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Mapping/GIS Projects with Documented Return on Investment
Appraisal Map Evolution
Williamson County StatisticsMaps & Records Department StatisticsMaps & Records Department TimelineGIS Project Benefits
Williamson Central Appraisal DistrictGeorgetown, Texas
Where are we?Williamson County Statistics
Williamson County Statistics
Growth Rate – State of Texas
Williamson County Population F 1970 - 2010 Williamson County Statistics
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Growth Rate Austin Metro Area 2000 – 2010 37%Williamson County Rate
2000 – 201069 %
1990 – 2010203 %
1980 – 2010452%
1970 – 20101,033%
Williamson County Statistics
Growth Rate – 9th fastest growing county in the nation in 2009.
Williamson County Statistics
Kendall County, IL
Pinal County, AZ
Rockwall County, TX
Flagler County, FL
Loudoun County, VA
Forsyth County, GA
Lincoln County, SD
Paulding County, GA
Williamson County, TX
Douglas County, CO
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Growth Rate – New Sub Lots 10 Year Average = 7,100 per year
Williamson County Statistics
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Williamson County Statistics
2011 Real Property
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VACANT27,582
IMPROVED139,735
TOTAL167,317
Growth Rate – New Improvements10 Year Average = 5,835 per year
1993 – Mylar Map Maintenance
Maps & Records Department Timeline
1993 – WCAD has desire to begin GIS project1994 – GIS Pilot Project completed
Purchased used PC’s, free software from vendorNo GIS budget
1995 – All map maintenance digital - no more drafting!Traded a set of paper maps for scanned images100% digital– raster/vector hybrid mappingConversion progress limited to map updates onlyNo GIS budget
1996 – Parcel conversion process – very s-l-o-wNo GIS budget Chief Appraiser retires
Maps & Records Department Timeline
1997 – Begin Phase I Parcel Conversion ProjectLimited GIS budgetNew Chief Appraiser hired
1998 – Phase I Parcel Conversion Project CompleteRealistic GIS budget (conversion funding)
100% vector mapsBegin GIS software analysis training – FAILURE.
1999 – Begin Phase I Network Infrastructure UpgradeBegin replacing ALL dumb terminals with PC’sGIS budget includes analysis software & trainingNo aerial imagery budget
Maps & Records Department Timeline
2000 – Complete Phase I Network Infrastructure UpgradeWCAD hires vendor to host www.wcad.orgWebsite with interactive mapping Tried In-house geo-referencing – FAILURE Record number of new subs filed (over 9,000)
2007 – Begin Phase II GIS Conversion Project (software)GIS budget (software conversion funding) Joined consortium to purchase oblique imagery
2008 - Complete Phase II GIS Conversion Project (software)Received first set of oblique imageryGIS budget includes software & training dollarsRe-train M&R GIS staff on new softwareBegin parcel maintenance using new GIS software
Maps & Records Department Timeline
2009 – Begin/Complete Phase III GIS Conversion Project (rectification)Oblique & ortho imagery in budget (6 years)Parcel rectification complete!Change detection funding in budgetSketch verification initialized (all improved
property)2010 – Utilize GIS tools
Appraisal analysis/defenseChange detection utilizedSketch validation for new improvements only
Maps & Records Department Timeline
Parcel layer not user friendly to our staff or taxing units prior to 2008.Our parcel layer required several tools to take
from deed to map and additional tools to analyze data.
The maps created were in an uncommon format not useable to our taxing units
Conversion to GIS system that Taxing Units were using became necessary.Streamlined internal processCreated useable maps for our taxing units
Conversion to Common GIS Mapping Software to Benefit Efficiency & Taxing Units
Our data was then in a common format with the Taxing Units but required additional manipulation to be useful.Taxing Units still had to rectify our parcel layer.Unprofessional appearance to the public and other users
implied that our map work was less than trustworthy.Answer = Parcel Rectification
Studies conducted to determine feasibility of doing this rectification internally proved to be cost prohibitive.
