When it comes to geocoding, there are many options out there to quickly match addresses to a point on a map. Google Maps is the obvious choice but for GIS professionals, the ESRI Worldwide Geocode Service is the way to go.
Unless … you want to create your own address matching service. It’s easier than you might think but there are pros and cons to both options. In our web-based app, SchoolSite Locator, we allow our customers the option of using an address locator based or their county’s GIS data or using the one provided by Esri. We often guide our clients as to which option would best suit not only their needs but which might be best for where they are located. One of the biggest factors in determining success when address matching is how quickly the landscape is changing. Perhaps new housing developments going up every six months or maybe the area relatively built out with little to no available land. Here are some quick tips to help guide your decision…
ESRI Worldwide Geocode Service:
This option consists of professionally maintained and updated street and parcel data provided free of charge by ESRI when temporarily address matching. If you want to store the results, it does cost credits to batch geocode and save the results but when using it for a quick lookup in a web app, it is 100% free. Keep in mind that brand new developments (and other areas of recent change) might not be available or updated in a timely fashion. Esri controls the update schedule and it different for each area. More rural areas might not get updated as often as cities for example. When you find errors, which you will, your only recourse is to report them to Esri and wait for an update. Street base maps are rendered with incredible detail at many different scales, far better than what you can do with a street or parcel layer yourself, and make a web map look very professional.
Using the Esri Worldwide Geocoding service is recommended for districts who cannot obtain any GIS street data for their area, who want to save time and money, and/or for those who are mostly built out and do not foresee many new streets being developed or housing built.
Custom address locator services:
First off, in order to create your own address locator service you need to have access to ArcGIS Enterprise. Davis Demographics uses ArcGIS Enterprise to host geocode services for our clients but if you have your own server running, you can also publish your own address locators as a service.
You also need to get access to a copy of street, parcel, or address point data. This is usually provided by your county as GIS data. Once you get a copy, you must either update it yourself as you become aware of new housing developments and streets that are created, or you must check back with your county a few times a year to get a new copy as they make changes on their end. Some counties are more proactive in updating and making the data available than others so your experience may vary. Maintaining address data can involve adding new streets or correcting errors of existing streets as they are discovered. You will also be responsible for creating your own address locator and setting the parameters such as identifying the fields you want to use from the data and setting spelling sensitivity and more.
It might sound like a bit of work up front, but once you put in the time and effort you then have the ability to geocode to 99.99% accuracy knowing that your data is as up-to-date as possible. You can choose to geocode to street centerlines, parcels, or a combination of both using a composite locator as well. And when you find missing streets or errors with existing streets, they can be fixed and updated in your app in a matter of minutes.
Using a custom address locator service is recommended for districts that are seeing lots of new development and growth in their communities. It also provides for more fine-grained control over how the address matching process works.
Remember: NO street data is 100% perfect. The only sure-fire way to tell which type of street data will provide the best results would be to geocode your student file against each type of GIS street data to see which one gives you the best match score. If you can match thousands of records against Esri’s Worldwide Geocode Service with 95% or better accuracy then maybe it’s the right choice for you. However, if you find a lot of addresses are unmatched or have been matched to street names or to zip codes and not to exact rooftops then you will want to look for a better data source and consider making your own geocode service.
If you need more information or want to discuss your web mapping or address matching needs, get in touch with us.
