Think you live in a town so small it’s not even on the map?
Thanks to a combination of advanced satellite technology, geospatial mapping tools and real people pounding the pavement, even the most remote hamlets and hidden homes in the United States have been put on a map by the U.S. Census Bureau.
The Census Bureau can verify housing units on a single block within two minutes by computer versus the two hours it previously took to do it on foot.
Since the first census in 1790, the Census Bureau has completed a count of every person living in the United States and its territories every 10 years by literally walking (or riding on horseback) on every single road and every single block in the country. In 2010, that was 11.2 million blocks — or 67 million miles traveled.
“The number of miles we walked (for the last Census was) astronomical,” said Robert Colosi, special assistant to the chief of the Decennial Statistical Studies Division. “We’re not going to do that in 2020.”
Times and technology have changed and nearly 70% of addresses in the country have already been verified without anyone having to leave their office.
The Census Bureau has created a software application known as BARCA or Block Assessment Research Classification Application. The program compares satellite images of the United States over time, allowing Census Bureau employees to spot new housing developments, changes in existing homes, or other housing units that did not exist before.
Result: The Census Bureau can verify housing units on a single block within two minutes by computer versus the two hours it previously took to do it on foot.
The Census Bureau’s Master Address File (MAF) provides the correct addresses for mailing census questionnaires — and enables the bureau to track homes that may require a follow-up visit by a census taker to help occupants complete the form.
All of the nation’s 11,155,486 blocks have already been reviewed.
Geospatial technology has improved or corrected 75 million addresses, and 5.3 million new addresses have been added over the last decade, according to the 2020 Census Program Management Review.
This “in-office address canvassing operation” is now the primary way the Census Bureau updates addresses. As a result, only 34.9% of the nation’s streets will be canvassed in person, this summer.
That means only 35,000 census takers will be needed, compared to 150,000 in 2010, according to John Pollicino, team lead of the Census Bureau’s Geography Division’s Spatial Update Branch.
At the Census Bureau’s National Processing Center in Jeffersonville, Ind., a team of employees reviews current satellite imagery and compares them to images from 2010.
They label blocks as “passive, active or cloudy”. Passive blocks show no change in housing or new addresses since 2010 while active ones show notable changes and require further office or in-person review. Cloudy literally signifies an image is obscured by clouds.
“The imagery is updated so frequently that sometimes we have bad imagery,” Pollicino says. “Let’s say a storm happens to be passing through; all we get is clouds. So now, we have to review it again.”
The MAF is the Census Bureau’s “crown jewel,” according to Colosi of the Decennial Statistical Studies Division. Much of the information is collected by the Census Bureau but the file also includes data contributed by the US Postal Service and local governments through special partnerships designed to ensure the most up-to-date list of housing units across the country.
The Census Bureau only accepts data from these partners but it does not share its list with them.
“This information is used to invite people to respond to the census,” said Census Bureau Chief of Geography Division Deirdre Dalpiaz Bishop. “So, when we conduct the mailing of our letters and our postcards asking people to respond to the census, it’s using the Geography Division's Master Address File.”
The Census Bureau address team uses specific triggers to determine whether to recheck blocks or areas.
“For example, if the Post Office says that there’s a new address in that block, that would trigger that block, and we would review it again using aerial imagery and see if we can see the new housing unit, like a rooftop, for instance,” Colosi said.
The Census Bureau also created TIGER, the Topologically Integrated Geographic Encoding and Referencing database.
TIGER transformed paper maps into an electronic system and is the underpinning of most of the mapping technology we use today.
This same mapping system will guide canvassers and census takers in the field when the 2020 Census begins in the spring.
"The geospatial system as we know it really started back in the ‘80s and early ‘90s, and we’ve built on it since,” Bishop said. “Google Street View, Open Street Map, Bing – they used TIGER to build their foundation and they continue to use TIGER to update the features they have in their mapping databases.”
For address canvassing, the Census Bureau partners with a leading geospatial information organization, Digital Globe, and the National Geospatial-Intelligence Agency. They provide real-time satellite images of the country. The U.S. Department of Agriculture provides satellite images of more remote areas.
In 1790, some 650 assistants to the U.S. Marshals spent nine months visiting every home they could identify in the young nation.
They counted nearly 3.9 million people, according to the Census Bureau.
Unfortunately, many of the original records from early censuses were lost or destroyed when the British burned Washington, D.C., in the War of 1812, according to Census Bureau Chief Historian Sharon Tosi Lacey.
Now the Census Bureau is looking even further ahead.
“The next step,” said Pollicino, “is to use this data to inform or to (leverage) this operation and do a more automated version of it.”