I am considering an edit involving "natural=coastline" involving the Great Lakes that are shared between the US and Canada. This has been discussed on the Talk-US and Talk-Ca lists and there have been no objections to date.
Background: Lake Superior is represented both with individual ways tagged "natural=coastline" (although not all islands have their ways tagged "natural=coastline"), as well as *two* multipolygon relations tagged "natural=water" (this tag has been removed from the one relation already) with some islands members having a role of "inner." The first (for the purpose of the discussion) relation seems to include the entire outline of the lake, but not all of the islands, particularly on the Canadian side. The second includes only the outline of the lake on the Canadian side, and the part of the border between the US and Canada that runs through the lake. It appears that this second relation does include all, or nearly all, of the islands on the Canadian side. Representing the lake and its islands in these multiple manners seems to cause rendering issues. Proposed Course of action. 1) Download Canadian Lake Superior relation and all its members to JOSM. 2) Make sure every individual member way is tagged "natural=coastline" (except the way(s) that form the boundary between Canada and the US. 3) Make sure every individual way has land on the left. (except the US Canadian border that runs through the lake). 4) Remove "natural=water" from the Canadian relation 5) Upload. Later 6) Make sure all members of the Canadian relation appear in the overall relation (or that their purpose is filled my some other member(s) of the overall relation. 7) Delete the Canadian relation. Comments are welcome. Technical advice is welcome, e.g. how to easily find island ways that go clockwise (water on the left) Mike (user: tekim) On Sun, May 10, 2015 at 9:51 AM, Christoph Hormann <chris_horm...@gmx.de> wrote: > On Sunday 10 May 2015, Jochen Topf wrote: > > Hi! > > > > For about 10 days the coastline has been broken and no updates have > > been going through. This is largely due to some broken mapping in > > North America where coastlines overlap and some features have been > > tagged both as coastline and waterways, which doesn't make any sense > > at all. > > Note overlaps between waterway=riverbank areas and the coastline are > generally not an issue and are also not really that uncommon (classic > and long term case for that it the Elbe in northern Germany) - they of > course complicate things a bit and can be misleading for mappers. > > > Please, everybody: If you are doing something with the coastlines, > > take extra care. Coastlines are fragile, have special taggging rules > > unlike anything else in OSM and if you break them in only one place, > > chances are coastlines updates for the whole world will stop! > > Indeed. And if you have a complex coastline situation like when you > need to add or remove the coastline tag to/from a larger water area and > have not done something like this before just leave the coastline > mapping as it is and add a fixme tag indicating what should be changed > and place a note asking for help doing that. > > -- > Christoph Hormann > http://www.imagico.de/ > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk >
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