When the National Zoning Atlas set out on an ambitious project to democratize national zoning data, they came to Regrid's Data With Purpose program. Data With Purpose provides parcel data to nonprofits and academics on a "propose your own budget" basis, and outfitted the National Zoning Atlas team with nationwide parcel data that could greatly accelerate their work and increase its precision.

The National Zoning Atlas is a collaborative project digitizing, demystifying, & democratizing ~30,000 U.S. zoning codes. It was founded by Sara Bronin, a Cornell University professor who developed the methodology in 2020, and has involved over 300 collaborators.

The spatial framework of parcel boundaries from Data With Purpose provides an accurate geographic canvas, allowing zoning classifications to be meticulously mapped over each individual parcel. This overlay process ensures that zoning information aligns with real-world property lines, enhancing accuracy by clearly delineating how different zoning rules apply to specific parcels of land.

The following is an interview with Scott Markley, Geospatial Project Coordinator for the NZA, detailing how Regrid parcel data is supporting the important work of the National Zoning Atlas.

If you're interested in applying for Data With Purpose, we invite you to do so here.

Alex Alsup: How does the NZA team integrate Regrid’s nationwide parcel data into the Zoning Atlas and how is it supporting the work of developing the NZA?

Scott Markley: We are currently using Regrid data in three main ways.

First, we use Regrid’s parcel polygons to build our zoning districts where jurisdictions do not have GIS data to share with us. Frequently, smaller municipal and county governments only have a PDF map to share. After georeferencing that PDF and overlaying it on top of the Regrid parcels, our analysts then select and assign parcels their appropriate zoning code and then aggregate them into their zoning district geometries. This process is much faster and more accurate than the alternative of tracing each zoning district by hand.

Second, Regrid’s parcels add an important reference layer when we adjudicate boundary disputes. Zoning district polygons are often poorly drawn, resulting in large gaps or overlaps in the data. Parcel boundaries are useful for correcting these because they typically show where the zoning district boundary should have been drawn.

Finally, we use Regrid’s parcels to standardize the geometries of our zoning districts. Some municipalities remove rights of way from their zoning districts, while others leave them in, disrupting how we can analyze and compare land areas covered by certain zoning designations. In many places, Regrid’s data already have those rights of way removed. In other areas, Regrid has provided a flag indicating whether or not that parcel is likely to be a right of way. In both cases, we use this information to remove rights of way from our zoning districts, rendering them comparable across jurisdictions.

AA: Looking ahead, how do you envision the role of Regrid’s data evolving within the NZA's framework? Are there potential new applications you are considering with the data?

SM: A portion of the Regrid parcels include zoning code information. We have started to collect and aggregate those parcels by zoning district and jurisdiction, which speeds up our process, but we still need to verify these outputs against the zoning code text and account for overlay districts before publishing them.

In addition, as we start to produce some regional snapshots with the NZA data, we are looking into other parcel-level variables that we can combine with the zoning data, such as information on ownership, land use, building counts, building footprint areas, and unit counts.

AA: Is there any noteworthy feedback you've received from contributors working on the development of the NZA who've used the Regrid data?

SM: Our contributors have found the Regrid data to provide an excellent set of building blocks to create the Zoning Atlas. Even when parcels do not cleanly align with zoning district boundaries, splitting parcels is preferred to building the zoning districts from scratch.

Regrid parcel data has been an extremely convenient data source for building our zoning districts. 

To learn more about the National Zoning Atlas, click here.