Parcel to Assessment matching

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Initial Remarks

LightBox is always looking for the richest data possible when assembling datasets. We have found that Parcel and Property attribution is best if sourced from the county who maintains this data. We have also found that there are a different departments at the county who create and manage each piece of data. The GIS department at the county is motivated to maintain the parcel data along with some attribution. The assessor's office is motivated to maintain the property attribution, as it is a source that dictates the tax that is paid each year by the property owner. To create the best dataset we need to source from both departments and then join each dataset together to create a robust and confident offering.

APN to APN matching is simple

We hear from many users that the assumption of matching this data is simple because it is APN based and derived from the same county typically in the same building.

Over the many years that we have been working on this process we have found that this is far from the case. Matching is challenging at best. Each county is different and some are easy and some are difficult.

Some factors to take into account are:

Departments that do not communicate with each other.
APN formats can be different between the two departments.
Addresses are not always reliable since many properties do not have an address. e.g. Vacant Land.
Timing between an annual tax roll released vs a parcel release.
GIS departments lacking resources to maintain the pace.

"I was able to get a 85% match with some work"

We agree with this statement, however we do not stop at 85%, the challenge is getting to as close to 100% as possible. This is where the LightBox experience, diligence, and attention to detail comes to play.

"Should I expect a 100% match rate?"

Since data is collected from different departments it is rare that we have a 100% match rate. It is expected to have a variance from 100%.

Timing between Tax Roll and Parcel acquisition.
Some parcels are not tracked by the tax assessor.
- Right-of-ways
- Forest land
- Rural government land
- New development that only exists either in the tax data or the parcel data

We have a process that has been continually refined over the last 20+ years. This process consists of a set of steps across all counties and then a set of steps that is unique to each county.

Some examples of these steps:

APN to APN
Modified APN to APN
Tax ID to Tax ID
Address to Address
Special Rules
Owner Name

QA Process

During the automated processing the metrics from the previous matching percentages are taken into account. If our automated process is outside of a set threshold we will then route this data back to our QA team for review. If it is within our threshold we will send the data to our master database.

Orphan Assessments

Given the matching logic used, it is understandable that not all parcels are matched to assessment records. Those assessment records have value even without a match to parcel data. They carry a majority of the attributes and can be used for search and analytics. Orphan Assessments do carry a spatial attribute (point). Since a parcel is not linked to Orphan Assessments the point is derived from a street centerline geocode.

Orphan Assessments amounts change depending on when new parcel data is sourced.

Delivery Methodology

LightBox takes the stance that you should receive all the data that we have on a topic, matched or unmatched. That is why in some packages you will see a OrphanAssessment table. This table contains the assessment attribution of records we were unable to match to a parcel. There will be a point associated with the record but this point will be geocoded to a street centerline geocode because we do not have a parcel related to this record.

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Table of contents

Initial Remarks 
LightBox Matching Methodology
QA Process
Orphan Assessments
Delivery Methodology