Retrieving vector data and metadata

In this section we will learn how to deal with vector data using WFS. First we will learn how to deal with metadata and then how to retrieve the features. We will be using the layer named Counties in the workshop namespace.

Note

The Open Geospatial Consortium Web Feature Service Interface Standard (WFS) provides an interface allowing requests for geographical features across the web using platform-independent calls. One can think of geographical features as the “source code” behind a map, whereas the WMS interface or online mapping portals like Google Maps return only an image, which end-users cannot edit or spatially analyze.

1. Navigate to the GeoServer Welcome Page.

2. On the Welcome page locate the Layer Preview link (no need to login).

   

   Layer Preview

3. Navigate to the WFS GML output of the Counties layer.

   

   WFS GML output

   Depending on the browser, the output may be unformatted or recognized as XML. Here is what Firefox 3 shows: http://localhost:8083/geoserver/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=geosolutions:Counties&maxFeatures=50&outputFormat=GML2

   

   Default WFS layer preview.

   Note

   We recommend the Mozilla Firefox web browser for navigating WFS response documents.

4. Now that we know the quick and easy way to get WFS data, let’s go back and do it the way a standard WFS client works. First, the only thing expected to be known is the WFS server URL: http://localhost:8083/geoserver/ows?service=WFS&version=1.0.0

   Using that URL, we can issue a GetCapabilities request in order to know which layer it contains and what operations are supported: http://localhost:8083/geoserver/ows?service=WFS&version=1.0.0&request=GetCapabilities

   

   GetCapabilities response

   If we scroll below, we will find the Counties feature type described:

   

   GetCapabilities response (Counties feature type)

5. Now let’s request more information for the Counties layer using a DescribeFeatureType request:

   http://localhost:8083/geoserver/ows?service=WFS&version=1.0.0&request=DescribeFeatureType&typename=geosolutions:Counties

   Which gives us information about the fields names and types as well as the geometry type, in this case MultiPolygon.

   

   DescribeFeatureType response for Counties feature type

6. After that, we can issue a basic GetFeature request, that looks like this:

   http://localhost:8083/geoserver/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=geosolutions:Counties&featureId=Counties.1
   

   Note

   Notice it’s almost the same as the one that Geoserver generated, but it’s requestin a single feature specifying its identifier via featureId=Counties.1

   In the next section we will see how to filter the WFS output based on various attributes.