The map below shows values per square foot of residential properties in Pima County. You can view it in a full browser window by clicking here.
Interact with the map by zooming in and out, and clicking on the dots to see individual property characteristics.
The data
The appraised value and square footage data shown here was obtained from records publicly available for download on the Pima County Assessor’s website. The values shown are for tax year 2023 and reflect the assessor’s most current appraisals.
This map shows the 304,486 parcels treated as “residential” by the assessor. Each is represented by a color-coded dot, colored according to its value per square foot. (See the key in the bottom right corner of the map.)
A vector tile approach
300K is too many features for a client-side mapping system like Leaflet to render. Instead, this map's features are displayed and accessed using vector tiles, which I created using a cool program called Tippecanoe. Tippecanoe inputs a GeoJSON file and outputs a vector .mbtiles file, which can then be uploaded to mapbox.com and styled using Mapbox Studio.
The algorithms in Tippecanoe aim to represent the texture and density of your data at any level of zoom. They're complex, and the user has the option of specifying all sorts of parameters. But I found that just using the "Try this first" command example in the program's README file provided exactly the result I was looking for.
Adding interactivity
One of the things that makes this map special is its ability to quickly show attribute data in a pop-up window for any of its 304,486 features. Click on one of the dots, and the map will show you that property's address, value, square footage, and value per square feet. I developed this feature using the Mapbox GL JavaScript Library, which allows for client-side rendering of vector tile data in the form of pop-ups, hover effects, and so on.