Introduction to Geographic Information Systems Spring 2013 (INF 385T-28437)

Dr. David ArcturLecturer, Research Fellow

University of Texas at Austin

Lectures 8 & 9Feb 28, 2013

8 - Spatial Analysis9 - Geocoding

Geocoding Outline (Tutorial Ch.7) Geocoding overview Linear (street) geocoding Problems and solutions Street map sources Polygon geocoding Geocoding in ArcGIS Useful Web sites

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GEOCODING OVERVIEWLecture 9

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Geocoding Process of creating geometric

representations for locations (e.g., points) from descriptions of locations (e.g., street addresses)

Uses a computer program that employs code tables to standardize address components called a geocoding engine

Two ways to geocode Batch geocoding—attempts to match all

addresses Interactive rematching—sophisticated user

interface to match addresses4INF385T(28437) – Spring 2013 – Lecture 9

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Geocoding examples City’s economic development department

maps technology businesses by street addresses to see technology-rich areas in a city

County health director maps personal care and nursing homes and compares them to elderly population by neighborhood

Business maps store locations and compares to competitor locations

Emergency dispatch operators geocode an address to determine who should respond to an emergency call

Others?INF385T(28437) – Spring 2013 – Lecture 9

Geocoding files Tabular data (text or dbase)

Street addresses ZIP codes Latitude and longitude

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Geocoding files Geographic data

Street centerlines ZIP code polygons

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Other geocoding files Lines

Railroads, rivers Polylines

Parcels, census blocks, tracts, MCD/CCDs, places, counties, etc.

Points Landmarks such as churches, schools, and

other cultural features represented as TIGER as points

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LINEAR (STREET) GEOCODING

Lecture 9

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Linear geocoding (streets) Urban street maps

Four street address numbers ranging from low to high for each side of a street segment

100 198

101 199

Oak Street

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Geocoding stepsOriginal address: 125 East Oak Street 15213

Address parsed: |125|East|Oak|Street| 15213

Abbreviations standardized: |125|E|Oak|St|15213

Elements assigned to match keys:[HN]:125 [SN]:Oak[ST]:St [SD]:E [ZP]:15213

Index values calculated: [HN]:125 [SN]:Oak(Soundex # ) [ST]:St [SD]:E [ZP]:15213 (Index #)

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Geocoding steps

From To Street Type Side Parity Direction Street_2 98 Oak St R E W 43441 99 Oak St L O W 4345100 198 Oak St R E E 4346101 199 Oak St L O E 4357

Candidates identified: 125 East Oak Street15213

Candidates scored and filtered:

From To Street Type Side Parity Direction Street_100 198 Oak St R E E 4346101 199 Oak St L O E 4357

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Geocoding steps

From To Street Type Side Parity Direction Street_101 199 Oak St L O E 4357

Best candidate matched

Oak StPi

ne A

v100101

198199

123

21

9899

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Number 123 Oak St E, Apt. 2, Pittsburgh, PA 15213Street name 123 Oak St E, Apt. 2, Pittsburgh, PA 15213Street type 123 Oak St E, Apt. 2, Pittsburgh, PA 15213Direction, suffix 123 Oak St E, Apt. 2, Pittsburgh, PA 15213Direction, prefix 123 E Oak St, Apt. 2, Pittsburgh, PA

15213Unit number 123 Oak St E, Apt. 2, Pittsburgh, PA 15213Zone, city 123 Oak St E, Apt. 2, Pittsburgh, PA 15213Zone, ZIP code 123 Oak St E, Apt. 2, Pittsburgh, PA 15213

Items for single number street address:Address Unit City ZIP Code 123 Oak St E Apt. 2 Pittsburgh 15213

Address components

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PROBLEMS AND SOLUTIONSLecture 9

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Possible problems Variations in street names

Fifth Avenue, Fifth Ave., 5th AV Saw Mill Run Blvd, Route 51

Data entry errors Fidth Avenue Sawmill Run

Place Names White House, Heinz Field, Empire State Building

Intersections Fifth Avenue and Craig Street

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Possible problems Zones

100 Main ST 15101, 100 Main ST 16202 P.O. boxes

P.O. Box 125 Missing street (TIGER) information

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Solutions Clean data before geocoding Use postal address standards

Publication 28 of the U.S. Post Office (2000) Ultimate source on mailing address formats and

codes Provides standard street address formats Standards include house number, prefix

directional, street name, street suffix, common unit designator abbreviation for apartment, city, state abbreviation, five-digit ZIP code, ZIP+4 extension

Use Standard Intersection Connectors & | @INF385T(28437) – Spring 2013 – Lecture 9

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Solutions Use alias tables

Points of Interest (POI) databases; gazetteers

Assign house numbers in rural areas Purchase or build high quality maps

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Alias AddressWhite House 1600 Pennsylvania AvenueHeinz Field 100 Art Rooney Avenue Empire State Building 350 5th Ave

STREET MAP SOURCESLecture 9

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TIGER/Line files 2000 Census street centerlines

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Caution: source has changed

TIGER/Line files

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Caution: source has changed

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Commercial sources for maps GDT / ETAK / TeleAtlas TomTom.com

All the big pioneers of streetmaps are now TomTom

Esri StreetMap Premium for ArcGIS No more free streetmaps

MapBox.com (free & fee)

Others…?INF385T(28437) – Spring 2013 – Lecture 9

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OpenStreetMap.org (free open-source)

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POLYGON GEOCODINGLecture 9

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Polygon geocoding Suppose you wished to make a

choropleth map showing distribution of attendees at an event

Need to geocode data whose identifier is a polygon (e.g. ZIP code, city, or county) Create an aggregate table with a single record

for each unique polygon Count the records for each polygon Join table to corresponding polygon layer Symbolize with a choropleth map or

graduated point symbols 28INF385T(28437) – Spring 2013 – Lecture 9

Polygon geocoding (ZIP codes)

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Polygon geocoding (ZIP codes) Points created at ZIP code centroids

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Polygon geocoding (ZIP codes) Spatially join points to polygons to

make choropleth map

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Choropleth map result

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GEOCODING IN ARCGISLecture 9

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Create address locator ArcCatalog

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Choose address locator style Skeleton of the address locator Based on data tables and reference

layer

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Choose reference layer Streets, ZIP codes

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Address locator properties

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Geocode in ArcMap Add tabular data and streets layer Add address locator Geocode addresses View geocoding results Interactively rematch addresses

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Address rematching Investigate unmatched addresses

Generally requires expertise with knowledge of local streets

Compare street name in the attributes of streets table and address table

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Prepare log file Log file includes reasons why

addresses did not geocode Useful for future work on cleaning

addresses or repairing street maps

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Incorrect address Possible reason/solution490 Penn Avenue Missing ZIP code111 Hawksworth Spelled incorrectly900 Smallman Street TIGER street missing900 Lib Ave Spelled incorrectly

USEFUL WEBSITESLecture 9

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Useful Web sites http://www.usps.gov/ http://www.geocode.com/ (TomTom fee

service) http://batchgeo.com/ http://www.mapquest.com http://maps.google.com http://www.bing.com/maps/ http://www.zipinfo.com http://zipskinny.com/ Others?

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Geocoding Summary Geocoding overview Linear (street) geocoding Problems and solutions Street map sources Polygon geocoding Geocoding in ArcView Useful Web sites

Complete Assignment 7-1 (7-2 optional)

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