Using the PyQGIS library

In the previous section, we looked at a number of classes provided by the PyQGIS library. Let's make use of these classes to perform some real-world geospatial development tasks.

Analyzing raster data

We're going to start by writing a program to load in some raster-format data and analyze its contents. To make this more interesting, we'll use a Digital Elevation Model (DEM) file, which is a raster format data file that contains elevation data.

The Global Land One-Kilometer Base Elevation Project (GLOBE) provides free DEM data for the world, where each pixel represents one square kilometer of the Earth's surface. GLOBE data can be downloaded from http://www.ngdc.noaa.gov/mgg/topo/gltiles.html. Download the E tile, which includes the western half of the USA. The resulting file, which is named e10g, contains the height information you need. You'll also need to download the e10g.hdr header file so that QGIS can read the file—you can download...