The Regrid ID (ll_uuid)

The Regrid ID, available in the ll_uuid column, is our unique identifier for a single parcel. This ID remains stable across county data refreshes. This field can be used for tracking individual parcels.

County-provided IDs are often not unique or consistent

Most counties provide one or many parcel IDs. These are known by different names: Assessor Parcel Number (APN), Parcel ID (PID), Account Number, GIS ID, and many other variants.

There are no nationally adopted parcel ID standards. This means that the formatting of these IDs is varied. County-provided parcel IDs are often not unique nationwide or even within the county. Some counties will even re-use old parcel IDs on new, different parcels in the future.

The Regrid ID solves this by guaranteeing a universally unique ID for every parcel.

When does the Regrid ID stay the same, and when does it change?

Regrid IDs stay the same between updates when:

• The new parcel overlaps the old parcel in any way, and maintains the same unambiguous county-provided parcel ID
• The new and old parcels overlap each other to a significant extent, and no other conflicting parcels overlap with the same parcel ID or address

Regrid IDs are not preserved when:

• The old parcel has been split into new parcels, and all the parcels receive new county-provided parcel IDs. Counties often do this when, for example, farmland is turned into subdivisions.
• Parcels are combined, and the new parcel receives a new county-provided parcel ID. Counties do this when, for example, a corporate owner buys multiple parcels to build a large structure.
• Identical parcels overlap, and lack disambiguating attributes like a distinct parcel ID or address
• No parcel data was previously available. For example, parcels that have been newly digitized that are filling in previously blank areas on the map

What happens to the Regrid ID when a parcel splits or merges?

When a parcel is split or combined and new parcels created, the new parcels receive new Regrid IDs.

If the previous parcel is redrawn, split, or combined, but still overlaps the old boundaries and maintains the same county-provided parcel ID, the Regrid ID does not change.

Tracking parcel changes with ll_stable_id

The ll_stable_id field indicates if the Regrid ID for a parcel has changed or was newly assigned during the last refresh from the county.

A null value indicates a new Regrid ID was generated because the new data could not be matched to any existing data during the county data refresh process.

A non-null value means we were able to match the refreshed parcel with a parcel in our previous data. The available non-null values are parcelnumb, address, geometry, or preserved. The value indicates what attribute we used to match the refreshed parcel to the previous parcel. All matches include geometry overlap. The preserved marker is a legacy entry and indicates that the ll_uuid was carried forward from the previous data.

Can I track splits or combines with the Regrid ID?

You can use the ll_stable_id to identify parcels whose ID could not be preserved between updates. These parcels are often the product of splits or combines. We do not maintain a lineage file that directly links these IDs.

What should I do if a Regrid ID no longer exists?

If a Regrid ID no longer exists in the latest data, this means the original parcel has likely been split, combined, deleted, or otherwise not able to be confidently matched to the latest Regrid data.

In these cases, we recommend re-matching your original record to the latest parcel data using a point, address, or parcel ID. The parcel centroid is the most reliable method as the parcel ID, address, and/or the parcel shape have likely changed significantly.

Technical details

The ll_uuid is implemented as a v4 random uuid. There are 5.3×1036 possible variants, effectively meaning we would not expect the same UUID to be generated twice before the heat death of the universe.