled in the OSM database mappers do not make a statement about the geographic reality and this is therefore not subject to verifiability. The geometry itself (the coordinates of the nodes and how they are arranged in ways and relations) however is. And i agree with Joseph that this is not the best place for such discussion. Given the abstract nature of the topic and how it concerns the very foundations of the project i would even say mailing lists with spontaneous comments and a natural tendency for tunnel vision on the current discussion thread are not really a good medium to handle this kind of topic. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Verifiability of geometry
Daniel, I find this whole conversation pretty off-topic for the tagging forum. Perhaps "Talk" would be more appropriate, since you closed the original discussion on github. 1)Simplification of geometries: > There can be some simplification used (just beware of oversimplification, > especially for bigger objects), but this is always worse than lack of > simplification. Have you every tried to edit an object that was imported badly, with thousands of nodes a few meters apart? I have edited riverbanks that were probably imported by a low-quality automated process, and roads directly imported from GPS traces, and they were very hard to fix (in retrospect I should have just deleted them and redrawn from the new imagery...). That's why the "Fast drawing mode" in JOSM always simplifies objects. Too many unnecessary nodes is worse than too few. It's easy to add nodes to a rough sketch. Removing badly drawn nodes is quite hard. Database objects in OpenStreetMap are abstract representations of map features, not precise copies of a satellite raster image. 2) Straits between curved coastlines: >> straits between concave coasts are one dimensional entities, they have a >> width but they have no length. > I see no support for this claim, so I completely don't agree with it: The example is something like a wide strait between two small, thin islands. Here the strait is just the point at the middle of the channel between the two. You can't make a reasonable line or area out of it, because both islands come to a sharp point, aimed at the strait: https://www.openstreetmap.org/node/3979746373#map=13/34.2944/135.0302 3) Node location verifiability: >> the verifiability of a node location representing a feature exclusively >> depends on if multiple independent placements of the node converge to a >> single location. This is a completely scale independent problem meaning >> variance of different placements can be anywhere from less than a meter to >> hundreds of kilometers. This has no bearing on the principal verifiability. >>>This sentence is very complex, I'm not sure what do you think. Simplified: A node is verifiable if you get a bunch of different local mappers together and ask them all to place a node (or move the node to the correct location). As you add more and more nodes from more people, the average location should become more and more accurate and precise. There will always be a few outliers, but most of the dots will be close enough together. For a small object like an ATM, the nodes will probably be within a few meters of each other, and the average location should be accurate to the nearest meter or even the nearest 10 cm. For a town, the nodes for the place=town will probably be a few 10s or 100's of meters apart, but the average location will probably be within a circle of 10's of meters, since a town is much larger and less precisely defined than an ATM. For a large, vague feature like a sea, the nodes of different mappers will probably be a many kilometers apart. Since the sea is 1000s of times larger than the ATM and much less precisely defined, this is normal, and it's good enough for a computer to guess where to place a label and the size of a label on a map. 4) Gulf of Guinea >When you have 4 different limits of the Gulf of Guinea for example ( >https://commons.wikimedia.org/wiki/File:Limites_du_golfe_de_Guin%C3%A9e-fr.svg >), you will have 4 different central points which don't converge at all (the >distance between the middle of A and D is roughly 1000 km), so using nodes >does not help anything. >At best one can put it in the A area as the common part of all of them, but >this is indirectly choosing A area as proper, which is just hiding the >problem, not getting rid of it. We should choose the center of the smallest area that can be verified to be that feature. For example, we don't label Paris as the geographic center of Ile-de-France. Instead, we place the node near the center of the main business district and historic centre of the city of Paris, since this is where everyone can agree is in Paris. You don't put the node of the place=city San Francisco in the middle of the San Francisco bay, because that's the middle of the metropolitan area, or the middle of the county. You don't even put it in the middle of the land area of the city of San Francisco: you put it near the city hall and the central business district, in the northeast corner of the city on Market Street, because that's the centre of San Francisco by the smallest definition (the historic core). Continued: >The solution would be for example to ask local people from all 12 countries if >they think this part of the coastline belongs to the bay and take their claim >above what others (non-local people) say. At best, it will give you properly >sourced shape. At worst, you may not get the consistent answer - then you >might just simply not map it at all. Ok, I'm a world traveler, but I'm not going
Re: [Tagging] Verifiability of geometry
W dniu 16.06.2019 o 21:20, Christoph Hormann pisze: > You have stated disagreement with several of these statements but you > have not challenged them in any way by pointing out a logical error or > by arguing why the suggested approach how mappers should decide on how > to map things is of disadvantage to them or to the project as a whole. To have interpretation is not a logical error and I didn't claim that. But lack of objective support makes it just your opinion. It would be really bad if you would contradict yourself, but still it's just a weak point worth showing. Your strait definition for example does not contain logically fallacy, but is just unrelated to reality, as I have shown, which is still OK for philosophy, but bad for mapping, which is about actually representing the world outside. I think this is exactly disadvantage for the project. > I would suggest to you not to concentrate on your spontaneous emotional > reaction You did not see or hear me and you claim some personal statements, which are not only false, but also sound patronizing to me. Please, don't. > of dislike to views like mine that differ from your own but to > consider what objective arguments you have that support your position > and what long term consequences this would have. I have shown you a positive proposition of proper solving the problem of the example object. You have not shown that is logically wrong, so I guess it should enough for you, if you follow your own rules of proving, so here you lack some consistency. But what worries me more is that you just not even commented why this would be a bad thing for reasons other than logic. > You have made clear on