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New automated techniques to validate and populate property valuations
1. New Automated Techniques to Validate
and Populate Property Valuations
International Property Tax Institute Commercial Properties Conference
May 3 and May 4, 2012 Montego Bay, Jamaica
Robert.Carroll@Pictometry.ca
Pictometry Canada
2. Overview
New challenges
Austere Budget: resources, manpower, fleet costs
Revenue Pressures
Inaccurate/Inefficient Legacy Procedures
Public Transparency
New opportunities
6. Opportunities
• New standard of field review - IAAO 3.3.5
• Desktop appraisal is now standard procedure
• Pictometry is single-source supplier remote
desktop appraisal data:
Metric georeferenced ortho, oblique, street-
side imagery
ChangeFindr automatic building change
detection
Sketch Check compares building sketch with
geographic data
CAMA integration
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14. ChangeFindr – What is it?
ChangeFindr is a building outline creation and
analysis service providing automated change
detection between two respective years of aerial
imagery.
The combined technology enables GIS
professionals, real property tax agencies,
planning departments, and public safety users
to more easily compare changes in land and
property features between existing county aerial
photos and new imagery of the same area.
15. Change Detection
……detects changes in an area that could
go undetected, such as additions to
existing structures, demolitions, land use
changes, new construction, or other real
property features.
The process includes the ability to create
GIS polygon “building outlines” and analyze
them for changes in size and shape.
16. Target of Services
Residential, Commercial, and Industrial
Buildings
•Isolated Garages, Mobile Homes, Sheds
•Greenhouses and Silos
•Water Storage Tanks
•Other features with a roof
17. Not Target of Services
Vehicles, Boats, Ships
•Pools
•Paved areas
•Bare ground surrounded by a fence or wall
•Steel Tower/Frames, Antenna, Cell phone towers
•Billboards
•Tombstones
•Changes in the vertical direction (e.g. a one story
building that is renovated to a two story building)
18. Steps in the Process
1. Building Outline Creation (BOC)
3. Change Detection (CD)
20. Change Detection
Example: Outlines are compared to
historical imagery to update the outline
file
Building outline Latest imagery Updated
Building outline
21. Deliverable Products
Primary deliverable is a geospatial
database of building outlines
Attributes of the deliverable include…
Parcel ID
X,Y coordinate of center of building polygon
Change Detection Classification – Existing,
Changed, Destroyed, New, Possibly Changed
22. Enhanced Features
Assigning Colors/Themes by status type
Regional Status Report
statistical results for the regions defined by the
customer (e.g. townships, wards).
Lengths of the Building Sides
Table lists lengths of the sides of the buildings
Percentage of Change
Added columns to Building Outline table for
“Orig_Area” and “ChangeRate”
39. Accuracy- Change Detection
The process is better than 98% accurate
•False Positive Rate: ratio of buildings with
fault state for all Changed/New/Demolished
buildings ≤ 2.0%
•False Negative Rate: ratio of buildings with
fault state for Existing buildings ≤ 0.2%
40. Proven Return On Investment
Geauga County, Ohio
51,000 Parcels
2004 - $1.8 million in
property value was found
after reappraisal data
collection was performed.
$35,000 in tax revenue on
a $17,500 investment.
After a 2nd ChangFindr
Project with new imagery
the following was reported
41. Geauga County ChangeFindr Results - 2004-2007
District $ Value Found $ Dest. Prop Net $ Value Assessed Value Tax rate Approx. Tax Amt
Auburn $292,200 $1,700 $290,500 $101,675 0.059239558 $6,023
Bainbridge $156,100 $4,700 $151,400 $52,990 0.066361555 $3,516
Burton $336,400 $0 $336,400 $117,740 0.040108602 $4,722
Burton Village $32,400 $0 $32,400 $11,340 0.042306082 $480
Chardon Twp $130,200 $0 $130,200 $45,570 0.050454279 $2,299
Chardon City $44,300 $3,000 $41,300 $14,455 0.051471305 $744
Chester $602,400 $4,200 $598,200 $209,370 0.057045359 $11,944
Claridon $205,800 $0 $205,800 $72,030 0.040697997 $2,931
Aquilla Village $21,200 $0 $21,200 $7,420 0.052988997 $393
Hambden $323,200 $0 $323,200 $113,120 0.052204926 $5,905
Hunting Valley $0 $0 $0 $0 0.050284185 $0
Huntsburg $446,300 $3,000 $443,300 $155,155 0.04814363 $7,470
Middlefield $814,600 $6,000 $808,600 $283,010 0.046251006 $13,089
Middlefield Village $3,300 $0 $3,300 $1,155 0.045118574 $52
Montville $217,100 $0 $217,100 $75,985 0.041318239 $3,140
Munson $151,200 $1,200 $150,000 $52,500 0.052656419 $2,764
Newbury $569,900 $0 $569,900 $199,465 0.047635053 $9,502
Parkman $742,900 $4,800 $738,100 $258,335 0.045080778 $11,646
Russell $298,900 $33,300 $265,600 $92,960 0.056766935 $5,277
South Russell Village $31,200 $0 $31,200 $10,920 0.066651042 $728
Thompson $107,100 $0 $107,100 $37,485 0.04251769 $1,594
Troy $151,100 $0 $151,100 $52,885 0.043594487 $2,305
Total $5,677,800 $61,900 $5,615,900 $1,965,565 $96,526
Provided by the Geauga
County Auditor's
Office Tracy A.
