GeoServer raster with external SLD

Question

I want to use an external SLD (hosted in my server) for symbolizing a raster in GeoServer.

The SLD below works if used as default style in GeoServer. If I copy it (changing some colors) and put outside GeoServer, save as SLD (or XML), and call the GetMap with SLD=https://my_server/mySLD.sld the map I get is still with the 'default, Geoserver' style

<StyledLayerDescriptor version="1.0.0" 
xsi:schemaLocation="http://www.opengis.net/sld StyledLayerDescriptor.xsd" 
xmlns="http://www.opengis.net/sld" 
xmlns:ogc="http://www.opengis.net/ogc" 
xmlns:xlink="http://www.w3.org/1999/xlink" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:se="http://www.opengis.net/se">
  <NamedLayer>
    <Name>my_schema:my_layer</Name>
    <UserStyle>
      <FeatureTypeStyle>
               <Rule>
                    <RasterSymbolizer>
                        <Geometry>
                           <PropertyName>GRAY_INDEX</PropertyName>
                        </Geometry>
                        <Opacity>1</Opacity>
                        <ColorMap>
                           <ColorMapEntry color="#E69800" label="1" opacity="0.0" quantity="0.0"/>                     
                            <ColorMapEntry color="#1b4bde" label="Building" opacity="1.0" quantity="1.0"/>
                            <ColorMapEntry color="#bcbcbc" label="Ground cover" opacity="1.0" quantity="2.0"/>
                                 
                    </ColorMap>
       </RasterSymbolizer>
      </Rule>
      </FeatureTypeStyle>
    </UserStyle>
    </NamedLayer>    
  </StyledLayerDescriptor>

shortly, WMS call would be like this (also tried withou STYLES param) https://my_geoserver_url/wms?service=WMS&version=1.1.0&request=GetMap&layers=my_schema:my_layer&STYLES=&SLD=https://my_server/my_sld.sld&transparent=true&bbox=...&format=image/png

I did this for dynamic filtering in vector data and all good (SLDs are created dynamically via PHP), so I am wondering if the problem is that with RASTER data is not possible

Answer 1

When the style is used in GeoServer, it gets stripped of everything but the first UserStyle/NamedStyle, and that part is used to render the layer, blindly (that's not conforming to standard, but also the behavior GeoServer had for the past 15-20 years, everyone relies on it).

When using a remote style instead, you get the full standard compliant treatment instead. Long story short, your Style must have a NamedLayer matching your layer name and must be marked as the default style. See the library mode documentation for more details