a lot of occasions that you reject the concept of > verifiability as a No, I don't - it's just your interpretation. For some reason you claim that changing the type of geometry in the world of geometry into another type of geometry is OK. I wonder if you would change the name into some other name in the database? That's what I call verifiability. And I have not heard something like "verifiability is only for names and existence of the object", the verifiability of geometry was special case to make it clear. If you change the geometry in a subjective way, it does not sound like verifiable for me - you have introduced something virtual instead of real geometry. This rule does not tell anything about perceived expectations of mappers, but also nothing about perceived problems with maintenance. We have areas for admin boundaries and coastlines, which are a burden, but for the sake of verifiability we don't turn them into nodes for example, out of the blue. Even if they are huge and it means fixing them if they break. -- "I see dead people" [Sixth Sense] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
Re: [Tagging] Verifiability of geometry
On Sunday 16 June 2019, Daniel Koc4� wrote: > > Christoph (imagico) has proposed there a set of example rules that he > believes are self evident and invited to challenge them if someone > disagrees, so here I am: Not quite - this is just a collection of statements regarding matters where you claim i did not provide answers to or where you repeatedly bring up arguments based on assumptions that have been refuted in the past already (like the persistent idea that any two-dimensional entity should best be modeled in OSM with a polygon). It is neither meant to be an exhaustive framework of principles nor are they necessarily useful as practical rules. All of these are not new statements - they are not literal quotes but i have made them in previous discussions in similar form (here, on the wiki, on github or elsewhere). You have stated disagreement with several of these statements but you have not challenged them in any way by pointing out a logical error or by arguing why the suggested approach how mappers should decide on how to map things is of disadvantage to them or to the project as a whole. With challenging my statements i mean providing evidence for them to be false. I would suggest to you not to concentrate on your spontaneous emotional reaction of dislike to views like mine that differ from your own but to consider what objective arguments you have that support your position and what long term consequences this would have. You have made clear on a lot of occasions that you reject the concept of verifiability as a guiding principle for mapping decisions but so far the only reason for this you have ever given is essentially because it is inconvenient and it prevents the addition of data to OSM you would like to see added. Given that the reasons why we have and should keep the verifiability principle have been discussed really extensively this all seems frankly a bit opportunistic. -- Christoph Hormann http://www.imagico.de/ ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
[Tagging] Verifiability of geometry
Hi, There are still some problems with verifiability of objects geometry. This has been discussed lately here: https://github.com/gravitystorm/openstreetmap-carto/pull/3750 but we came to the conclusion that this is not the best place to go with fundamental problems, so I come here to talk about tagging strategies. Christoph (imagico) has proposed there a set of example rules that he believes are self evident and invited to challenge them if someone disagrees, so here I am: * polygons are a way to geometrically define a two dimensional entity through (and only through) an explicit delineation of its one dimensional boundaries. I agree with that. That's why area mapping for bays is good as long as you have a source for this. This is what we do with admin borders - we get the nodes that we know and simply link them. Or we use some data from authorities. No matter what source do you use, there can be disagreement (look at admin borders problems which are not solved to this moment, yet we don't simplify admin objects into nodes or lines because of that). * for the decision what kind of feature to use to represent a certain real world feature in the OSM database mappers should put mapping and data maintenance efficiency above perceived desires of data users. The main criterion should be how to most efficiently represent verifiable information on the feature in question without storing either redundant or non-verifiable data. Written rule does not support this interpretation, it's short and clear. Data maintenace is not a rule, is not mentioned there even as an excuse or exception and of course is not higher level rule than verifiability. On the other hand people commonly use nodes or lines for representing areas. There is simply a clash between written rules and the common usage. It's the open question how should it be solved. * there is no principal connection between the nature of a real world object and how it can or should be represented in OSM above the mapping efficiency criterion previously mentioned. I don't agree here. There can be some simplification used (just beware of oversimplification, especially for bigger objects), but this is always worse than lack of simplification. * straits between concave coasts are one dimensional entities, they have a width but they have no length. I see no support for this claim, so I completely don't agree with it: - "Most commonly it is a channel of water" (Wikipedia, strait) - channel has length and width - "The shortest distance across the strait, 33.3 kilometres" (Wikipedia, Strait of Dover) - the mentioned thing is only a part of the strait, not the whole entity - "A narrow area of water surrounded by land on two sides and by water on two other sides." (description on the OSM wiki) * the verifiability of a node location representing a feature exclusively depends on if multiple independent placements of the node converge to a single location. This is a completely scale independent problem meaning variance of different placements can be anywhere from less than a meter to hundreds of kilometers. This has no bearing on the principal verifiability. This sentence is very complex, I'm not sure what do you think. When you have 4 different limits of the Gulf of Guinea for example ( https://commons.wikimedia.org/wiki/File:Limites_du_golfe_de_Guin%C3%A9e-fr.svg ), you will have 4 different central points which don't converge at all (the distance between the middle of A and D is roughly 1000 km), so using nodes does not help anything. At best one can put it in the A area as the common part of all of them, but this is indirectly choosing A area as proper, which is just hiding the problem, not getting rid of it. The solution would be for example to ask local people from all 12 countries if they think this part of the coastline belongs to the bay and take their claim above what others (non-local people) say. At best, it will give you properly sourced shape. At worst, you may not get the consistent answer - then you might just simply not map it at all. -- "I see dead people" [Sixth Sense] ___ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
