On Fri, Apr 19, 2019 at 6:28 AM Christoph Hormann <o...@imagico.de> wrote: > It is interesting that the idea that large size abstract concepts > projected onto arbitrarily delineated parts of the physical geography > by cultural convention like bays, peninsulas, linear rivers and > plateaus might not be suitable for being recorded in OSM is by several > people in this discussion reinterpreted as - and i am only slightly > exaggerating here - that mappers may only record things after they have > personally touched every centimeter of them.
The fact that as many people 'reinterpreted' your words suggests that it might behoove you to review them. In any case, we're in agreement that the Bay of Biscay, the Drake Passage or the Bight of Benin are quite problematic for arbitrariness. Something near half of their boundaries are arbitrary - worse in the case of the Drake Passage. There is some sort of problem involving these objects that would merit investigation. They are not what I'm talking about here. I've at least heard you as arguing that no OSM object ought to have an arbitrary boundary, anywhere on its perimeter. That rules out almost all waterways, most of which are connected to other waterways by rivers or straits. Of course, it rules out peninsulæ and isthmuses. I know we've had a disagreement before about the Hudson River, where your interpretation of 'coastline' unambiguously denies the river's existence for the lower 200+ km of its reach - all because the boundary between riparian, estuarine and marine environments cannot be established without drawing an arbitrary line, and the first unambiguous physical boundary for where it is unquestionably a 'river' is the Federal Dam in Troy, New York. If locals are consulted, they will place the river's mouth at the Battery on the southern tip of Manhattan Island - but somehow, in the quest to destroy all potential ambiguity, deferring to the locals in this instance is cultural imperialism. We've been through several proposals for defining the riparian/estuarine/marine border, for river mouths and complex coastlines. All have failed on a great many objects in the perception of the local mappers. Despte your radical intolerance for ambiguity, I think we do have a broad consensus among the other mappers that the locals are virtually always right. I return to the example of the Red Sea. I know of no culture that denies that it is a single named entity. It has hundreds of km of coastline, and its borders (except for the mouths of streams, which are rare in the desert surrounding it) are well defined, with two very small arbitrary borders: the entrance to the Suëz canal and the narrow straits on either side of the island of Perim (Ar: Barim: بريم). It is possible for reasonable people to disagree, perhaps, about whether the villiage of Faghal (فغال - I may be mistransliterating) is on the Red Sea or the Persian Gulf, but for hundreds of km, there is no ambiguity: nobody would disagree that Port Sudan (بور سودان) is a port on the Red Sea. Mapping the Red Sea as a single point loses that topologic and shape information. It is throwing the baby away with the bath water. Whether Faghal is or is not on the Red Sea is a question that I am happy to leave to any mapper in Faghal who is willing to offer a local judgment! To the extent to which such judgments trigger political or cultural conflicts, there will never be a good solution in OSM. If the locals are currently fighting a war over a boundary, OSM cannot resolve the question of where the boundary lies. The Black Sea, of course, offers a similar problem in construction. Tiny arbitrary lines have to be drawn across the Bosphorus, the Strait of Kerch, and some river mouths. I do not accept the idea that the Red Sea is an abstract concept without a relevant geographic feature bound to it. I do not accept that "Port Sudan is on the Red Sea, and Odessa is on the Black Sea" are not verifiable facts. The fact that the seas are joined to narrow straits across which arbitrary lines must be drawn does not negate the existence of the Red Sea, or the Black Sea. It is not just waterbodies and peninsulæ, but even administrative boundaries have this issue. I live in a state where portions of some county lines are indefinite - they are in uninhabited wilderness and have never been surveyed. Nevertheless, the definite portions of the lines are necessary, as is a consistent topology. For a point in an inhabited area, where the lines are established, one needs to be able to compute with certainty, "is this point in Franklin or Essex County?" Yes, if you choose a point in the uninhabited wilderness, the answer might be, "I don't know" or might be wrong. But nobody cares about the answer for an arbitrary point in uninhabited wilderness. A wrong answer is perfectly acceptable. (It would not be acceptable to say that the point is in Suffolk County, hundreds of km away, clearly. But to answer which of two neighbouring counties owns it is likely to require a series of surveys and a court case.) We inhabit an ambiguous world. To be intolerant of the slightest ambiguity is to throw away most of its richness. I don't support mapping the Red Sea in OSM immediately, because I am informed that the mapping of objects that large presents severe technological issues for those that manage OSM's servers and for those who consume OSM's data at scale. I respect the large-multipolygon moratorium for that reason. I've also refrained from mapping smaller objects with ambiguous borders because of the controversy of which this thread is the latest manifestation. I am expressing my opinion on the mailing list rather than in the database. For smaller objects, I'm continuing to muse about introducing linear ways, tagged something like boundary=indefinite, for completing the topology of these nearly closed objects. The sole purpose of boundary=indefinite would be to participate in a multipolygon, completing its topology, and it would flag to all data consumers that the precise positioning of that portion of the multipolygon is unknown or unknowable. I'd further state that a way tagged boundary=indefinite should have no other tagging, and must always be a way of a multipolygon. I'm willing to accept a rule of thumb such as 'no more than 10% of the perimeter of a multipolygon's outer way should be indefinite' and of course I would state that the judgment of the locals governs in deciding where to place the endpoints of an indefinite way. (I insist on being able to bend that rule of thumb to accommodate very unusual situations such as county lines across wilderness areas.) Is this a possible way out of the "all or nothing" attitude that I'm seeing here? Essentially, your position is, "if we know or can verify only 99.9% of an area feature's boundary, that's the same as if we can verify none of it." I'm taking the contrary position that "if the vast majority of an object's perimeter is known, draw an approximate line for the rest, mark it as indefinite, and at least benefit from the part that is known." _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
