[GIS] Dynamic SLD styling based on min / max value in a PostGIS column

cql-filtergeoserverpostgissld

I have a PostGIS table that contains the GDP of countries together with their polygon boundaries. I am using GeoServer to display this data via OpenLayers.

When styling the data, I want to avoid having to hardcode numeric range / colour pairs in my SLD file.

Is it possible to create an SLD style file that dynamically determines the minimum and maximum value of GDP that are present in a PostGIS column, for example through CQL, and then uses that information to colour the map?

Best Answer

Following Dynamic SLD styling - unique colours for linestrings I would suggest adding a "color value" column to your postGIS table is the easiest solution. The column should always be updated with respect to the current range of GDP values. Then, you might access it in your SLD with a PropertyValue in the CssParameter tag.

Related Solutions

GeoServer 2.2 – How to Style Mixed Geometry Types Effectively

The first validation error is because you are missing Name, Title, Abstract, NamedLayer and UserLayer elements in your SLD. The second validation error refers to the missing filter element inside your Rule element. So if you add the filter element and the standard elements in the sld elemet your SLD should validate fine. Finally our SLD should look like this:

<?xml version="1.0" encoding="ISO-8859-1"?>
<StyledLayerDescriptor version="1.0.0" 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"
  xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd">
  <NamedLayer>
    <Name></Name>
    <UserStyle>
      <Title></Title>
      <Abstract></Abstract>
      <FeatureTypeStyle>
        <Rule>
            <ogc:Filter>        
                <ogc:PropertyIsEqualTo>
                    <ogc:Function name="geometryType">
                        <ogc:PropertyName>the_geom</ogc:PropertyName>
                    </ogc:Function>
                    <ogc:Literal>Polygon</ogc:Literal>
                </ogc:PropertyIsEqualTo>
            </ogc:Filter>    
            <PolygonSymbolizer>
            <Stroke>
                <CssParameter name="stroke">#0000ff</CssParameter>
                <CssParameter name="stroke-width">1</CssParameter>
            </Stroke>
            </PolygonSymbolizer>
        </Rule>
      </FeatureTypeStyle>
    </UserStyle>
  </NamedLayer>
</StyledLayerDescriptor>

If you want to style other geometrytypes - just create a new rule with the symbolizer and geometrytype filter you want to style.

UPDATE

Your point rule should have a PointSymbolizer element instead of the PolygonSymbolizer. So your point rule look like this:

 <Rule>
        <ogc:Filter>        
            <ogc:PropertyIsEqualTo>
                <ogc:Function name="geometryType">
                    <ogc:PropertyName>the_geom</ogc:PropertyName>
                </ogc:Function>
                <ogc:Literal>Point</ogc:Literal>
            </ogc:PropertyIsEqualTo>
        </ogc:Filter>    
        <PointSymbolizer>
        <Graphic>
              <Mark>
                <WellKnownName>circle</WellKnownName>
                <Stroke>
                  <CssParameter name="stroke">#0000ff</CssParameter>
                  <CssParameter name="stroke-width">2</CssParameter>
                </Stroke>
              </Mark>
              <Size>6</Size>
            </Graphic>
        </PointSymbolizer>
    </Rule>

See more on how to style points in the GeoServer SLD Cookbook

[GIS] CssParameter stroke-width min max value Geoserver

The css values are in pixels so you probably won't see much change with fractional values. Try using 0 as I think GeoServer handles that as a special case.

Further information on SLD can be found at http://docs.geoserver.org/stable/en/user/styling/sld-cookbook/lines.html

Best Answer

Related Solutions

GeoServer 2.2 – How to Style Mixed Geometry Types Effectively

[GIS] CssParameter stroke-width min max value Geoserver

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