[Tagging] Using multipolygons to map bays in Alaska

Kevin Kenny kevin.b.kenny at gmail.com
Thu Nov 15 16:35:55 UTC 2018

On Thu, Nov 15, 2018 at 10:03 AM Frederik Ramm <frederik at remote.org> wrote:

> > Long story short:  My suggestion is and has always been to map bays with
> > nodes in those cases where this - together with the coastline -
> > perfectly documents the verifiable information available on the
> > geometry of the bay.
> Agree on the node idea, but it would have to include some size signifier
> (and I think someone recently tried to add a "sqm" tag to water body
> nodes for that purpose which I also criticised...). I don't think you
> are recommending a relation that includes the actual coastline and the
> label node, but if you do then I am against that because I don't want
> every coastline to be part of 10 relations in the end.
Using point features alone defeats any attempt to do more sophisticated
label shaping than current Mapnik is capable of rendering.

Using coarse labeling polygons replaces the problem of having a shoreline
participate in multiple relations with the problem of having multiple
inaccurate representations of the same shoreline all running approximately
parallel. I can't see how that's any easier to manage. Moreover, it defeats
any sort of analysis that depends on adjacency. "The shoreline of the Gulf
of Bothnia" becomes a meaningless idea in that data model - it's just
another part of the coastline of Europe, with no reliable way of
identifying that Oulu is on that particular shoreline while Helsinki and
Tallinn are not. (I intentionally choose cases where ambiguity about the
mouth of the bay is not relevant.)

If the relation includes the actual boundaries (while having to be somewhat
arbitrary about indefinite ones), there's no need for a label node. Label
nodes that have the mapper identify where to put the label on an area
feature have no purpose other than label painting. They have no existence
in the field. They are purely tagging for the renderer.

Also, once again, could I ask you to make it clear whether you're
expressing your opinion or an official position of the DWG or the OSMF? The
fact that you deleted the relation - whcih, as you observe, some mapper put
some very careful work into - suggests that you are indeed expressing an
official position.  If it is an official position, I think the community is
owed a clearer statement of what the rules are - because the introductory
material on the Wiki appears very much to diverge from how the project is
actually being run. If I'm going to contribute to the map, I need some
reasonable likelihood that all my work won't be reverted because it offends
against rules that I do not comprehend. Reading the available documentation
has offered very little enlightenment.

I know that I've placed things in the map with which you personally
disagreed vehemently. In particular, I've performed a couple of imports
that you thought were entirely unwarranted - although by the end of the
discussion, the argument that was left standing was simply the
still-controversial one that imports always have a greater negative effect
on the community than the value of the imported data. After discussions on
talk-us and imports, you had the restraint not to revert the actual
imported data. Now you appear to be taking pride in what appears (without
researching the history) to be an arbitrary revert of a mapper's attempt to
curate the data manually, in a way that appears to comport with OSM's
multipolygon model but offends you because of opening the door to having a
way be a member of too many relations. In the absence of a more formal
guideline, I'm not really sure what to think, and wonder what among the
objects that I've mapped might be at risk.
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