If you have a smartphone, you’re probably contributing to a massive coronavirus surveillance system.

And it’s revealing where Americans have — and haven’t — been practicing social distancing.

On Tuesday, a company called Unacast that collects and analyzes phone GPS location data launched a “Social Distancing Scoreboard” that grades, county by county, which residents are changing behavior at the urging of health officials. It uses the reduction in the total distance we travel as a rough index for whether we’re staying put at home.

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(The Washington Post)

Comparing the nation’s mass movements from March 20 to an average Friday, Washington, D.C., gets an A, while Wyoming as a whole earns an F.

How do they know that? Efforts to track public health during the coronavirus pandemic are a reminder of the many ways phones reveal our personal lives, both as individuals and in the aggregate. Unacast’s location data comes from games, shopping and utility apps that tens of millions of Americans have installed on their phones — information the company normally analyzes for retailers, real estate firms and marketers. It’s part of a shadowy world of location tracking that consumers often have little idea is going on.

It’s not alone. Google also collects and shares where we go. Long before the coronavirus, the Google Maps app has included a live read of how busy popular destinations are, based on location data. Facebook’s Instagram, too, lets you see other people who’ve recently shared updates from places. Both tools are useful for anyone who wants to practice social distancing and avoid spaces that are busy for a jog or fresh air during shelter-in-place orders.

There’s no evidence that the U.S. government is using phones to enforce stay-at-home orders or track patients. But privacy is often the first civil right on the chopping block when public health and national security are at risk. Getting the balance right is hard. South Korea has used an app to track tens of thousands of quarantined people whose phone would alert authorities if they left home.

The Washington Post reported last week that the U.S. government is in talks with Facebook, Google and other tech companies about using anonymous location data to combat the coronavirus, including tracking whether people are keeping at safe distances from one another. The data wouldn’t be held in some federal database; it would be managed by industry and health officials, who could query it for research.

Social distancing in the Washington, D.C., area by county on March 20, according Unacast. Blue means staying closer to home. (Unacast)

Unacast, a smaller start-up, assigns letter grades to counties and states based on how much residents have changed their movements on a specific date compared to what’s typical on that day of the week. If many people in an area used to commute daily to work but now are leaving the house only for visits to the grocery store, the data would show a big reduction in travel distance.

The Unacast maps are searchable and will be updated daily. On Monday, the New York Times posted GPS data from a firm called Descartes Labs for March 11 through 20.

Unacast assigned an A grade to places that show at least a 40 percent decrease in average distance traveled. On March 20, the first day in its database, the states as a whole that earned an A included Alaska, Massachusetts, Nevada and Vermont. Big reductions in movement are also visible in areas hit hard by the virus, such as New York City (a 57 percent change) and California’s Santa Clara county (a 54 percent change).

Unacast deemed anything less than a 10 percent change an F. Only Wyoming earned that grade.

Overall, Unacast gives the United States a B, for a 32 percent decline in average distance traveled.

Unacast’s scores, which haven’t been vetted by public health authorities or epidemiologists, don’t pick up on whether people are staying at least six feet apart, a central tenet of social distancing. But the company says it is exploring adding layers to its view, including a change in the number of locations visited.

Unacast chief executive Thomas Walle said he hopes the maps might help track compliance with stay-at-home orders and measure whether they’re effective.

“We can start to see and learn what states are getting this right,” he said. “Over weeks now, we can identify what are the states and counties that are putting measures in place, and see if the number of cases stabilizes or drops.”

On Monday, a different group of researchers used data from half a million public Instagram stories to identify the places around Italy where people are breaking quarantine orders. The researchers from a group called Ghost Data and a firm called Logo Grab used location data and image analyses. About 40 percent of Italians not following the stay-at-home rules were in the city, and 26 percent were spotted at the beach.

Social distancing by county in the Chicago area on March 20, according to Unacast. Blue means staying closer to home.

All of these surveillance studies raise a question: Do people realize they’re sharing data about their whereabouts for these purposes?

Privacy advocates worry data firms like Unacast can be dodgy because they’re gathering locations without real consent from people.

Walle said all of the apps that Unacast acquires location data from must let users know. But he declined to name any of the apps. And we know few people read the privacy policies on apps — the fine print where they disclose the many ways they use your location, such as selling it on to data firms.

“Everything here is on the aggregated level,” Walle said. “We can’t tell or disclose if any individual is staying at home or not.”

Following health experts’ guidance to “flatten the curve” by limiting contact with others keeps everyone safer. But if you don’t want your phone’s location showing up on a social distancing map — or in the hands of marketers — carefully vet the apps you have installed or just turn off the phone’s location services.

Unacast's county-by-county grades for social distancing in Texas on March 20. The blue color indicates more staying put.