[mapserver-users] Polygon border with marker line symbol

[Rahkonen Jukka (MML)]

Hi,

I do not know of any automatic method that prevents the duplicate drawing. With simple symbology of solid, opaque lines there is no need to do anything because the result looks the same anyway. For advanced symbology a simple rendering trick with a solid, opaque background may give good result for some kind of symbology but sometimes nothing else helps but to remove the overlapping segments permanently from the data that is used for rendering the borders.

I believe that there are some examples with images about the "line with white background and symbols above that trick" in gis.stackexchange but this answer is just literal
https://gis.stackexchange.com/questions/171182/how-to-make-dashed-lines-between-adjacent-polygons-render-correctly-in-qgis

The "convert polygons into polylines and clean overlapping segments workflow"  explained with images in an ESRI blog
https://blogs.esri.com/esri/arcgis/2007/09/26/excerpt-for-dash-dot-line-entry/

The operation "polygons into polylines without overlapping segments" can be performed by creating a planar graph or the GIS software may have a special tool for that purpose like my favorite OpenJUMP. However, it is rather common that polygon shapefiles are not topologically clean and borders between adjacent polygons do not match exactly. In that case the source data must be made to match first. Usually I do that with OpenJUMP and the Adjust Polygon Boundaries tool. Fine tuning can be tedious and next update from the data provider will have the same errors so I tend to use simple styles :).

-Jukka Rahkonen-

Lähettäjä: Björn Danielsson [mailto:bjorn.danielsson at falubo.se]
Lähetetty: 12. lokakuuta 2017 13:03
Vastaanottaja: Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi<mailto:jukka.rahkonen at maanmittauslaitos.fi>>; Anton Bakker <anton.bakker at geocat.net<mailto:anton.bakker at geocat.net>>; lars.schylberg at blixtmail.se<mailto:lars.schylberg at blixtmail.se>
Kopio: mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>
Aihe: Re: [mapserver-users] Polygon border with marker line symbol

Hi,

Jukka R,
I would love to learn how to prevent polygon borders to be drawn twice.

Björn D



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