Styling with GeoNode (Basics)

This section introduces the concepts of the Styled Layer Descriptor (SLD) markup language.

SLD is the styling engine used by the GIS backend (i.e. GeoServer). It allows us to create beautiful and informative portrayals out of raw geospatial data.

In this section, you will also use the CSS extension module that allows you to build map styles using a compact, expressive styling language already well known to most web developers: Cascading Style Sheets. The standard CSS language has been extended to allow for map filtering and managing all the details of producing a map.

The examples will have styles in SLD and CSS languages.

WARNING: CSS styling is only supported by GeoServer, which is the default GIS backend provided with GeoNode. In the official GeoServer Styling documentation, you can find useful references, such as the SLD Cookbook and the CSS Cookbook.

Uploading and Replacing the Dataset Default Style

This procedure allows us to quickly update and replace the current dataset default style with a new one from the hard disk.

WARNING: This procedure currently only works with SLD files

Before using the style, we will need to slightly modify it to match the correct field names of the Mainrd dataset.
Go to the Mainrd dataset detail page;
Click on 1.the system File Browser, navigate to 2./opt/data/sample_data/user_data
- RIGHT-CLICK with the mouse on the file named foss4g_mainrd.sld
- Select and click 3.Open with Other Application
Click on the View all applications button and then select Text Editor and change the 1.label_name to uppercase LABEL_NAME, click 2.Save, and 3.close
Go to the Mainrd dataset detail page; click on 1.Edit -> 2.Upload Style
From the Style Upload page, click on the Choose files button and navigate to 1./opt/data/sample_data/user_data. Select the file 2.foss4g_mainrd.sld and then click on 3.Open
Click on Upload file and, once finished, on Return to Dataset

WARNING: If the page does not refresh correctly, click together CTRL-SHIFT-CANC and clear the browser image cache from the last hour
Go back to the dataset detail page and refresh the page. Notice how the Legend has changed, as has the styling of the dataset. Try zooming in, you will notice some labels appearing.
Go ahead and update the Thumbnail by clicking on the Edit -> Edit Info. You can then update it in two ways: 1: click on the upload icon on the current thumbnail and upload an image from your device. 2: click on the map icon and adjust the map to the desired dimensions.
Once the thumbnail has been saved
Go back to the datasets list and verify it has been updated

Adding more Base Datasets and Styles

Boulder City Limits

From the location /opt/data/sample_data/pretty_maps/data/boulder upload the dataset BoulderCityLimits
From the location /opt/data/sample_data/pretty_maps/styles upload the style foss4g_citylimits.sld
The dataset and legend should appear as shown here
Set the thumbnail as we have done previously

Buildings

From the location /opt/data/sample_data/pretty_maps/data/boulder upload the dataset Buildings050714
WARNING: pay attention to only select the files shown in the figure below, do not include the .sld and .xml ones
From the location /opt/data/sample_data/pretty_maps/styles upload the style foss4g_buildings.sld
Notice that the Legend presents 3 different symbols, also notice that no feature will be visible unless you zoom very close to the buildings

By taking a closer look at the style source code, we can see that:

We have a set of Rule elements, each one constrained by some ScaleDenominator limits.
The Shadow rule also defines a Displacement making the polygons translate on the X-Y dataset

