Performing geospatial calculations

Shapely is a very capable library for performing various calculations on geospatial data. Let's put it through its paces with a complex, real-world problem.

Task – identifying parks in or near urban areas

The US Census Bureau makes available a shapefile containing something called Core Based Statistical Areas (CBSAs), which are polygons defining urban areas with a population of 10,000 or more. At the same time, the GNIS web site provides lists of place names and other details. Using these two data sources, we will identify any parks within or close to an urban area.

Because of the volume of data we are dealing with, we will limit our search to California. It would take a very long time to check all the CBSA polygon/place name combinations for the entire United States; it's possible to optimize the program to do this quickly, but this would make the example too complex for our current purposes.

Let's start by downloading the necessary data. We'll start by downloading...