Jemison, AAS
Auditor
43. A Sketch Verification Solution
Sketch Check Benefits
•
Quickly verify whether current
sketches in CAMA system are
correct
•
Reduce field visits and allocate
staff resources more efficiently
•
Increase tax revenues by
identifying previously undetected
property changes
•
Convert sketches into geo-
referenced shape file layer that
can be used in GIS
44. Sketch Check Target Market
Primary Market:
• Assessment / Appraisal
• Target ChangeFindr customers &
customers who have adopted
IAAO standards
Secondary Markets:
• The geo-referenced building
footprint shapefile layers have
value for other departments such
as Zoning, Planning and E911
45. How Sketch Check Works
•
Sketches are extracted from CAMA
•
Sketch Vectors are:
•
Geo-referenced
•
Overlayed on ortho imagery
•
Rotated to best fit
•
Flagged / Categorized appropriately
•
Out of scope for Pictometry Sketch Check:
•
Sketch correction
•
Sketch creation
46. Definition of Categories
•
Match – Sketch matches building
•
Minor Mismatch – Minor amount of the building’s outline does not match
between the ortho & the sketch (~ 100 square feet or less*)
•
Major Mismatch – Significant amounts of the building’s outline does not
match between the ortho & sketch (~ 100 square feet or more*)
Match •
No Bldg – No building appears in the ortho for the corresponding sketch
•
Undeterminable – Substantial amounts of the building outline cannot be
determined from the ortho—typically due to tree cover
•
New Construction – New construction or additional building is in the ortho,
but no sketch was provided—only indicated for parcels where a sketch
already exists w/in the parcel
•
Unable to Geo-reference – Assigned to parcels that contain sketches for
Major Mismatch which the vector data could not be processed or there were multiple nearly
identical buildings on the same parcel (so sketches cannot be matched to
buildings). This flag is only provided in the scoring table and associated
shapefile.
* As determined by visual comparison—not by actual measurement
New Construction /
Additional Building
47. Requirements Data
• CAMA and Sketch system type
• Sketch vector data in electronic format:
•
Preferable formats: Shapefile or Apex.
•
We cannot process image files such as JPG, PNG or IMG but there
should be a digital sketch file used to make that image file in the
CAMA system
•
For proprietary formats, Pictometry will work with sketch providing
vendor to acquire converted data, which may require conversion fee
• Parcel layer: Shapefile or comparable format that contains a unique
identifier for each parcel
• Ortho tiles
•
12” GSD or better, RBG, projected, with world files
•
Acceptable formats: ECW, JPEG or TIFF
• Ortho tile grid shapefile: shapefile that defines the ortho tile layout
• Regional shapefile (Optional): For incremental delivery purposes (not
reporting)
48. Customer Deliverables
• Shapefiles containing geo-referenced
sketches as polygon feature classes
- Each category
- All file
• Scoring Table (Excel & Shapefile format)
• Summary Report
• Customer Documentation
Detail on Reports
49. Sketch Check vs. ChangeFindr
•
Pictometry Sketch Check &
ChangeFindr help assessors
improve productivity & increase
tax revenues by quickly identifying
undocumented improvements.
•
Objective of Sketch Check is to
VERIFY whether data is accurate
•
Objective of ChangeFindr is to
DETECT CHANGE within a
jurisdiction
Yellow:Sketch Check Layer •
ChangeFindr can be positioned as
Red: ChangeFindr BOC an aid for future sketch management
Note: Sketch Check shapefiles cannot be used for ChangeFindr projects & vice versa
50. Advantages
• Imagery (ortho/oblique/street-side):
enable desktop review
• Change Detection: Identify parcels with
building changes
• Sketch Check: Identify data accuracy
issues.
• Prioritized Review: Scoring Table makes
it easy to prioritize which parcels to review
first
• CAMA/Workflow integration
• Single Source: Pictometry offers all
components of IAAO’s standard for
remote desktop appraisal
