[Qgis-user] Styling polygon borders: preventing double rendering between polygons

[Jorge Gustavo Rocha]

Hi Chris,

I've asked the question simple as possible, but I'm really trying to
accomplish the use cases you mentioned!

I'm trying to symbolize all different administrative levels, including
the shoreline. This can be partially accomplish with lines by stacking
all, from the most general ones, like the international border, to the
the less ones. Less important borders are covered by more important
ones, like in the simple screenshot:
https://nextcloud.geomaster.pt/index.php/s/Pb3XWNCtzqbPQyi

This does not solve the shoreline problem. And, if we use markers, we
can not cover the border underneath. We really need to render just the
most general border on that segment.

We are using just "simple features" to represent the world. This simple
representation is quite limited for this kind of relations between
layers. We need more semantics.

Thanks you for your input, Chris!

Regards,

Jorge

On 11/06/20 16:03, chris hermansen wrote:
> Jorge and List,
>
> On Thu, Jun 11, 2020 at 7:13 AM Jorge Gustavo Rocha <jgr at geomaster.pt
> <mailto:jgr at geomaster.pt>> wrote:
>
>     Thank you for the feedback, Karl and Christoph.
>
>     Your work around is valid. It is possible to transform the
>     polygons into lines and then render them correctly.
>
>     It would be nice to have an option to render only once adjacent
>     polygons, with a a common border.
>
>
> In my experience, this is one of many kinds of "cartographic  boundary
> weirdness" that would be nice to have, conceptually speaking anyway.
>
> Another is an international boundary that disappears when the ocean is
> on one side and land is on the other (the border between Spain and
> Portugal symbolized as an international border, but Portugal's and
> Spain's coastlines symbolized as shoreline).
>
> Or provincial / state boundaries disappear when one country is on one
> side and one is on the other (the border between Portalegre and Castel
> Branco shows as provincial border, but the border between Portalegre
> and Extremadura shows as national border).
>
> And of course as you say, in no case should the border be symbolized
> twice.
>
> Regardless of whether the process of this symbolization is manual or
> automatic, there is obviously a process of converting polygons to
> lines, removal of duplicate lines, then analyzing the entities to the
> left and right to determine how to symbolize the line according to
> some pre-configured list of priorities.
>
> -- 
> Chris Hermansen · clhermansen "at" gmail "dot" com
>
> C'est ma façon de parler.
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