1.3. Managing Layers
Layer management involves: discover and add layers from OpenGIS/ISO web services, browse layers metadata, remove or hide layers and reorder the layers within the current context.
1.3.1. Add Layers
You can add geographic layers exposed by WMS, WCS and WFS services to the current context. These services are further called providers into this guide since they provide data, either bitmap or vector-based.
You can add new layers in two different ways:
Using the AddProvider widget if you know the URL of the service.
Using the DiscoverLayer widget if you want to add layers discovered in an OpenGIS Catalog (CS-W) service.
1.3.1.1. Using AddProvider
You have to use the AddProvider widget, accessible through
, in order to add layers from
OpenGIS/ISO WMS/WCS/WFS services to your context.
Please enter the service URL, choose WMS, WFS or WCS from the drop-down list, then click on the button. The widget will then present a list of the layers exported by the service. Choose one or many layer(s) to add then click to add the selected layer(s) to your map. You can then use the Fit to Layer widget to quickly view the new layer(s).
The GeoViewer provides a default portrayal for WFS-based layers so you will be able to directly visualize vector-based data. Please contact your administrator if you want to replace this default portrayal by a custom one.
Adding coverage layers exposed by a WCS service requires the use of a remote Coverage Portray Server (CPS) in order to have a visible result on the map. Please follow this procedure to add a coverage to the map:
Use the AddProvider widget to enter the Web Coverage Server URL. You will see in the next section that you can also discover WCS in an OpenGIS Catalog. Once you have entered the WCS URL and selected the layers as for WMS and WFS, these layers will be added to the context. As opposed to WMS/WFS layers, these layers are NOT directly visible on the map since coverages need first to be portrayed by a Coverage Portray Server (aka CPS). The next steps will thus consist in configuring the coverage portrayal.
Use the ManageLayer widget to configure the coverage layer. As shown in the screenshot below, there is a CONFIG hyperlink beside our newly added layer.
Click the CONFIG link to jump to the next step.
The following screenshot presents the CPS configuration panel. The parameters entered in this widget populate an SLD (Styled Layer Descriptor) that will be sent to the CPS of your choice. The result will be a visible layer that renders our coverage.
The parameters are, from top to bottom (please refer to the CPS specifications for more information on the parameters semantic):
Cloud Coverage: You can set both a min and max value that will be used as filter in getCoverage requests.
Red/Green/Blue channels: You can use the three drop-down lists to map the RGB channels to the different coverage bands.
Contrast enhancement: Choose between Normalize, None and Histogram.
Dates range: You can set a dates range that will be used as a filter in GetCoverage requests.
Color Map: Instead of mapping bands to RGB channels, you may use a color map produced in the IONIC StyleEditor. Click the button to select the color map XML file then .
CPS URL: You need to enter a Coverage Portray Server URL in this field.
The ManageLayer widget is often used in the GeoViewer to perform some configuration on layers. It is the case for WCS/CPS layers but also for the GetFeatureInfo widget.
We can now use the FitToLayer widget to quickly navigate to our brand new layer:
1.3.1.2. Discovering Layers in a Catalog
The GeoViewer allows you to query an OpenGIS Catalog service (aka CS-W) in order to retrieve
layers you can add to your map. Please use this icon 
to call the discovery widget.
You can now enter your search criteria. Up to four criteria can be used to search for layers but they are all optional, meaning you can just hit the button and get back the catalog whole content. The criteria you can use are, from top to bottom of the widget:
A geographic box: You can use the box selector beside the mini-map to draw a region that covers the area on which you want to retrieve layers.
A keyword that will be used to search within the services capabilities and metadata. Note that you can use the % wildcard to replace a sequence of characters.
Type: You can restrict your search to either WMS, WFS or WCS.
An ISO 19115 Category. Note that you can select multiple categories using Ctrl-click.
The following screenshot presents the result of a query for WMS on America:
You can now add layers to your context by clicking their name. Hoovering the layer name with the cursor allows you to view the underlying service URL. You may now use the Fit To Layer widget to quickly navigate to newly added layers.
 | Visit IONIC AskTheSpider website to learn more about OpenGIS Catalog services. |
1.3.2. Browsing Layers Metadata
You can view the ISO 19115 Metadata associated to each layer, if any, by using the
ShowMetadata widget accessible through 
.
While the widget is displayed, choose a layer name from the left area and use the 5 tabs to
browse metadata categories, as shown in the following screenshot:
1.3.3. Remove Layers
Use the 
icon to display the
RemoveLayer widget. Select the layer(s) you want to remove from your context as usually then
click the button.
| Don't remove the Gazetteer and Annotations layers from the context, rather toggle their visibility since it is impossible to add them from the GeoViewer user interface. |
icon.
icon to call this
widget. Usage is the same as for the other