The American Civil Liberties Union has sued to stop Baltimore police from launching a sweeping “eye in the sky” surveillance program. The initiative, operated by a company called Persistent Surveillance Systems (PSS), would send planes flying over Baltimore at least 40 hours a week as they almost continuously collect wide-angle photos of the city. If not blocked, a pilot program is expected to begin later this year.

The ACLU complaint, filed on behalf of Baltimore activists, describes the “Aerial Investigation Research” plan as “the most wide-reaching surveillance dragnet ever employed in an American city.” It follows an earlier, secret aerial surveillance program that was revealed in 2016. While that operation (also run by PSS) was shut down, Baltimore officials voted earlier this month to launch a more public version, starting with a privately funded 180-day test run.

The ACLU argues that the plan didn’t receive a fair hearing during the novel coronavirus lockdown and that it violates Fourth and First Amendment rights by infringing on privacy rights. It’s asking a judge to permanently prevent the program from launching.

Proponents argue that the system can help police investigate violent crimes, including murder, and the current plan includes grants to let researchers study its effect on the city’s crime rate. However, the ACLU calls it a “virtual, visual time machine whose grasp no person can escape.” The images aren’t high-resolution enough to visually identify a person on the ground, but hours of footage could let officers “roll back the tape” to catch an anonymous person leaving a known address, and the footage could be cross-referenced with other forms of surveillance.

Police in Baltimore have a long history of using high-tech surveillance methods, including controversial “stingray” phone trackers. In 2016, the ACLU published evidence that they used the social media tracking tool Geofeedia to arrest protestors after the death of Freddie Gray. The aerial surveillance program grows out of a military drone photography system known as Gorgon Stare.