Boulder County Assessor's Office GIS staff work hands on with appraisers to improve data/attributes for mass appraisal. You will get a brief overview of how GIS is used to facilitate fieldwork, find and fix inaccurate attributes, and speed up the review and update of property information. Topics covered will include the mapping of features known to affect property values, as well as those not always associated with mass appraisal. Additionally, differences between data gathering for properties in the mountains vs. plains will be highlighted.

1. Getting it Done
Using GIS to Help Appraisal Staff Rapidly Update
and Improve Property Data
Pete Coventry, Adam Hoppe
Boulder County Assessor’s Office
GIS Department
Boulder, Colorado

2. Overview
• Boulder County
• Assessor’s Office structure
Data Mining
• From the Assessor’s Database
• Getting it into GIS
Focus on Residential Properties

3. GIS for Appraisal work
• In the field
• Capturing Attributes (valuation)
•
Analysis & Modeling

4. Where we work
Geology.com

5. Where we work
720 square miles
One-third plains
Two-thirds mountains
125,000 real properties
98,000 residential

6. Diverse Landscape

7. Diverse Properties

8. How we work
Why is property Assessed
• Basis for generating tax revenues for local services
Assessors Role
• Identify and values property within the county in
accordance with state law
• Equalize property values/
taxes distributed fairly
Re-valued every odd # year

9. Teams = Geographic Areas

10. Assessor’s GIS Department
Led by Cindy Braddock
• 3 GIS Specialists
• 3.5 GIS Techs
Responsible for… A LOT!

11. Data Mining
Why and How
• Requests for information
– Public, partners, other County
departments
• Helps us improve quality of information
• Understand what we’ve already got
– Right, Wrong, Inconsistent
– Know what to fix

12. 100’s of tables
1000’s of fields

13. Add tables
Join on Key Field
Set requirements/parameters

17. “Bubble”
Maps

18. Permit Fieldwork
• Status as of January 1st
• Remodels, other high $ improvement adds
value
• Generates tax revenue for our districts
• New residential construction
– Vacant to residential changes assessment rate
– Determined by existence of a foundation

23. Mountain Attributes
Human Judgment:
• View
• Privacy
• Access

24. Mountain Attributes
GIS Terrain Analysis captured:
• Topography
• Aspect

26. Dick’s Views on Views

30. Field Data -> Excel Spreadsheets->
Mass Uploaded into Database

31. Examining Sales Ratios
Sales Ratio =
Estimated Sales Price (ESP)/Time-Adjusted Sales Price
• Any ratio between 0.95 and 1.05 is ‘acceptable’
• Sales ratios << 1.00 – UNDERVALUED ESP?
• Sales ratios >> 1.00 – OVERVALUED ESP?
• Cause: incorrect or missing property information?

37. Planes, Trains & Automobiles…

45. Planes, Trains & Automobiles…
Actually… Power Lines, Towers, and Railroads

54. Planes, Trains & Automobiles…

55. …Automobiles (Traffic, really)

64. GIS Analysis

65. The Heartbreak of…

67. http://geology.com/articles/expansive-soil.shtml

69. 2008

70. 2008 - 2009

71. 2008 - 2010

72. 2008 - 2011

73. 2008 - 2012

79. Thanks for attending!
Any questions??
Adam Hoppe – ahoppe@bouldercounty.org
Pete Coventry – pcoventry@bouldercounty.org
Adam Hoppe & Pete Coventry
Boulder County Assessor’s Office
GIS Department
Boulder, Colorado

81. Geographic Areas = 5 Models

82. Sales Ratio = 1.6
•
•
•
•
•
Sold for $514,000
TMADJ SP = $513,000
ESP = $800,000
Overvalued ESP
Time for review

83. Sales Ratio = 0.81
•
•
•
•
•
Sold for $675,000
TMADJ SP = $660,000
ESP = $540,000
Underestimated ESP
Appraiser will review property
attributes to determine if
incorrect or missing

87. Coming Soon…
Bye, bye ArcReader
Hello ArcGISExplorer
• More bells and whistles and flexibility for the
users (appraisers)
• Much Faster
• More customization on the front end which
helps deliver more useful maps
• More programming… C#