<?xml version="1.0" encoding="UTF-8"?>
  <sld:StyledLayerDescriptor xmlns="http://www.opengis.net/sld" xmlns:sld="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" version="1.0.0">
    <sld:UserLayer>
      <sld:LayerFeatureConstraints>
        <sld:FeatureTypeConstraint/>
      </sld:LayerFeatureConstraints>
      <sld:UserStyle>
        <sld:Name>Buildings050714</sld:Name>
        <sld:Title/>
        <sld:IsDefault>1</sld:IsDefault>
        <sld:FeatureTypeStyle>
          <sld:Rule>
            <sld:Name>Shadow</sld:Name>
            <sld:MinScaleDenominator>5000.0</sld:MinScaleDenominator>
            <sld:MaxScaleDenominator>15000.0</sld:MaxScaleDenominator>
            <sld:PolygonSymbolizer>
              <sld:Geometry>
                <ogc:Function name="offset">
                  <ogc:PropertyName>the_geom</ogc:PropertyName>
                  <ogc:Literal>6.0</ogc:Literal>
                  <ogc:Literal>-6.0</ogc:Literal>
                </ogc:Function>
              </sld:Geometry>
              <sld:Fill/>
            </sld:PolygonSymbolizer>
          </sld:Rule>
        </sld:FeatureTypeStyle>
        <sld:FeatureTypeStyle>
          <sld:Rule>
            <sld:Name>Label</sld:Name>
            <sld:MaxScaleDenominator>10000.0</sld:MaxScaleDenominator>
            <sld:PolygonSymbolizer>
              <sld:Fill>
                <sld:CssParameter name="fill">#FF0000</sld:CssParameter>
              </sld:Fill>
            </sld:PolygonSymbolizer>
            <sld:TextSymbolizer>
              <sld:Label>
                <ogc:PropertyName>LABEL_NAME</ogc:PropertyName>
              </sld:Label>
              <sld:Font>
                <sld:CssParameter name="font-family">Arial</sld:CssParameter>
                <sld:CssParameter name="font-size">12.0</sld:CssParameter>
                <sld:CssParameter name="font-style">normal</sld:CssParameter>
                <sld:CssParameter name="font-weight">normal</sld:CssParameter>
              </sld:Font>
              <sld:LabelPlacement>
                <sld:PointPlacement>
                  <sld:AnchorPoint>
                    <sld:AnchorPointX>
                      <ogc:Literal>0.5</ogc:Literal>
                    </sld:AnchorPointX>
                    <sld:AnchorPointY>
                      <ogc:Literal>0.5</ogc:Literal>
                    </sld:AnchorPointY>
                  </sld:AnchorPoint>
                  <sld:Displacement>
                    <sld:DisplacementX>
                      <ogc:Literal>0.0</ogc:Literal>
                    </sld:DisplacementX>
                    <sld:DisplacementY>
                      <ogc:Literal>0.0</ogc:Literal>
                    </sld:DisplacementY>
                  </sld:Displacement>
                  <sld:Rotation>
                    <ogc:Literal>0.0</ogc:Literal>
                  </sld:Rotation>
                </sld:PointPlacement>
              </sld:LabelPlacement>
              <sld:Halo>
                <sld:Radius>
                  <ogc:Literal>2</ogc:Literal>
                </sld:Radius>
                <sld:Fill>
                  <sld:CssParameter name="fill">#FFFFFF</sld:CssParameter>
                </sld:Fill>
              </sld:Halo>
              <sld:Fill>
                <sld:CssParameter name="fill">#000000</sld:CssParameter>
              </sld:Fill>
              <sld:VendorOption name="autoWrap">100</sld:VendorOption>
              <sld:VendorOption name="maxDisplacement">50</sld:VendorOption>
            </sld:TextSymbolizer>
          </sld:Rule>
          <sld:Rule>
            <sld:Name>fill</sld:Name>
            <sld:MaxScaleDenominator>25000.0</sld:MaxScaleDenominator>
            <sld:PolygonSymbolizer>
              <sld:Fill>
                <sld:CssParameter name="fill">#B3B3B3</sld:CssParameter>
              </sld:Fill>
            </sld:PolygonSymbolizer>
          </sld:Rule>
        </sld:FeatureTypeStyle>
      </sld:UserStyle>
    </sld:UserLayer>
  </sld:StyledLayerDescriptor>

Set the thumbnail as we have done previously

Parcels

From the location /opt/data/sample_data/pretty_maps/data/boulder upload the dataset Parcels
From the location /opt/data/sample_data/pretty_maps/styles upload the style foss4g_parcels.sld. The dataset only appears at very high levels of zoom
Set the thumbnail as we have done previously

Pointlm

From the location /opt/data/sample_data/pretty_maps/data/boulder upload the dataset pointlm
From the location /opt/data/sample_data/pretty_maps/styles upload the style foss4g_point_landmark_ds_ns.sld

At a first glance, the dataset will appear as a set of grey square points. Let’s take a closer look at the SLD definition

<?xml version="1.0" encoding="UTF-8"?>
   <sld:StyledLayerDescriptor
   xmlns="http://www.opengis.net/sld"
   xmlns:sld="http://www.opengis.net/sld"
   xmlns:ogc="http://www.opengis.net/ogc"
   xmlns:gml="http://www.opengis.net/gml"
   xmlns:xlink="http://www.w3.org/1999/xlink" version="1.0.0">

