Working with GIS data manually

Let's take a brief look at the process of working with GIS data manually. Before we can begin, there are two things you need to do:

• Obtain some GIS data
• Install the GDAL library and its Python bindings so that you can read the necessary data files

Obtaining the data

Let's use the US Census Bureau's web site to download a set of vector maps for the various US states. The main site for obtaining GIS data from the US Census Bureau can be found at http://www.census.gov/geo/www/tiger.

To make things simpler, though, let's bypass the web site and directly download the file we need from http://www2.census.gov/geo/tiger/TIGER2014/STATE/tl_2014_us_state.zip.

The file, tl_2014_us_state.zip, should be a ZIP-format archive. After uncompressing the archive, you should have a directory containing the following files:

• tl_2014_us_state.dbf
• tl_2014_us_state.prj
• tl_2014_us_state.shp
• tl_2014_us_state.shx

These files make up a shapefile containing the outlines of all...