Fair and Equitable Taxation: Why Good Data isn’t Good Enough

By Billy Burle, VP Sales and Marketing, SDS

Vince Lombardi once said “practice doesn’t make perfect, only perfect practice makes perfect”. This is one of those quotes that just sticks with you and can be applied to so many parts of our daily lives. It reminds us in work and play to step back and ask am I just practicing or am I truly perfecting what I do?

For the assessment and parcel mapping community, ensuring fair and equitable taxation for your constituents is something certainly worth perfecting, wouldn’t you agree?. Fair and EquitableTo do this there are many geospatial tools and programs you can leverage that help you take an auditing approach to ascertain the validity and reliability of your tax parcel information. To perform an audit of your real property we recommend you take multiple steps for identifying gaps or inconsistencies between graphic and non-graphic databases such as your GIS and CAMA data.

Steps to Performing a Real Property Audit™

There are various steps you can take to perform an audit that compares real property databases to ensure the right data is being used for proper assessments. As most modern CAMA systems use the sketch to derive a base value, the first step would be to export the sketches from the CAMA system. Once exported, they can be placed on the parcel centroid, scaled and rotated to match the orthophoto. This allows you to visually classify each sketch with potential error types such as undersized, oversized, or wrong sketch. An error report utilizing an automated analytic process that compares the sketch areas with what’s in the CAMA system can then be generated. This answers the question of do your CAMA sketches match what’s on the ground. In the examples below I think we can agree the answer is no. In these examples the blue polygon is the CAMA sketch and the red is what’s actually on the ground.



In addition to auditing sketches, it is necessary to validate the topology of your data. While topology may be typically checked during the edit process, some errors still slip through the cracks. The best way to identify these errors is to run a detailed and thorough topology audit to make sure that there are no gaps, dangles, overlaps, undershoots, or any other connectivity issues. These small and often overlooked errors can have a big effect on any analysis performed on the data. Another efficient method of locating errors in the data is to have an accurate orphan record report that identifies the following errors

  • Records in the graphic database with no match in the non-graphic property database
  • Records in the CAMA database with no match to the graphic database
  • Records in the CAMA database with multiple matches in the graphic database

The same tools used to produce the orphan record report can also used to verify whether or not the acreage (or square footage) in the CAMA and the acreage in the GIS match.


The art of perfecting what you do through more accurate data produces a whole host of benefits including:

  • Ensuring fair and equitable taxation
  • Fewer appeals due to better data
  • Discovery of missing tax revenue
  • Substantial reductions in field work
  • GIS & CAMA database become tightly coupled to eliminate future discrepancies
  • Increased level of public confidence

Audits can be performed internally if you have the extra staff and resources to dedicate enough time to get it done quickly and efficiently. If this is the case in your county then we encourage you to start the process for the betterment of your communities. For those that don’t have the resources, we have created a Real Property Audit™ Program that rolls all of the previously mentioned processes into one nice neat package. Once you become a part of the program we provide an independent review of the data, perform all of the various audit phases, and deliver back the coded sketch layer and a report of findings for each type of audit with recommendations. We also provide, for a limited time, an online GIS viewer with the errors color coded to help you visualize and review the discoveries. Whether or not this is a program you do internally or you look for a partner, I would ask once again are you practicing or perfecting?



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