Style with scalar and vector field

[marceloandrioni]

Hello, I am trying to create a new style based on this example from the EDAL User Guide. Basically a scalar field (ssh) with a vector field (current direction) over.

To test the setup first I created one style for the ssh (style_ssh.xml) and one style for the current (style_uv.xml). Restarted Tomcat and the new styles were correctly recognized as shown in the images below.

I then joined the styles in a single file (style_sshuv.xml) and tested on the SLD Parser Test Tool. The Parser Test showed exactly the image I expected:

<?xml version="1.0" encoding="ISO-8859-1"?>
<StyledLayerDescriptor version="1.1.0" xsi:schemaLocation="http://www.opengis.net/sld
StyledLayerDescriptor.xsd" xmlns="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc"
xmlns:se="http://www.opengis.net/se" xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:resc="http://www.resc.reading.ac.uk">
  <NamedLayer>
    <se:Name>remo_hycom124_2d/ssh</se:Name>
    <UserStyle>
      <se:Name>Red-blue palette showing SSH</se:Name>
      <se:CoverageStyle>
        <se:Rule>
          <se:RasterSymbolizer>
            <se:Opacity>1.0</se:Opacity>
            <se:ColorMap>
              <resc:Segment>
                <se:LookupValue>Rasterdata</se:LookupValue>
                <resc:BelowMinValue>extend</resc:BelowMinValue>
                <resc:ValueList>
                  <se:Name>div-BuRd2</se:Name>
                </resc:ValueList>
                <resc:AboveMaxValue>extend</resc:AboveMaxValue>
                <resc:Range>
                  <resc:Minimum>-1.0</resc:Minimum>
                  <resc:Maximum>1.0</resc:Maximum>
                  <resc:Spacing>linear</resc:Spacing>
                </resc:Range>
                <resc:NumberOfSegments>250</resc:NumberOfSegments>
              </resc:Segment>
            </se:ColorMap>
          </se:RasterSymbolizer>
        </se:Rule>
      </se:CoverageStyle>
    </UserStyle>
  </NamedLayer>
  <NamedLayer>
    <se:Name>remo_hycom124_2d/u:v-dir</se:Name>
    <UserStyle>
      <se:Name>Arrows showing current direction</se:Name>
      <se:CoverageStyle>
        <se:Rule>
          <resc:ArrowSymbolizer>
            <se:Opacity>1.0</se:Opacity>
            <resc:ArrowSize>8</resc:ArrowSize>
            <resc:ArrowColour>#FF000000</resc:ArrowColour>
            <resc:ArrowBackground>transparent</resc:ArrowBackground>
            <resc:ArrowStyle>FAT_ARROW</resc:ArrowStyle>
          </resc:ArrowSymbolizer>
        </se:Rule>
      </se:CoverageStyle>
    </UserStyle>
  </NamedLayer>
</StyledLayerDescriptor>

I restarted Tomcat again but the new style doesn't appear in the drop-down list in the ssh or u:v-dir variables. Do someone has faced a similar problem and was able to solve it?

An example of the kind of file I am trying to visualize can be found here.

On a side note, assuming I manage to see the new style, I was also wondering if ncWMS/edal XML specification has a variable to represent just the name of the dataset and not the full name of the variable ($layerName is equal to dataset_name/variable_name). I am asking this because I have several datasets (multiple hydrodynamic models output) that share the same structure, that is, all have variables named ssh, u and v. With a variable representing just the name of the dataset I could write a single style that would work for all these datasets, e.g.:

...
  <NamedLayer>
    <se:Name>$datasetName/ssh</se:Name>
    <UserStyle>
   ...
    </UserStyle>
  </NamedLayer>
  <NamedLayer>
    <se:Name>$datasetName/u:v-dir</se:Name>
    <UserStyle>
   ...
    </UserStyle>
  </NamedLayer>

System:
ncWMS v2.4.1
Apache Tomcat/8.5.45
Linux x86_64 Kernel 4.15.0-58-generic

[guygriffiths]

The reason the style is not appearing in the dropdown for either the ssh or the u:v-dir variables is because neither of those variables is sufficient for your style, it has to be the combination of the two. There is a feature in the latest snapshot version of ncWMS which allows variables to be logically grouped, so that they have a parent variable which would support this style. However, I think that this will cause issues with the fact that u:v-dir is already a "virtual" variable, and not something in the data. For now I think you will need to just specify the style manually in the GetMap URL, or use a third-party WMS viewer.

There is currently no way of referencing a general dataset in a style template.

I am not currently in a position to work on ncWMS, but I will leave this issue open, so that if I get some time I can have a look into it.

[marceloandrioni]

Ok, too bad is not currently possible to do that in Godiva3. I think that despite all the support to use the ncWMS in other GIS applications most people still use Godiva3 for the easily available options of selecting time and height/depth dimensions, auto-color limits, etc, considering these extra WMS features are not implemented in ArcView or QGIS (or any plugin that I know of).

Thank you.