Open Census Geocoding
Problem Statement:
The US Census' TIGER/Line Shapefiles represent over 3,200 individual files with cartographical information for every county in every state of the US. The files are very large, and require a certain level of technical expertise to extract the embedded information out of the shapefile format the TIGER files are distributed in.
OpenPHI has pre-processed one of the most important files of the TIGER dataset for each county. We now distribute these files for free in a database-friendly (SQL) format for easy integration with your own systems and applications.
The freely downloadable, pre-processed Census TIGER files for each county in every state are already available. Here you can download pre-processed EDGES files at no cost.
Download the "Open Census Geocoding: Setup your own Geocoding Server" white paper for more details.
Summary
The white paper will:
- Explain the basic structure of the US Census TIGER shapefiles
- Help you use these free files to setup your own free geocoding server for US-based addresses using the TIGER shapefiles. This server will allow you to perform the geocoding process locally, without calling any external geocoding service.
As per Wikipedia: "Geocoding" is the process of finding associated geographic coordinates (often expressed as latitude and longitude) from other geographic data, such as street addresses, or zip codes (postal codes). With geographic coordinates the features can be mapped and entered into Geographic Information Systems, or the coordinates can be embedded into media such as digital photographs via geotagging. "Reverse geocoding" is the opposite: finding an associated textual location such as a street address, from geographic coordinates. A geocoder is a piece of software or a (web) service that helps in this process.
Rationale
You may ask yourself "Why would I need to setup my own geocoding server?" There are many web-based geocoding services already available. But these services:
- Have some form of registration requirement => infringing on your privacy and potentially analyzing your usage patterns
- Impose usage fees past a low number of free queries => this impacts your operating budget
- Have restrictive terms of use => limiting your ability to use the resulting geocoded data as you please
- May not use the latest Census data files => providing you with inaccurate information
- Do not disclose their methodology => you are unable to learn from their implementation algorithms
Having the ability to geocode your own (personal / institutional / business) data without external interference opens the door to unlimited new opportunities to develop unique and powerful geography-enabled applications.
Short of paying a lot of money to license a commercial vendor's geographical datasets, the US Census TIGER shapefiles are one of your best free sources of high-quality geographical data for the US.
Commercial Services
Please notice that this is a very hands-on process that requires a significant level of UNIX-level expertise. OpenPHI offers the following commercial services for a fee:
- data conversion from TIGER shapefiles to other formats: ASCII, CSV, XML
- creation of custom shapefiles for any county and state
- custom software development
- consulting services
We can also geocode (Lat/Long) each and every possible address in each address range for each county. The US Census' TIGER 2009 shapefiles include each possible address in most cities and towns of the country. For example, the TIGER files include all the possible addresses in the range of "100 - 119 Oak Ave, Anytown, FL"
OpenPHI can process each TIGER file to extract the Latitude and Longitude for each individual address in that range. That is, "100 Oak Ave" has a pair of Lat / Long values. And "102 Oak Ave" will have a separate, different pair of Lat / Long values.
Disclaimer
Neither this website nor its associated files are endorsed by the U.S. Census Bureau.
TIGER and TIGER/Line are registered trademarks of the U.S. Census Bureau; ZCTA is also a trademark of the U.S. Census Bureau.
"By law, Title 17 U.S.C., Section 105, copyright protection is not available for any work of the United States Government. Thus, the Government is precluded from copyrighting its publications. Consequently, you are free to reproduce census materials as you see fit. The U.S. Census Bureau requests that any repackaging of the TIGER/Line Shapefile data (and documentation) and other files accompanying it for distribution include a conspicuously placed statement to this effect on the product's cover, the first page of the website, or elsewhere of comparable visibility."
