Geographic Information Systems (GIS) Services Frequently Asked Questions:
How do I geocode addresses in ArcMap?
What is Geocoding?
“The process of finding the location of a street address on a map. The location
can be an x,y coordinate or a feature such as a street segment, postal delivery
location, or building. In GIS, geocoding requires a reference dataset that contains
address attributes for the geographic features in the area of interest”
(Source: GIS Dictionary - ESRI
Support,
Accessed: July 1, 2005).
Is Geocoding a Necessary Step for Your Project?
The geocoding steps listed here are only necessary if you have many addresses to
geocode. If you only have a few, it might be easier to use a website that will
geocode the addresses for you. For a listing of some websites that provide geocoding,
see Resources for
Address Matching. You may also consider hiring a vendor to geocode the addresses
for you. The Census Bureau maintains
a webpage that lists some vendors who offer geocoding.
Instructions for Geocoding
Follow the below instructions to geocode addresses in ArcMap.
Click here to watch a demo of this process. Please Note:
Flash player plugin is required to view this demo.
These instructions are specific for UNC Chapel Hill affiliates. The data and the address locator referenced below are licensed to UNC Chapel Hill. Other patrons should inquire about alternatives.
- Create a table of the addresses to be geocoded in Excel. You'll want four columns: Address, City, State, and Zip- you may also want another column, such as a Name or ID column.
The above column headings are used throughout these instructions. If you choose to use different column headings, make sure they do not contain spaces (Street_Address rather than Street Address). If there are spaces in the column headings, the data cannot be added to ArcMap.
Here is an example of how the data should look:
| Address | City | State | Zip |
| 720 Franklin St. | Chapel Hill | NC | 27516 |
- In Excel, save the file as a tab delimited text file, and then open it in ArcMap.
Select File -> Save as. Provide a file name and choose "Text (Tab delimited)" from the "Save as type:" drop-down box at the bottom.
You will get a dialog box that says "filename.txt may contain features that are
not compatible with Text (Tab delimited). Do you want to keep the workbook in
this format?"
Click Yes.
- Close the file in Excel. When you attempt to close the file you will get
another dialog box, with the following message: "Do you want to save the changes you made to 'filename.txt'?"
Click No. You already did that in step 2.
- Open ArcMap.
- Add the filename.txt file to ArcMap just as you would spatial data, (File -> Add Data or use the Add Data button).
- After bringing the address table into ArcMap, open it and check it to make sure it came over ok.
- Add the street data:
Streetmap 04 is available on the campus network:
J:\isis.unc.edu\data\gis\esri\street_map\streetmap04\Streets\streets.sdc
-
Add an Address Locator:
An address locator "defines the process for translating nonspatial descriptions
of places, such as street addresses, into spatial data that can be displayed as
features on a map" (Source:
GIS Dictionary - ESRI Support,
Accessed July 1, 2005).
To add an Address Locator, use the Address Locator Manager:
From the drop-down menu in ArcMap, select Tools -> Geocoding ->
Address Locator Manager.
Click the "Add..." button to add the address locator, and navigate to:
J:\isis.unc.edu\data\gis\esri\street_map\streetmap04\Streets\
Select the StreetMap USA address locator and click "Add" (wait a second for the
address manager to load). After the StreetMap USA Address Locator is listed in
the Address Locator Manager, click Close.
-
Now that you've selected an address locator, you are ready to Geocode.
From the drop-down menu in ArcMap, select Tools -> Geocoding -> Geocode Addresses.
Select the StreetMap USA address locator to use, then click OK.
Geocode the addresses in the table you added.
Make sure the table is selected in the Address table: drop-down menu.
Make sure the Address Input Fields Match those below:
Street or Intersection: Address
City: City
State Abbreviation: State
Zip: Zip
- After the geocoding process is complete, a "Review/Rematch" window will be returned that contains a summary of the results. If you'd like, rematch any addresses that did not match interactively by clicking on the "Interactive Rematch" button. Alternatively, you could modify the geocoding options (change the default settings), and rematch automatically by selecting the "Match Automatically" button.
TIPS:
Be cautious when rematching your address data! An unmatched address is much better than an incorrectly matched address.
P.O. Box addresses will not geocode to a street location - the closest geocoding option for a P.O. Box is ZIP Code.
Geocoded locations may not be very accurate. They are approximations based on street data. At best, they are as accurate as the street data.
For full explanation of the geocoding process, see the following online resources:
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our Main Page, GIS Services
For more GIS assistance,
Please contact Amanda C.
Henley, GIS Librarian
amanda.henley@unc.edu
(919) 962-1151
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