     <sld:UserLayer>
       <sld:LayerFeatureConstraints>
         <sld:FeatureTypeConstraint/>
       </sld:LayerFeatureConstraints>
       <sld:UserStyle>
         <sld:Name>tl 2010 08013 pointlm</sld:Name>
         <sld:Title/>
         <sld:FeatureTypeStyle>
           <sld:Rule>
             <sld:Name>landmarks</sld:Name>
             <ogc:Filter>
                 <ogc:PropertyIsGreaterThan>
                   <ogc:Function name="strLength">
                     <ogc:PropertyName>IMAGE</ogc:PropertyName>
                   </ogc:Function>
                   <ogc:Literal>0</ogc:Literal>
                 </ogc:PropertyIsGreaterThan>
             </ogc:Filter>
             <sld:PointSymbolizer>
               <sld:Graphic>
                 <sld:ExternalGraphic>
                   <sld:OnlineResource xlink:type="simple" xlink:href="./img/landmarks/${IMAGE}" />
                   <sld:Format>image/png</sld:Format>
                 </sld:ExternalGraphic>
               </sld:Graphic>
               <VendorOption name="labelObstacle">true</VendorOption>
             </sld:PointSymbolizer>
             <sld:TextSymbolizer>
               <sld:Label>
                 <ogc:PropertyName>FULLNAME</ogc:PropertyName>
               </sld:Label>
               <sld:Font>
                 <sld:CssParameter name="font-family">Arial</sld:CssParameter>
                 <sld:CssParameter name="font-size">12.0</sld:CssParameter>
                 <sld:CssParameter name="font-style">normal</sld:CssParameter>
                 <sld:CssParameter name="font-weight">normal</sld:CssParameter>
               </sld:Font>
               <sld:LabelPlacement>
                 <sld:PointPlacement>
                   <sld:AnchorPoint>
                     <sld:AnchorPointX>
                       <ogc:Literal>0.5</ogc:Literal>
                     </sld:AnchorPointX>
                     <sld:AnchorPointY>
                       <ogc:Literal>1.0</ogc:Literal>
                     </sld:AnchorPointY>
                   </sld:AnchorPoint>
                   <sld:Displacement>
                     <sld:DisplacementX>
                       <ogc:Literal>0.0</ogc:Literal>
                     </sld:DisplacementX>
                     <sld:DisplacementY>
                       <ogc:Literal>-14.0</ogc:Literal>
                     </sld:DisplacementY>
                   </sld:Displacement>
                   <sld:Rotation>
                     <ogc:Literal>0.0</ogc:Literal>
                   </sld:Rotation>
                 </sld:PointPlacement>
               </sld:LabelPlacement>
               <sld:Halo>
                 <sld:Radius>
                   <ogc:Literal>1.5</ogc:Literal>
                 </sld:Radius>
                 <sld:Fill>
                   <sld:CssParameter name="fill">#FFFFFF</sld:CssParameter>
                 </sld:Fill>
               </sld:Halo>
               <sld:Fill>
                 <sld:CssParameter name="fill">#000033</sld:CssParameter>
               </sld:Fill>
               <sld:Priority>200000</sld:Priority>
               <sld:VendorOption name="autoWrap">100</sld:VendorOption>
             </sld:TextSymbolizer>
           </sld:Rule>
         </sld:FeatureTypeStyle>
       </sld:UserStyle>
     </sld:UserLayer>
   </sld:StyledLayerDescriptor>

We can see the notation xlink:href="./img/landmarks/${IMAGE}", this is a GeoServer extension allowing us to read some values from the source dataset attributes and then use them to dynamically render the SLD.

In that specific case, GeoServer looks for some filenames according to the ${IMAGE} attribute value in a relative folder named ./img/landmarks/.

To correctly render this style, we will need to copy this folder, containing the correctly named images, into the GeoServer styles folder.

We will also have to give that folder the correct permissions to allow GeoServer to access it.

The first step is to copy the img folder into the correct GeoServer styles one
- Open a system file browser window and go to 1./opt/data/sample_data/pretty_maps/styles
- RIGHT-CLICK on the 2.img folder
- Select 3.Copy from the side menu
From the system file browser window go to /opt/data/geoserver_data/workspaces/geonode/, it will probably ask for ROOT permissions. Just insert the password geonode every time it asks for one
Go to the styles folder inside the GeoNode workspace and hit CTRL+V, this will copy the img folder into the new location
RIGHT-CLICK on the newly created 2.img folder and click on the 3.Properties link of the context menu
Assign the permissions to the others group as shown in the figure below
Refresh the dataset page, you should be able to see the icons appearing on the map preview
Set the thumbnail as we have done previously

Remaining Boulders datasets

From the location /opt/data/sample_data/pretty_maps/data/boulder upload the datasets:
- srtm_boulder
- Streets
- Trails
- Wetlands_regulatory_area
From the location /opt/data/sample_data/pretty_maps/styles upload the styles:
- foss4g_dem2.sld to srtm_boulder
- foss4g_streets.sld to Streets
- foss4g_trails.sld to Trails
- foss4g_wetlands.sld to Wetlands_regulatory_area