GIS Tutorial 1 Lecture 7 Geocoding
Dec 17, 2015
GIS Tutorial 1
Lecture 7Geocoding
Outline Geocoding overview Linear (street) geocoding Problems and solutions Street map sources Polygon geocoding Geocoding in ArcCatalog & ArcMap Useful Web sites
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GEOCODING OVERVIEWLecture 7
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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 addresses
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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?
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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 7
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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 steps
Original address: 125 East Oak Street 15213Original address: 125 East Oak Street 15213
Address parced: |125|East|Oak|Street| 15213Address parced: |125|East|Oak|Street| 15213
Abbreviations standardized: |125|E|Oak|St|15213Abbreviations standardized: |125|E|Oak|St|15213
Elements assigned to match keys:[HN]:125 [SN]:Oak[ST]:St [SD]:E [ZP]:15213Elements 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 #)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 4344
1 99 Oak St L O W 4345
100 198 Oak St R E E 4346
101 199 Oak St L O E 4357
Candidates identified: 125 East Oak Street15213Candidates identified: 125 East Oak Street15213
Candidates scored and filtered:Candidates scored and filtered:
From To Street Type Side Parity Direction
Street_
100 198 Oak St R E E 4346
101 199 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 matchedBest candidate matched
Oak StPin
e A
v100
101
198
199123
2
1
98
99
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Number 123 Oak St E, Apt. 2, Pittsburgh, PA 15213
Street name 123 Oak St E, Apt. 2, Pittsburgh, PA 15213
Street type 123 Oak St E, Apt. 2, Pittsburgh, PA 15213
Direction, suffix 123 Oak St E, Apt. 2, Pittsburgh, PA 15213
Direction, prefix 123 E Oak St, Apt. 2, Pittsburgh, PA 15213
Unit number 123 Oak St E, Apt. 2, Pittsburgh, PA 15213
Zone, city 123 Oak St E, Apt. 2, Pittsburgh, PA 15213
Zone, 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 7
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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
& | @
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Solutions
Use alias tables
Assign house numbers in rural areas Purchase or build high quality maps (field
verification)
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Alias Address
White House 1600 Pennsylvania Avenue
Heinz Field 100 Art Rooney Avenue
Empire State Building 350 5th Ave
STREET MAP SOURCESLecture 7
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TIGER/Line files
2000 Census street centerlines
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TIGER/Line files
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TIGER/Line files
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Street Map USA
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GDT Dynamap/2000 U.S. street data
Small fee for individual ZIP code layers Map layers are the highest quality
street-map layers in terms of appearance, completeness, and accuracy
Maps include more than 14 million U.S. street segments and include postal boundaries, landmarks, water features, and other features
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POLYGON GEOCODINGLecture 7
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Polygon geocoding Method to map data whose identifier
is a polygon (e.g. ZIP code, city, parcel
identifier- ppn, 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
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TIGER: Polygon topology ZIP codes American Indian Reservation Alaska Nature Village Statistical Area Tribal Designated Statistical Area Tribal Jurisdiction Statistical Area Alaska Nature Regional Corp. FIPS State and County Codes MCD Place Census tract/block groups/blocks
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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 ARCCATALOGLecture 7
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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/solution
490 Penn Avenue Missing ZIP code
111 Hawksworth Spelled incorrectly
900 Smallman Street TIGER street missing
900 Lib Ave Spelled incorrectly
USEFUL WEBSITESLecture 7
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Useful Web sites http://www.usps.gov/ http://www.geocode.com/geocode.htm http://www.batchgeocode.com/ http://www.mapquest.com http://maps.google.com http://www.zipinfo.com http://zipskinny.com/
http://www.semaphorecorp.com/cgi/zp4.html
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Summary Geocoding overview Linear (street) geocoding Problems and solutions Street map sources Polygon geocoding Geocoding in ArcView Useful Web sites
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