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LA County Specific Locators and Matching Rules

Notethis is NOT a data download, it is a highly post, with downloads enabling GIS professionals with ESRI’s ArcGIS Software to embed enhanced geocoding rules into ESRI software for improving matching rates.

LA County currently is able to match over 99.5% of incoming addresses.  Part of this has to do with the high quality of the reference file that we manage through the Countywide Address Management System, but a large part of this success rate has to do with something that many people take for granted – the geocode matching algorithms.


Some of this is my memory from conversations with Peter Fonda-Bonardi so I will follow up with him to validate.  I spoke about our programs and history a little while ago at the 1st International Geocoding Conference: I’ve attached the presentation materials here: Using GIS to improve Addressing (.pdf file)

In the mid-1980’s, LA County hired Matt Jaro to design and build a fuzzy matching system to automate the matching of misspelled names (MediCal and MediCare patients that hand’t registered correctly and therefore the County wasn’t able to get reimbursement for health services rendered).  This has led to the recovery of millions of dollars in revenue for the County based upon their standalone version of the software running on a UNIX platform.

The outcome of this was a matching program called Automatch developed by MatchWare technologies (here’s an article written by Matt Jaro).  This software was then licensed by ESRI to improve its matching at the time.  Yes – LA County’s matcher is inside of ArcMap (but is being phased out starting with ArcGIS 10).

The team responsible for developing the tool, led by Wayne Bannister, Peter Fonda-Bonardi, Victor Chen, and Yoko Myers  of LA County’s Internal Services Department Urban Research Section, are intimately familiar with the complex mathematics and pattern rules that make up the matching systems, and have tweaked them to be especially accurate in dealing with the strange addresses in LA County.  Some examples include (these all exist!):

  • W Avenue Q
  • Avenue 23
  • The Old Road
  • Outer Traffic Circle
  • Los Coyotes Diagonal
  • Avenue of the Stars
Why?  Peter Fonda-Bonardi optimized the way street names are broken apart so that they could be recognized more effectively, so that strange names don’t “break” the rules for addresses.  His expertise and understanding of the County’s 30+ addressing and house number systems (yes there are that many) have played a major role in getting us to where we are today.
Where we are now
A couple of years ago we were able to work with ESRI to bring the pattern rules back into their software, which has improved the County’s ability to geocode difficult street names, and provide these both as geocoding files and services underpinning many of our applications.  So now we can leverage all of the expertise and work that Peter and Victor have put into the matcher within the general systems we use.

Download the Matching rules

All required files are in this zip file: LACounty_Locators.zip
How to use these matchers
NOTE: this is very technical, and I assume ability to unzip files, know where your ArcGIS is installed.  NOT for the faint of heart!

New Locators


Step 1: Unzip the files to the correct folders Make sure to back up your current folders first

The zip file has two folders in it that match two folders in your ArcGIS installation location.   Unzip folders, then copy the files in the zip file to the same folders in your ArcGIS Desktop Installation, in my case this was C:\Program Files\ArcGIS\Desktop10.0

  • All files in the Geocode  folder –> C:\Program Files\ArcGIS\Desktop10.0\Geocode
  • All files in the Locators folder –> C:\Program Files\ArcGIS\Desktop10.0\Locators
From this point forward you will find three new locators in your “Address Locator Style” list (see picture at right).
Step 2: Standardize your reference file
You  need to format your reference file (standardize it) using the same rules that you will use to match.  This is critical for success – otherwise the address matcher doesn’t know what to match!
The “Standardize Addresses” Tool is available under the “Geocoding Tools” in Arc Toolbox.  Open that tool.

Using the standardizer

There are five boxes:

  1. Input Address data – this is your reference data file (could be TIGER, etc)
  2. Input Address Fields.  You need to fill this out correctly.
    1. Add the FID or OBJECTID field – ArcMap needs a unique identifier.
    2. Add ALL of the fields that make up the address.  Sometimes this is one field (TIGER’s FULLNAME), but if you have multiple fields (PRETYPE, PREDIR, etc) you will need to add them all, and in the correct order.  The standardizer will concatenate them before splitting them according to LA Countys’ rules.  DO NOT include address number, zipcode, or city fields.
  3. Address Locator Style – By completing Step 1, you should see three new locators starting with “LA County” in this list.  You need to know the type of your data to select the correct one:
    1. LA County Points with Zone – this is for address points
    2. LA County Streets with Zone DIME – this is the most common format (TIGER is one – it invented this format).  If you have left and right house ranges (Look for 4 columns with address numbers in them).
    3. LA County Streets with Zone NICKEL – very uncommon (but LA County uses it) – each record is a single range (left or right side) – look for only 2 columns with address numbers)
  4. Output Address Fields – CLick on “Select All” then uncheck the HouseNum, HouseSuffix, and ZIP fields.  Generally these already exist as separate fields in your dataset – no need to output them again.
  5. Output Address Data – select where you want the file to be output.
Click “OK”  – you will see this process run, and a new file will be output, which includes a set of new fields optimized for the LA County locator.
Step 3: Create your address locator

