However bad you think it is it's safe to assume it's way worse. Radar (not visible light) algorithms that I wasn't privy to the details of could track hundreds of vehicles and dismounts circa 2010. Our "test data" was a recording taken over a Washington DC suburb (so not downtown Manhattan, but still thousands of cars, hundreds upon hundreds of pedestrians joggers, cyclists, etc.) This was done with a single bajillion dollar military radar. This was a production system and not even the latest and greatest at the time. Imagine what far more far cheaper, albeit with worse receiver hardware drones can do in the visible spectrum.