Recently I've enjoyed playing around with some MassGIS Data - speficially, the MBTA Rapid Transit data as well as the census data, for city locations.
Here's what it looks like if we draw massachusetts:
Now, let's zoom in and overlay the MBTA data:
We can calculate the voronoi diagram, and draw that as well: O(n log n) voronoi algorithms (such as Fortune's) are hard, so eventually I eneded up implementing a O(n2) algorithm which you can find described here.
We can use this diagram to generate a sort of heatmap, showing proximity to the nearest subway station: I'm still not happy with this visualization. I didn't want to draw the Voronoi diagram lines, but due to what I think are SVG rendering nuances, I couldn't get the gradients to line up perfectly no matter how hard I tried. The voronoi lines serve to mask the edges.
It took me awhile to put this page up, because I wasn't happy with the size (in bytes) of the SVG files I was generating. This page would have been many megabytes more than it already is! I was able to use a combination of two things to get the size down
- When outputting the SVG files, limit the floating point output accuracy to two decimal places
- Use the Ramer–Douglas–Peucker algorithm to simplify both the MBTA and Census geometry