.. |spherical-mercator-intro| replace::

  This document describes the Spherical Mercator projection, what it is, and
  when you should use it. It includes some background information,
  demonstration of using the code with just a commercial layer, and how to add
  a WMS over the top of that layer, and how to reproject coordinates within
  OpenLayers so that you can reproject coordinates inside of OpenLayers. It is
  expected that readers of this tutorial will have a basic understanding of
  reprojection and a basic understanding of OpenLayers.