If you've visited Baltimore at any point during 2016, there's a good chance your every movement was tracked by the city's newest high-tech surveillance program.

The city is filthy with police surveillance cameras, but until this week little was known about the Baltimore Police Department's latest and most controversial tool for watching residents and visitors: a small aircraft that circles the city on an almost continuous basis, recording the movements of cars, people and everything else.

That aerial surveillance technology is the subject of a fascinating feature story published by Bloomberg Businessweek on Tuesday. Among the most startling details in the piece: the same program now being used in Baltimore—and being pitched to other police departments in other major cities—was originally designed to catch insurgents planting roadside bombs during the occupation of Iraq.

This is how the War on Terror comes home to roost.

More than six months after the covert eye-in-the-sky program was launched, the city is still barely admitting that it exists. The Baltimore Police Department never asked the public for permission—or, heck, even told them it was happening.

The project is run by an Ohio-based company called Persistent Surveillance Systems and relies on a "sophisticated array of cameras" attached to the belly of a small Cessna aircraft, according to Bloomberg's Monte Reel. The cameras can capture an area of roughly 30 square miles (about one-third the size of Baltimore) at any given time and continuously transmit real-time images to a group of analysts on the ground. All the footage is saved on hard drives for an unknown length of time.

Police have used the cameras to track suspected criminals and investigate a wide variety of crimes—"from property thefts to shootings," they claim in the article—but the secret cameras have also been used to keep tabs on peaceful protestors, like those who stood outside the city's courthouse on June 23 when one of the police officers accused of killing Freddie Grey was acquitted on all charges.

"This is a big deal," says Jay Stanley, a senior policy analyst for the ACLU. "It continues to be stunning that American police forces feel that they can use deeply radical and controversial surveillance systems, which raise the most profound questions about our society and its values, without telling the public that will be subject to these technologies—the public they are supposed to be serving."

Even now that the program has been revealed by Bloomberg, the city still won't admit that it's happening. The police department refused to comment for the Bloomberg story and did not return calls from Reason.

Before Baltimore, Persistent Surveillance quietly conducted a nine-day trial with the Los Angeles County Sheriff's Department in 2012, flying surveillance planes over Compton. The people being watched—including Compton Mayor Aja Brown—weren't told about it until a year later, and they were rightfully outraged when they found out.

Residents of Baltimore should be equally outraged that this has happened without their consent or knowledge, though perhaps the city's long history of intrusive surveillance and abusive policing has numbed the response—being observed from the sky certainly beats getting kicked in the chest (literally), right?

Ross McNutt, founder of Persistent Surveillance, tells Bloomberg that he believes the aerial surveillance can help police departments reduce crime by as much as 20 percent, though he also admits that he has no actual data to support that claim. The usage of the planes in Baltimore seems like a trial run before the company tries to market the same program to other cities—McNutt says he's already approached police departments in 20 different jurisdictions.

This is actually the second time in less than a year that residents of Baltimore have found out they were subjected to secret aerial surveillance. In 2015, it was revealed that mysterious planes had circled the city for hours at a time during the violent protests that erupted across the city after Freddie Grey's death in police custody. The FBI later admitted that those planes were part of a fleet of surveillance planes used by federal law enforcement, but the AP reported that the FBI's fleet was not equipped for "bulk collection activities."

At the time, the ALCU noted the existence of Persistent Solutions and wondered if it was that company's technology at work. It wasn't, but only a few months later, the Baltimore Police Department allowed Persistent Surveillance to start making similar flights—without telling anyone it was happening or asking permission from city officials and the general public.

As the Bloomberg story makes clear, these flights are very much about bulk collection. Videos are saved on "massive hard drives" and can be accessed at a later date.

There would seem to be some major constitutional issues with police surveillance on such a massive scale, but decades of court rulings have given wide deference to cops' ability to observe and track anyone and everything—with human eyes or cameras, it doesn't seem to matter.

If cities can put surveillance cameras on every street corner, if police can use license plate scanners to identify and track vehicles even when they are merely sitting in their owners' driveways and if cops can fly over a fenced-in backyard to see if someone might be growing marijuana—well, at that point what Persistent Surveillance is doing might be a difference of degree but not of kind. McNutt's company is just taking the big picture, literally.

Still, this is the first time police have had the ability to surveil an entire city in such a broad way.

In the Bloomberg piece (and in a presentation McNutt gave to the ACLU, in an attempt to gain their approval for his technology—or at least to head-off a lawsuit from them), Persistent Surveillance argues that their technology is actually less intrusive than many forms of street-level surveillance because the resolution is too low to identify individual people. Rather, people are merely "pixelated dots."

Stanley says that's a hallow argument, since surveillance systems never stand in isolation. Those "pixelated dots can be followed forward and backward in time as they move around the city. Used in conjunction with street-level surveillance, these aerial observations have the potential to track almost anyone in the city.

"Baltimore, like some other cities, has a lot of ground based cameras, but those cameras do not cover every square inch of the city, and their feeds are not stitched together with an artificial intelligence agent that is capable of using them in a coordinated fashion to follow individuals around anywhere within a 30-square-mile area," Stanley says.

Despite claims by McNutt that this surveillance technology will only be used to help police solve "major crimes," there are already signs that mission creep is happening. Persistent Surveillance has used their cameras to track Black Lives Matter protestors who were not accused of any crimes after Baltimore police expressed concern about possible "disruptions."

Indeed, the whole project is an example of mission creep. McNutt's company was originally contracted by the U.S. military to help find and catch insurgents making roadside bombs in Iraq, but now the technology is being deployed on the home front—just like so many other leftovers from a decade-plus of war in the Middle East.