Preparing the workspace

First of all, we should choose a small area to work with. A populated town or city is an obvious choice for this task. The first obstacle is that there aren't any freely available settlement polygon data in the formats we are used to. To tackle this, we can download the required data directly from OpenStreetMap. OSM offers a read-only web database for accessing its data, which is available through the Overpass API. From Overpass, we can request data through regular web requests, and the server sends the matching features as a response (Appendix 1.5). In QGIS, we can install a plugin written directly for this--QuickOSM. Therefore, our first task is to install the QuickOSM plugin as follows:

1. Open the plugin manager via Plugins | Manage and Install Plugins.
2. Type QuickOSM in the search field.
3. Click on Install plugin.

In QuickOSM, we can build Overpass requests in an interactive way. In Overpass, we can query features in a predefined area (for example, the extent of a layer...