Addressing--The Science of Eclectic Interpolation

Author: Larry Wolfson
Organization: Maricopa County

2901 W. Durango St.
Phoenix, AZ 85009
USA

Phone: 602-506-4686
Fax: 602-506-8594
larrywolfson@mail.maricopa.gov

You've got a great road network. The streets that you've spent months digitizing from the latest aerials have been GPS verified for +/- 25 feet. It puts the TIGER cover to shame, making missing arcs and attributes obvious. There's only one problem. You can't find half the addresses for your voters with any degree of reliability so you have to fall back on the old flat files to get your work done. The Assessor, Planning and Development, Fire, and Sheriff's departments are asking, "What use is this GIS if it can't improve the response time that our customers demand?"

Accurate geocoding depends not only on an accurate road base but also on an accurate address database. In our experience, we have found at least nine databases with address ranges at our disposal including 911, elections, postal, TIGER, GDT, BLR, assessor, planning, and Maricopa Association of Governments data. All contain some resemblance to their real-world counterparts. All contain disparate data in relationship to each other.

As one of the largest, most rapidly growing counties in the nation, with 26 separate political jurisdictions, we feel that lessons we have learned may be instructive for other rapidly growing counties and/or jurisdictions. As a brief outline, the following topics will be discussed:

1. Description of problem: Existing attribute files contain a number of addressing errors ... overlapping ranges, reversed sequences, and/or reversed odds/evens. Also many roads lack official names/identification (which is a problem common to many rural areas where roads have been named informally by local residents).

2. Why bother fixing these problems? Flood control, planning, elections, environmental, and emergency services all depend on accurate addresses.

3. How the MCDOT GIS has resolved thorny database issues:

a. Obstacles: Lack of data sharing between agencies, incorrect addresses assigned by County planning, sheer magnitude of project versus available resources, conflicting names inherent in a multiple jurisdictional environment, multiple virtual addressing grids, circular design of planned development communities, automated database comparison versus physical field checks, assigned versus signed road names, and incorporation of new attribute data into an ArcStorm environment.

b. Solutions: Specific tactics used to overcome our obstacles.

4. Lessons learned.