Identifying Misplaced Voters Using a Voter-Precinct ... · Identifying Misplaced Voters Using a VoterUsing a Voter-Precinct Verification Model Steve Demers, Sacramento County Voter

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?