Geocoding in ArcGIS

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ArcGIS
Lecture 2:
Output
Import data
Geocode
Outline
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Output- Presentation layouts & export formats

Importing- Spatial & attribute data

Geocode- Address matching & polygon method
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Lecture 2
OutputPresentation layouts & export formats
Map layout elements
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Main map size and location
Map title and subtitle
 what, where, and when
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Legend
 No need to label it Legend. Everyone will know
what it is (this eliminates “chart junk”)
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Data sources
Graphic scale
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Layout- Preview of Print to Paper or to an Image File
Layout View Icon
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Map layout elements
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North arrow
Rectangular boundary (neatline)
Other elements
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Inset maps
Data tables
Charts
Additional text
Photographs
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Layout example
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Layout example
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Fonts
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Style
 Simple and legible
 Formal or informal
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Number of fonts
Placement
Halos
 Contrasts background
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Bad layout
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Good layout
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Multiple maps on layout
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To add a data frame:
Select Insert> Data Frame
Example of 2 data frames:
2 thematic maps
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Multiple maps on layout

2 maps & 1 layout:
 Same size
 Same scale
 Subtitles (optional)
From Layout View:
-After the first map is completed,
Select Insert> Data Frame
-Select File> Add Data> select
desired data layer (The
select layer opens into the
new data frame)
-Move the data frame to an
open space
-Click and Drag the lower right
corner (grab handle) to resize
the data frame
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Export options from layout
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Raster
 .BMP, .TIF, .JPG
 Size/Resolution
 Color options
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Vector
 Enhanced Metafile (.emf), Encapsulated PostScript (.eps),
Adobe Illustrator (.ai)
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Web
 .JPG, .PDF, KML
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Export map
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Click data or layout view
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Export map
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File> Export Map
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Export options
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Exported map to Image file (.jpg)
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Exported map to Image file (.pdf)
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Lecture 2
Importing- Spatial & attribute data
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GIS data sources

Spatial data (shapefiles)
 U.S. Federal Government: data.gov
 U.S. Census Bureau- TIGER files
 Many web sources- at a cost & some free
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Attribute data (xls or dbf)
 U.S. Census Bureau- American Factfinder2
 Many web sources NEO CANDO local data
 Ohio Department of Health
 Many other web sources
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GIS data sources
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US government: TIGER files data.gov
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GIS data sources
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Census Bureau TIGER files:
http://www.census.gov/geo/maps-data/data/tiger.html
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GIS data sources
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Census Bureau attribute data: American Factfinder2
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Lecture 2
Geocode- Address matching & polygon method
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Geocoding

Process of creating geometric
representations for locations (e.g., points)
from descriptions of geographic locations
(e.g., street addresses) for display on a
map.
 Simply stated: Geocoding creates points
on a map from location descriptions
Geocoding Examples
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Sherwin - Williams maps their chemical coating
facilities and compares to competitor locations to
access its market penetration and additional market
areas.
A day care facility, maps schools and compares
them to population aged 5 to 11 years by census
block group in Cleveland to determine a possible
new day care location.
Locate NEOMED participating doctor’s offices by
street address and generate a demographic and
amenity based area profile.
Using MapQuest or Google Maps to geographically
locate an address
What is required to geocode?
1. Target attribute table:


Table to geocode may be an
Excel spreadsheet, dBase,
Access, or ASCII file (Word
doc)
The target table is the
attribute table to spatially
locate on a map
2. Reference database:


Data layer that will be used
to match the attribute data
In this example, the search
table is the US Census
TIGER street centerline file
Two methods of geocoding

Linear (Interpolation)- places point along street centerline:
Target database
Reference database
1201
1225 Main St.
1200

1299
Main St
1300
Polygon- places point at centroid (weighted center) of
polygon:Target database
Reference db: Parcel/ property
1225 Main St
1225 Main St
Main St.
Linear (interpolation) geocoding
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To locate the address 123 Oak St, Pittsburgh, PA 15213
In the reference database, candidates are located for
city or zip code, then the street name, street type, street
prefix, and finally the appropriate street address range
Details of a street centerline road segment are shown
below. Four street address numbers ranging from low
to high for each side of a street segment:
100
101
Oak Street
198
199
Linear geocoding steps
Original address: 123 East Oak Street 15213
Address parced: |123|East|Oak|Street| 15213
Abbreviations standardized: |123|E|Oak|St|15213
Elements assigned to match keys:
[HN]:123 [SN]:Oak[ST]:St [SD]:E [ZP]:15213
Linear geocoding steps
Candidates identified: 123 East Oak Street 15213
Candidates scored and filtered:
Linear geocoding steps
Best candidate matched
The address number is interpolated along the correct side of the street and
assigned x,y coordinates. The address record can then be displayed on the map.
Oak St
98
100
198
1
99
101
199
Pine Av
2
123
Polygon geocoding
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
Polygon geocoding matches one field value from the target
database to an exact match in the reference database.
Once the match is found, a point symbol is located at the
centroid of the polygon.
Target database
1225 Main St
Reference db: Parcel/ property
1225 Main St
Main St.
Geocoded point locations
using both methods
Possible geocoding issues

