It technically is! The ACLU has a model ordinance called CCOPS, which it encourages municipalities to pass (I got my own muni to pass a version of it last year), and it includes an expansive definition of "surveillance" that definitely includes tools that read public posts on social media.

Importantly, CCOPS doesn't forbid surveillance; it simply requires new instantiations of it to be approved at an open board meeting. Things like Dataminr would almost certainly pass.

As you say, expansive. As in: it expands the definition of surveillance in a way that isn't widely accepted.

Expansive means large, vast.

Not necessarily growing.

Not necessarily. I agree with that. But in American English usage it is distinct from your meaning, which is more aligned with "extensive". The first entry for "expansive" in my usage dictionary is "tending to expand". The main reason to choose the word is to communicate growth.

Well, I wrote the word, and I didn't mean "growing".

Better to say "ever-expanding" or "constantly-expanding" and be unambiguous.

It "technically is" if you redefine it to include it. In other words, it isn't.

Judging by the cops I see around chicago their main responsibility is reading tweets actually.

Or eating Portillos. Or napping in their cars.

Does surveillance need to be covert? Historically, if the police are observing you or your event specifically, that's surveillance.

I mostly agree with you, but there’s a difference between using a non-covert method of communication like telephone or SMS, and a social media post, which is designed to be relayed and amplified.

What legitimate reason would the police have for monitoring everything on social media that is protected by the Constitution?

That really depends on which police you're talking about, and one's views on the Constitution. State and local police have fairly broad powers, and I don't know much about California's laws, so I'm not in a position to judge this.

Why would they need a "legitimate reason"? They are people like any other people. Anyone has the right to read things on Twitter. Police officers are normal people, they don't have special rights or privileges and they don't have special restrictions or limitations. That is the foundation of policing by consent.

We are paying their salary. Why should they be spending time attempting to proactively police a group who is just exercising constitutionally protected right?

There is actual crime they could be investigating. Instead they are wasting resources on something that they shouldn't have anything to do with unless there is a threat of violence.

That said, if you put a classified advert in a newspaper and police read it,i wouldn't call it survelience, and that feels more similar to reading twitter posts.

I think the idea of no expectation of privacy in public places crashes with the ever increasing capabilities of law enforcement and companies to register your activities and views.

What is now registered with digital dragnets that can be queried at any time is what would require actual man-hours 50 years ago for just following one person.

That's basically the approach taken in Carpenter v. United States. The Supreme Court said, sure, the police could track people in public with dozens of cars and thousands of man hours, but using CLSI data means it can be done with a few mouse clicks.

You can't apply the "reasonable expectation of privacy" standard when you get into these new electronic forms of surveillance. It's become far too cheap and easy to surveil.

Not that I fully endorse their broaded view of privacy, I see it as much more of a fundamental right. That said, I was impressed that this court(who constantly misunderstands technology) understood this.

I cannot endorse this overbroad definition of "privacy" and in fact I can't see the logic in it at all. It is true that in the past the cops could not automatically hoover up your posts, but is also true that in the past no individual person could reach millions/billions of other individuals instantly with short messages and videos. The increase in scope of police collection of public communications is proportional to the increase in reach of those communications platforms. It is all well-balanced.