# Data Stories: Populous Dutch Municipalities

We want to show the 25 Dutch municipalities with the largest
surface. Unfortunately, GeoSPARQL does not have an area
function. We therefore decided *to implement this function
ourselves in SPARQL*. We use the `geof:envelope`
function in order to extract the closest bounding box of a
municipality, for which we can calculate the area using simple
arithmetic and geometric conversion (from long/lat distance to
meters). The following shows the shape
of Baak
and the smallest bounding box that holds it:

## The biggest Dutch municipalities

We can now sort the municipalities based on their surface. The
following gives an overview of the 25 largest municipalities.
Zeewolde is larger than Amsterdam!

The same result can also be shown on a map. Notice that big
municipalities often have a large water surface.

## Most populous Dutch municipalities

Using SPARQL federation, we can dynamically pull in the
population numbers for each municipality. This allows us to
display the 25 most populous municipalities. With YASGUI, we
are able to put these results on a map and show nice popups
per result. The popup shows the name of the municipality, the
population, the surface, and also links to the RDF resource
(using URI dereferencing).