1.5. Miscellaneous Tools

1.5.1. Compute Distances and Area

The Compute Distance and Area tool uses a Java applet that will substitute the current map image. This GeometryEditor applet will let you draw several kind of geometries (points, linestrings and polygons) while displaying the distance and area (if applicable) of the currently drawn geometry. To call the applet, please click on the icon. Once the applet is loaded, the map part of the GeoViewer provides additional tools, as illustrated below:

The following functionalities are available in the applet:

• always displays the current geometry perimeter and area.

• is a movable toolbar that contains only the M button that cycles through the three geometry mode: point set, linestring and polygon.

• designates the currently drawn geometry. You can add or move points using the left mouse button and remove a point with right-click.

Simply use any other GeoWidget tool to quit the applet.

1.5.2. Annotations

Annotations are shareable features describing a given place. An annotation feature consists of a geometry, a name and a description. Annotations are logically grouped into containers called folders. A new annotation can only be created within an existing folder. Annotations act as a regular layer within the context, you can thus toggle their visibility through the LayerVisibility widget. Managing annotations in the GeoViewer can be achieved through two different widgets:

• The ManageAnnotations widget allows you to create and delete folders and to edit or delete existing annotations. This widget is accessible by clicking on . The following screenshot shows the widget displaying a folder/annotation tree structure:

  Figure 1-17. Manage Annotations

  

  If you click on an annotation folder name, the folder then acts as the current folder, meaning newly created annotations will belong to this folder.

• The CreateAnnotation () widget allows you to create a new annotation on the current map and within the current folder. When this widget is called, a popup appears and the map display switches to the GeometryEditor applet. Use this popup to enter both a name and a description for your annotation, draw the annotation geometry on the map using the applet explained above and then click Submit. Note that the pop-up displays the name of the current annotation folder, as shown below:

  Figure 1-18. Create an Annotation

  

1.5.3. Get Information about Features

The GeoViewer provides a GetFeatureInfo widget compliant with the OpenGIS Web Map Service specification. If your context contains queryable layers, then you can select one of these layers to act as the active layer, meaning that subsequent calls of the GetFeatureInfo widget will query features from the active layer. The result of a GetFeatureInfo operation is often an HTML document produced by a server-side rendering rule.

In order to use the GetFeatureInfo widget, you first have to define an active layer to query using the ManageLayer widget. The active layer is designated by a target icon and can be changed by clicking on layer names, as shown below:

Once a queryable layer is set, you can click the GetFeatureInfo icon . Note that this tool behaves like the Zoom or Pan tools, meaning it stays selected until another tool is chosen. Just click near the features you want to obtain information on and the result will be displayed in a pop-up window, as shown below:

The GeoViewer assumed that the GetFeatureInfo call on the server returns an HTML document.

1.5.4. Changing the current SRS

You can change the context's current spatial reference by clicking this icon and then enter the new SRS code as an EPSG Id. Please refer to the European Petrol Survey Group website for more information on EPSG codes.

Applying a non-appropriate SRS obviously causes an error in the client.

1.5.5. Change the Image Size

You can resize the map part of the GeoViewer by clicking this icon and then enter the new map size in pixels. Note that the map size is kept into the XML context file.