Geocoding for Neighborhood Research
February 2016
What is Geocoding?
Geocoding uses a description of a location, most typically a postal address
or place name, to find geographic coordinates from spatial reference data
such as building polygons, land parcels, street addresses, postal codes, etc.
What Happened?
•
Geocoding used to be easy!
•
ESRI switched from unlimited geocoding to pay-per-search geocoding
•
Bulk geocoding became expensive for many users
Before:
•
Now:
Special thanks to Eric Burnstein for testing and reporting on current
geocoding options
What Options are Available?
We tested a number of geocoding services. The best option will depend on
the specific needs of the research project.
• U.S. Census Geocoder
• Smarty Streets
• ArcGIS Online
• Semaphore ZP4
• Texas A&M Geoservices
• SAS Proc Geocode
• Google/Bing/Mapquest API
• Local Geocoders (ie. Washington,
DC MAR geocoder)
Which is Best for Me?
To assess the geocoding options, first answer the following questions…
• How many addresses do I need to geocode?
• What is the quality of my address data?
• Are the addresses limited to one city? State? The entire U.S.?
• Are the addresses mostly in Metro areas? Rural areas?
• How precise do I need the final output?
• How much project money is budgeted for geocoding?
• What is the end-goal (appending Census data, mapping for the web, etc.)?
Choosing a Geocoder
Are the
addresses
all local?
No
Over or under
1,000 records?
Under
Census
Geocoder
No
SAS Proc
Geocode
Over
Yes
Does the
project have
budget for
Geocoding?
Local
Geocoder
Yes
Texas A&M
Geoservices
Standard
Need to find
unmatched
addresses?
Desired
accuracy of
results
High
ArcGIS Online
Yes
ArcGIS Online
Best use: Project with sufficient budget that requires high level of accuracy.
• Pros:
•
Most accurate option
•
Fast processing
• Cons:
•
Expensive and difficult credit system
•
Higher learning curve than alternatives
U.S. Census Geocoder
Best use: Project with a small number of addresses and a tight budget.
• Pros:
•
Completely free
•
Easy to use
• Cons:
•
Limited to 1,000 addresses
•
Lower accuracy than alternatives
SAS Proc Geocode
Best use: Project with a large number of addresses and a tight budget.
• Pros:
•
Free (inside UI)
•
Handles unlimited addresses
• Cons:
•
Basic knowledge of SAS required
•
Lower accuracy than alternatives
Texas A&M Geoservices
Best use: Project with sufficient budget that requires high level of accuracy
and limited time to set-up and learn ArcGIS online.
• Pros:
•
Easy to use
•
Reasonable cost
• Cons:
•
Slower than the alternatives
•
Not the cheapest or the most accurate
Local Geocoders
Best use: Project uses addresses for only one city.
• Pros:
•
Highly accurate
•
Usually free to use
• Cons:
•
Limited to a single city
•
Need to learn a new tool for each city
Google/Bing/Mapquest API
Best use: Project with good quality address data, no or low budget.
• Pros:
•
Can use Stata. R, and other tools
•
Many are already be familiar with
these services
• Cons:
•
Limited free queries per IP per day
•
Less transparent on quality of matches
•
Enterprise API key is expensive
Other Options (not generally recommended)
Semaphore ZP4
Hybrid Geocoding Approaches
50,000
addresses
10,000
unsuccessful
geocodes
40,000
successful
geocodes
45,000
successful
geocodes
5,000
successful
geocodes
Questions?
Please ask now or email me!
[email protected]
Thank You!