Early 2009 we published a Parcel Rectification RFP.Late 2009 rectified parcel layer completed.
Enabled Taxing Units to use our parcel layer without additional work and created professional and accurate appearance to maps – which in turn increased our credibility.
Common Mapping Software but....
Parcel Layer Not Geo-referenced
Parcel Rectification – Before & After
Consortium formed between larger taxing units and appraisal district to purchase imagery.Pros:
Cost sharingCons:
Imagery only available to those who participatedLack of complete control for appraisal district
Appraisal District purchase of imageryPros:
Shared cost through contributions via appraisal district budgetComplete control of imagery by appraisal districtImagery available to ALL taxing units
Cons:Cost prohibitive to appraisal district if taxing units do not see the
benefit
Ortho & Oblique Aerial Imagery Purchase
Oblique Aerial Imagery
Now that the imagery is available what else can you do with it???
Answer: Sketch ValidationSketch vectors exported from CAMA system
Geo-referenced, rotated, and anchored to the structure on the aerial ortho image.
GIS sketch layer createdInvalid findings greater than 100 square feet identified
Using this process ALL sketches of improvements are validated and can be considered as digitally re-measured
Appraisers work with the validation software to correct any invalid sketches from a queue.Increases accuracy of sketches and adds missing value to the
appraisal role.
Sketch Validation
Upon completion of the project, the vectors are delivered in a GIS shapefile format.
Manual re-measure estimated cost*:WCAD Improved Properties (2009) = 135,000(x) Re-measured per hour = 6Hours to Re-measure = 22,351 = 10.75 years(x) Avg. Appraiser Salary = $60,000Estimated Cost of Manual Re-Measure =
$644,740Gained taxable value needed to recover $644,740 =
$28,655,120 * This estimate is only Appraiser Cost (No Entry)
Why Do Sketch Validation?
Sketch Validation Software & Service Cost:WCAD Improved Properties (2009) = 135,000(x) Sketch Validation Cost Per Parcel = $0.43Estimated Sketch Validation Cost =
$58,050Gained taxable value needed to recover $58,050
= $2,580,000
Estimated Cost of Manual Re-Measure =
$644,740Estimated Sketch Validation Cost =
$58,050
Sketch Validation Results:11% invalid findingsTotal value added to role: $88,530,128Estimated Total Taxes in Year 1: $2,213,253
Return on Investment for Year 1 Taxes Gained = $2,213,253Total Cost to District = $135,620
ROI = 1632%
Accuracy of the appraisal role with fairness and equality of valuations
Added value to role that increases tax base by adding missing improvements
Cost effective when compared to manual re-measure
Huge Return on Investment of monies contributed to your budget by the taxing units
Increased credibility
Sketch Validation:Uses sketch vectors currently in your CAMA systemOverlays sketches on most recent aerial photographyEnables correction of invalid sketches efficientlyResulting in accurate sketches
Change Detection:Compares the most recent aerial photograph of an
improvement to a previous aerial photographChanges are detected from these photographsDoes NOT correct existing sketch errorsDoes correct missing improvements since last aerial
photograph
Sketch Validation Vs. Change Detection
• Convert to GIS software most commonly used by your Taxing Units
• Promotes data sharing• Purchase aerial ortho and oblique imagery
• Increased visibility of improvements • Shared use and expense with taxing units
• Geo-Reference (Rectify) your parcels • Enables immediate use of your parcel layer• Creates a more professional image to your
taxing units and the public (increased credibility)
Recommended Progression to Assist Taxing Units
Sketch Validation of Improvements Creates an accurate sketch of all
improvements within CAMA system Change Detection of Improvements
Continues accuracy of sketches by detecting changes from each version of your aerial photography
Recommended Progression to Assist Taxing Units
Thank You!Alvin LankfordChief Appraiser
Pamela OrrDirector of Operations
Williamson Central Appraisal District
625 FM 1460Georgetown, Texas
78626-8050(512) 930-3787