Variations in street names
 Fifth Avenue, Fifth Ave., 5th AV
 Saw Mill Run Blvd, Route 51

Data entry errors
 Misspelling- Fidth Avenue should be Fifth Avenue
 Misspelling- Sawmill Run should be Saw Mill Run
 Incorrect house number- 100 Main St should be 1000
Main St
 Incorrect Street type- 2021 Lorain Rd should be 2021
Lorain Ave
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Place Names
 Missing address- White House, Heinz Field, Empire State
Building
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Intersections
 Fifth Avenue and Craig Street
Possible geocoding issues
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Incorrect Zones (zip code)
 100 Main St, 15101 should be 100 Main St, 16202

P.O. boxes instead of street address
 P.O. Box 125
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Errors in the reference database
 Outdated- missing new street (TIGER)
information
 Street name changes
 Missing address ranges or gaps in address
ranges
 Zip code changes or incorrect zip codes
Possible solutions

Clean data before geocoding
 Run data through address standardizing software
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Use postal address standards
 Publication 28 of the U.S. Post Office (2012)

Ultimate source on mailing address formats and codes
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Provides standard street address formats

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Standards include house number, prefix directional,
street name, street suffix, common unit designator
abbreviation for apartment, city, state abbreviation, fivedigit ZIP code, ZIP+4 extension
Use Standard Intersection Connectors
 &|@
Possible solutions
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Use alias tables
Purchase or build high quality reference
maps (field verification)
Geocoding in ArcGIS
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Part A- Objective- Geocoding Using the Polygon method:
The goal is to display the locations of registered voters in a
small area in or near Cleveland’s Ward 18 using an attribute
database file (dBase) that contains a field of registered voter
addresses.
The registered voter geographic locations will be displayed
by matching its address field values to the address field
values of the parcel file.
This GIS process is called single-field geocoding in ArcGIS.
Geocoding in ArcGIS
Step 1- Determine the fields to match from the table to geocode
and reference table.
Open the voters.dbf and parcels.shp
Examine the attribute tables of the dBase file of voters and the
parcels to find the matching fields:
Geocoding in ArcGIS
Step 2- Create the address locator file. The address locator file
defines the geocoding style (polygon or address matching method)
and the file to be used as the reference file as well as other
characteristics such as the fields to match.
Select the ArcToolbox icon.
Select Geocoding Tools
Double-click Create Address Locator
Geocoding in ArcGIS
The Create Address Locator window
appears:
Click on the Address Locator folder
From the pop-up menu,
Select the address locator styleGeneral- Single Field
Click “OK”
Why select General- Single Field?
The goal is to match an address field value
from the table (voters) to geocode to a
“single field” value of the reference table
(parcels)
Geocoding in ArcGIS
Click on the Reference Data folder. Navigate to
h:\ArcGIS_1_workshop\Data and select parcels.shp and
click “Add.”
Click on the words “Alias Table” under Role.
A drop-down window will appear.
Select Primary Table to assign the table’s role.
This will allow you to indicate the field that will be the
match field from the reference file, parcels, in the Field
Map box area.
The field map options appear. Select the options shown
below.
On the row “*KeyField” click on <None> under Alias
Name. A drop-down window appears. Select
“ADDRESS”
“ADDRESS” indicates the field that will be the
matched field from the reference file, parcels.
Select OK
Geocoding in ArcGIS
The new address locator file, parcels_CreateAddressLocator, is created with the
parameters specified.
Note: When creating the address locator in ArcCatalog, additional parameters may also
be set such as spelling sensitivity, minimum match score, side offset distance from
street, and end offset distance from street end nodes:
End offset
Side offset
Geocoding in ArcGIS
Why is the side offset & end inset important?
Ward 1
Ward 2
50 feet side offset & 3% end inset
Ward 2
10 feet side offset & 15% end inset
Geocoding in ArcGIS
Step 3- Geocode the voter database file using the address locator file.
From Arctoolbox, geocode the voter database (dBase) table to the parcel polygon layer
matching addresses from the two tables:
In ArcToolbox, select Geocoding Tools
and then double-click “Geocode
Addresses”
Geocoding in ArcGIS
From the Geocode Addresses window:
Click on the folder icon next to Input Table
and navigate to and select voters.dbf from
your Data Folder on your H:/ Drive.
Click on the folder icon next to Input
Address Locator and select
Parcel_Address_Locator from your Data
Folder on your H: drive
When the Input Address Fields table
populates, click on the word “None” under
Alias Name and select Address_ST
Click on the folder next to Output Feature
Class, navigate to your Works Created
Folder and name the file: voters_geoc.shp
Click OK
Geocoding in ArcGIS
After selecting OK to geocode, along the bottom right
of your screen you will see a scrolling set of words,
“Geocode Addresses” to indicate that ArcGIS is
presently working on geocoding. .
If the geocoding process is successful, a box will
appear with a green check mark with the words
“geocoding successful”.
Geocoding in ArcGIS
Step 4- Display the geocoded voter point locations
In ArcMap, Add the parcel shapefile and voters_geoc data layers.
The voters should now display on your map with the parcels:
Geocoding in ArcGIS