Creating the Address Locator

From the ArcToolbox “Geocoding Tools” you can get the “Create Address Locator”

There are five boxes:

  1. Address Locator Style – same as #3 in the last step – it has to match the reference dataset
  2. Reference Data – select the output from the standardizer.
  3. Field Map When you selected the Reference Data, all of the fields should be filled in.
    1. You may see a blank next to the “*House Number”  or “House From Left” field name – you need to select the field or fields that contain that data in your reference file.
    2. You need to go to the bottom of the list and check the Zone fields – Make sure they are filled in with the correct Zone information (this could be zipcode but could also be a city).
    3. We generally create one locator for zipcode, one locator for legal city, and one locator for postal city (if your reference data has these fields) – then tie them together with a Composite Locator (which I won’t discuss here).
  4. Output address locator – this is the name and location of the address locator that you will use for geocoding.  Make sure that it shows the zone information (e.g. Points_Zip vs. Points_LegalCity) so you know what it contains.

Click OK – the address locator will be created.  Have fun geocoding!

Using GIS Data on this site

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GIS data available on this website is provided AS IS - please read the GIS Data Portal Terms of Use

Data Field Descriptions


GIS Source Information
Database Name:
Feature Class Name:
Feature Dataset Name (if applicable):
Reference Date: 2011
Accuracy: Other
Update Frequency: As Needed
Access Constraints:None

Contact Information
Steve Steinberg
Geographic Information Officer
County of Los Angeles
Internal Services Department
9150 E. Imperial Hwy, MS#3
33.916650, -118.132255
Downey, CA 90242
(562) 392-7126

10 comments to LA County Specific Locators and Matching Rules

  • Brock

    Hi, I used this locator to geocode many schools in LA county. It worked well; however, I did not realize until later that it assigned strange xy coordinates, which are very different from the geographic coordinates I have for other schools in my datasets. Is this how coordinates come out of this locator, or would something else be the cause? The problem is that these unknown coordinate units (for example: x 6440381.5, y 1831397.5) are in a dataset with regular geocoordinates (like x -118.15127, y 34.028671). So when I try to load the spreadsheet into ArcGIS and create an xy event layer, it does not work. I believe the different coordinate units/systems in the x and y variables are derailing Arc’s ability to display the points. So, if this locator returns different spatial units, WHAT are they? And can I TRANSFORM them to regular geocoordinates? Help!

  • […] to support the County’s specifically designed geocoders – please see the entry on LA County Specific Locators and Matching rules for more […]

  • jfaliti

    Thanks for the quick reply!

    Yes, I am using the County matching rules. It seems that in the past that it was not necessary to concatenate all of the address fields. Would this have become necessary at 10.0?

    I’ll try the concatenated method.



  • Are you using the County matching rules? One note – in order to standardize you first have to concatenate all of the address fields into a single address column.

  • jfaliti

    Hi Mark,

    It seems that the Standardize Addresses function is not working properly at ArcGIS 10.0.

    Numbered streets are not being parsed correctly and in some cases the standardized record omits the numbered street and the street type is used to populate the street name field.

    Any thoughts on this? In a comment above you mention a release of newer rules for 10.x, would these be available yet?



  • […] to support the County’s specifically designed geocoders – please see the entry on LA County Specific Locators and Matching rules for more […]

  • Glad you got it to work. Let me know if the rules help your geocoding rates!

  • Mark, I have to retract my previous comment. It is NOT necessary to rename the files. I followed the instructions again and everything worked.

  • Thanks Jake. I will also be releasing some specific rules that ESRI built for us for use with their new 10.0 geocoders …

  • Mark,

    Thank you for this posting, the Los Angeles geocoder it is quite useful. I have one comment to make regarding installation for use with 9.3.x and 10.x. The file extension, .lot, works as is with 9.3.x, however the files must be renamed to .loc, in order to work with 10.x.

    Jake Aalfs

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