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]
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