In GIS parcel layers, I find that users tend to assume that APN (assessor parcel number) represents a unique key for each parcel geometry in a County. Nine times out of ten, this assumption is wrong, and results in an inaccurate analysis. The best solution is to create a parcel layer in which APN is a unique key....
Jeff - Thanks. I’m happy you found it useful.
The short answer is that you treat situs address as just another column in the assessor role - just like APN and assessed_value. That is because in (almost) every County’s assessor database, there is an overly simplistic one-to-one relationship between APN and situs address. It’s an unsatisfying answer, but site address data in assessor tax roles is equally unsatisfying.
The long answer is that, for a series of reasons, you shouldn’t rely on the Assessor’s tax role for accurate and complete site address data in the first place. The right solution is to use an Enterprise Addressing System that manages the geospatial dimension of addresses and their complex relationships to parcels separately from the assessor tax parcel system.
Maybe I’ll make my next blog post on the pitfalls of assessor data for site addresses and the virtues of Enterprise Addressing.
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Adam - very informative post, thanks! If more than one parcel has the same APN, how do you deal with the situs address that comes from the assessor’s tax roll?
By Jeff Hobbs on 2012-03-17