How to Observe Police Surveillance at Protests - EFF Senior Investigative Researcher Dave Maass provides an overview of police surveillance technologies used at protests in the United States.
Slides: https://www.eff.org/document/slides-observing-police-surveillance-protests
Transcript: https://www.eff.org/document/transcript-observing-police-surveillance-protests-november-2020
Source: Electronic Frontier Foundation