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Is it possible to change the symbology of a WMS from external developers?

I am harvesting WMS and the symbology is very messy and unclear when some are viewed together.

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  • Yes, you can send a GetMap request with your own SLD, defining your own style.
    – nmtoken
    Jan 15, 2017 at 16:56
  • @nmtoken - OK, show me how! Here's a group of WMS layers I'd like to modify the fill color of: Name: MODIS fire detections URL: fsapps.nwcg.gov/afm/cgi-bin/mapserv.exe?map=conus.map& If you can show me / us / the Internet how an SLD could be applied to any of these layers, I'd be eternally grateful.
    – grego
    Sep 18, 2020 at 20:13
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    @grego if you want an example of applying an SLD to a service (in an openlayers client) go to portal.onegeology.org/OnegeologyGlobal manually select the FIN GTK 1:1M MINERAL OCCURRENCES (ERML-LITE PORTRAYAL) layer, use the analysis functionality, apply your style, get a resymbolized map and save the SLD
    – nmtoken
    Sep 22, 2020 at 6:45

2 Answers 2

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Not always. Changes can be limited for adjusting the "symbology" because a basic WMS provides a pre-styled map.

There are sometimes controls/options you can use in the GetMap request to control transparency and such - but nothing to actually change the style (outline/line thickness, fill and outline colour, etc...) of the layers as those are built on the server side.

Sometimes you can also add each WMS layer individually. This helps because you can re-order them to draw how you like.

That's the one major restriction of a basic WMS - You will forever be at the mercy of the cartographer. A WFS on the other hand lets you access the raw vector data for your own styling purposes but is not always an option.

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  • This might be true for a basic WMS, but most WMS support SLD. With SLD you can send a style to the WMS.
    – nmtoken
    Jan 15, 2017 at 16:54
  • @nmtoken Yup, I seen that in lele3p's answer and was gdal to learn about this (see comment there) =)
    – SaultDon
    Jan 18, 2017 at 17:33
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There are ways to send an SLD file with the WMS request to ask the server to style the map in a way that suits you. However not all servers (or clients) support this as it is much less efficient (it prevents the server caching the result for other users for example).
See these examples:

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