About the Pima Property Values Map

November 28, 2023

The Pima property values map shows values per square foot of most single-family residences in Pima County, according to data from the County Assessor. 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 2024 and reflect the most current appraisals.

This map shows the 307,691 residential parcels appraised via the Assessor's mass appraisal system. 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 got me close to 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 307,691 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.