Part B- Objective- Geocoding Using the linear
(interpolaton) method:



The goal is to display the locations of voter polling
locations in Cleveland using an attribute database file
(dBase) that contains a field of polling addresses.
The polling geographic locations will be displayed by
matching its address field values to the address field
values of the street centerline file.
This geocoding process uses US Address–Dual Range
in ArcGIS.
Geocoding in ArcGIS
Step 1- Determine the fields to match from the table to geocode
and reference table.
Open the voters.dbf and streets2000.shp
Examine the attribute tables of the dBase file of voters and the
streets to find the matching fields:
Geocoding in ArcGIS
Step 2- Create the address locator file. The address locator file
defines the geocoding style (polygon or address matching method)
and the file to be used as the reference file as well as other
characteristics such as the fields to match.
Select the ArcToolbox icon.
Select Geocoding Tools
Double-click Create Address Locator
Geocoding in ArcGIS
The Create Address Locator window
appears:
Click on the Address Locator folder
From the pop-up menu,
Select the address locator styleUS Address – Dual Ranges
Click “OK”
Why select US Address – Dual Ranges?
The goal is to match address field values
from the table to geocode (voters) to
“multiple field” values of the reference
table (street centerline file)
Geocoding in ArcGIS
For Reference Data select street2000.shp from
your H:/ Drive Data folder.
In the Reference Data Table change the “Role” to
“Primary Table” (this may already be done).
You may also notice that many of the fields in
the Field Map area are auto-populated to their
correct alias names and that the error message
has cleared.
The * means that field must have a alias name
populated with the corresponding field from the
reference data
The Output Locator Name should be
street2000_CreateAddressLoca
Select OK
The address locator is created.
Geocoding in ArcGIS
Step 3- Geocode the voter database file using the address locator file.
From Arctoolbox, geocode the voter database (dBase) table to the street centerline layer
matching addresses from the two tables:
In ArcToolbox, select Geocoding Tools
and then double-click “Geocode
Addresses”
Geocoding in ArcGIS
From the Geocode Addresses window:
Click on the folder icon next to Input Table and
navigate to and select polling_loc.dbf from your
Data Folder on your H:/ Drive.
Click on the folder icon next to Input Address
Locator and select
street2000_CreateAddressLoca from your
Work_Created Folder on your H: Drive
When the Input Address Fields table populates, be
sure that the Alias Name values are Address for
Street and ZIPCode for ZIP
Click on the icon next to Output Feature Class,
navigate to your Works Created Folder and name
the file: Polling_locations.shp
Click OK
Geocoding in ArcGIS
Step 4- The polling locations display and review the
attribute table
The polling locations should display on your map with the streets.
Right click the polling locations in the TOC and select Open Attribute table.
The table displays and contains a field, Status, that represents whether
the record was or was not geocoded. If the status field has a value of “M”,
then the record did geocode and a point is seen on the map. If the status
field value is “U”, then the record did not geocode. See table below:
Geocoding in ArcGIS
To determine how many records geocoded, select the Select by Attributes
icon in the table:
The select by attributes window pops up:
From Method box, select Status
Select =
Type ‘M’
You will see the Query syntax in the
select * box
Select Apply
Note: M = matched, U = unmatched
Geocoding in ArcGIS
The results of how many records geocoded are highlighted in the
attribute table. How many records geocoded? How many records
were in the whole table? The answer is located at the bottom of the
table:
Various reasons for unmatched records: misspelling, address
missing from file, incorrect street type (i.e. Rd. vs Ave.), wrong
street number, etc.
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