identifying misplaced voters using a voter-precinct ... · identifying misplaced voters using a...
TRANSCRIPT
Identifying Misplaced Voters Using a Voter PrecinctUsing a Voter-Precinct
Verification Model
Steve Demers, Sacramento County Voter Registration and Elections
Sacramento CountySacramento CountyVoter Registration and ElectionsSteve Demers, GIS AnalystHelen Corbett, GIS Technician
Elections employees in attendance?
Identifying Misplaced Voters UsingIdentifying Misplaced Voters Using a Voter-Precinct Verification Model
The error that started it allHow voters are assigned to a districtExamples of errors that can go unnoticedThe GIS modelR i i th t tReviewing the outputsResults
M MMeasure M
November, 2006$750 Million School Bond issueFailed by 5 votesFailed by 5 votes7 voters outside the Improvement District inadvertently allowed to voteElection redone in March, 2007 with correct boundariesBond Measure passed
What to do to catch these errors before it’s too late
Districts
Precincts
District-Precinct-Segment-Address
Many-to-Many Relationship
Districts consist of many Precincts
Precincts are part of many different Districts
Precincts assigned Districts
Maintained in SQLNot Spatial
District-Precinct-Segment-Address
Streets or Street Segments exist
ithi th P i twithin the Precinct.
Valid addresses exist on the street segmentsegment.
Street Segments in a Precinct
Maintained in SQLNot Spatial
Registration Cards are input
Voters are assigned a Precinct automatically based on ranges of street segmentsstreet segments
E th t ti dErrors that can go unnoticed
Illogical Address
New Parcels, Parcel Boundary y
Changes
14300-14398 Precinct 77112
14400-14498 Precinct 77200
A i lid ddAn invalid address within a valid range
1800-1998 (Even) ( )Precinct 28324
1801-1999 (Odd) Precinct 28210
Th GIS M d lThe GIS Model
Geocode Voter Addresses to the best source available.Output the unmatched records.Spatially join Precinct # from Polygon features to all the matched records that land in it.Compare the Precinct Number in the Voter File (The PrecinctCompare the Precinct Number in the Voter File (The Precinct we think it’s in) to the Precinct Number from the join.Not equal—Output points as “Potential Errors” to review.
The Model
O t tOutputs
The Model
O t tOutputs
G d V t AddGeocode Voter Addresses
Voter File (…more than 65,000 voters?)Address Locator (Composite if possible)
S t t h d/ t h dSeparate matched/unmatched
Address Locator gives a Status M, T or UPut “Ties” with “Matched”
S ti l J iSpatial Join
Make Precinct LayerSpatially Joins Precinct ID to the Matched Records
Select/Output Records WhereSelect/Output Records Where Precinct IDs Are Not Equal
R i i th O t tReviewing the OutputsU t h d filUnmatched file.
Use the Review/Rematch Process
Manual Review(In a table)
Potential Errors file.Manual Review
(On map)
U t h d fil 727 RecordsUnmatched file
Export to Excel
An advantage I didn’t expect: The model picks up more than just spatial errors. It t a just spat a e o s tcatches some data input errors too!
P t ti l E FilPotential Errors File
If this option is checked, the files will add to the display as they aredisplay as they are created by the model.
P t ti l E FilPotential Errors File
2,247 Records
P t ti l E FilAdd columns to track Reason Result Action
Potential Errors FileAdd columns to track Reason, Result, Action
G di EGeocoding ErrorsAlong centerlines
G di EGeocoding ErrorsWithin Parcels
20362
20658
G di EGeocoding Errors
Suffix difference—81Don’t dismiss
digeocoding errors
Could be true errorsCould be true errors
S ti l ESpatial Errors
Incorrectly split street segments
Once completed…
K EKnown Errors
Will appear in Potential Errors every timeevery timeCopy/Paste features into Known_Errors.shp_ p
K EKnown Errors
Use the model to take them out of results
R ltResults
Of the 600,000-700,000 Registered VotersResearch about 3,0001,200 out of Precinct (Same District)770 out of District214 L tt S t214 Letters Sent12 Calls Back0 Previous Contests Could Have Been Swung0 Previous Contests Could Have Been Swung
N tNext
Use Geocoding Service with ArcGIS OnlineRun Model on Inactive/Deceased VotersShare the Model with Other Counties
Q ti ?Questions?