Adding WMS layers

Web Map Service (WMS) is a standard developed by the Open Geospatial Consortium (OGC) implemented by many geospatial servers, among which we can find the free and open source projects GeoServer (http://geoserver.org) and MapServer (http://mapserver.org). More information on WMS can be found at http://en.wikipedia.org/wiki/Web_Map_Service.

As a very basic summary, you can understand a WMS server as a normal HTTP web server that accepts requests with some GIS-related parameters (such as projection, bounding box, and so on), and returns map tiles forming a mosaic that covers the requested bounding box. Here's the finished recipe outcome using a WMS layer that covers the extent of the USA (source code can be found in ch02/ch02-wms-layers/):

Note

We are going to work with remote WMS servers, so it is not necessary you have one installed yourself. Note that we are not responsible for these servers and that they may have problems, or may not be available any longer when you...