It's a Sunday, so there's not too much activity. However there's currently an FBI Cessna circling west of Washington D.C.  There's also a plane gridding east of LA.  It's registered to Dynamic Aviation Group out of Virginia, a company that provides aerial intelligence, surveillance, and reconnaissance (ISR), among other things. 
ADS-B reduces controller workload as they don't have to manually tag individual aircraft, especially in a high traffic area. ADS-B also works without secondary radar interrogation.
When there is a high speed chase near an airport, sometimes the tower controller will request the helicopter remain under a certain altitude or clear of a specific area.
Additionally, websites like FlightAware.com have limited direct ADS-B coverage and also display the FAA 5-minute delayed feed. I've never heard of a "criminal" in the US using an ADS-B receiver to evade police helicopters in real time.
Mode-C and Mode-S responses are sent when interrogated by secondary radar. ADS-B transponders with "Extended Squitter" transmit regularly while active, so no need to transmit your own interrogation pulses.
Its possible to monitor Secondary Radar pulses, and Mode C returns. It would require multiple geographically separated receivers to triangulate. I don't think FlightAware supports Mode C, only Mode S(MLAT) and ADS-B.
If you transmitted your own "secondary radar" pulses, the FAA and/or the FCC would probably launch a criminal investigation, with the FBI involved. Making your own "secondary radar" would be pointless and high risk.
Exactly. Police helicopters fly low enough that unless they are on the final approach or departure path, its not a big deal.
Its a common misconception that because news helicopters following the chase are denied clearance to fly near an airport, the same would apply to the police helicopters.
There's a lot of info online about Dynamic Aviation doing Sterile Insect Technique flights over southern California, and their contracts to do so.
There are other spooky defense contractors doing what may be imagery collection flights, though. Like KEYW: https://twitter.com/lemonodor/status/647109884488454144
SAN BERNARDINO COUNTY SHERIFFS DEPARTMENT - SAN BERNARDINO, CA
No location coordinates provided though. I wonder if this is anything related to an ongoing investigation, or just a coincidence?
Also, for the tag "interesting", I see only one (UK something).. Is it because I'm in Europe?
here's the summary,
> In 2004, when casualties in Iraq were rising due to roadside bombs, Ross McNutt and his team came up with an idea. With a small plane and a 44 mega-pixel camera, they figured out how to watch an entire city all at once, all day long. Whenever a bomb detonated, they could zoom onto that spot and then, because this eye in the sky had been there all along, they could scroll back in time and see - literally see - who planted it. After the war, Ross McNutt retired from the airforce, and brought this technology back home with him. Manoush Zomorodi and Alex Goldmark from the podcast “Note to Self” give us the low-down on Ross’s unique brand of persistent surveillance, from Juarez, Mexico to Dayton, Ohio. Then, once we realize what we can do, we wonder whether we should.
Ross McNutt is simply selling a product, and cameras are easier to sell than radar sensors.
- The article points out that the planes are typically only seen M-F, which suggests that what they are doing is usually not time-sensitive.
- They mention the planes have a very high quality camera on board.
- From the flight patterns, you can see they repeatedly circle the same location, but not apparently for hours and hours at time.
When Apple first released their Maps product, it was revealed that they also flew planes at low altitude to capture super high quality pictures of cities at different angles. They would then process the data later and create 3D models. 
Satellites are too expensive to use for this sort of thing, are affected by cloud cover and non-optimal angles, and won't be higher quality than what you can capture from a plane.
So my guess is they are doing exactly what Apple was doing: capturing high quality images of various points of interest and then creating 3D models in case they need to use them later.
Another thing they are probably looking for (from the mention of the FLIR camera) is people growing drugs in their basement or perhaps where people congregate in a building.
They probably find this useful for among other things, having very up to date photography of a particular area, and also in case they need it for some operation like a raid.
That is changing.
I'm not sure balloons could give adequate control, but drones are a great idea and I look forward to the day when they are so cheap that the same amount of tax money can pay for drastically increased surveillance from the sky.
Drones probably have legal issues, big ones (range, payload) are also quite expensive to build and operate and require more specialized skills (unless there are tons of ex-military drone operators to be hired cheaply?). Would also probably attract more attention.
Blimps have been proposed and tested for all kinds of surveillance tasks, but you'd get the main benefit again if they were autonomous. Seems to be in development, but not there yet.
There's a pretty complete description of what they did in the Form 337 history: http://mike.laiosa.org/N6594E/Airworthiness.pdf - see in particular pages 27 and 55.
Police surveillance, makes sense, relatively inexpensive to operate, but good loading for whatever gear they're carrying.
Unfortunately most of my family gets horribly air sick, so mine is for sale - I'm looking for something cheaper to operate and cheaper to buy.
That said, this planes survalence package was probably a guy in the right seat with a 35mm camera. If a camera was mounted on the belly or a window for one installed, that would appear in the airworthiness history. And besides, the police operated this plane in the 80s and 90s, when taking a zillion pictures and sorting through them later wasn't economic.
But then I got into photography. And in that case, police were trying to trample on the rights of photographers. But the main idea is that photographers are allowed to photograph pretty much anywhere in public. And I agree with this. You can't make laws forbidding photographing a particular building, for example.
That got me thinking, if we can't forbid citizens from photographing in public, why should we forbid our government? In fact, when crimes happen, most of the time these days, video surveillance is a huge help.
If that data were made publicly accessible, would it be a problem that it was being recorded? What are the drawbacks of public surveillance?
I don't understand this comparison. The very fact that the surveillance is being done by the government changes the meaning of the action. Citizens don't have the power to do anything with the information they might gather through surveillance. Citizens don't have the ability to force all other citizens to pay them more money for funding surveillance programs of ever-increasing scope. Citizens have jobs which exist to serve a real need that exists in the economy, and so realistically wouldn't be doing anything of the same magnitude unless there was popular demand for it.
In fact, your argument is somewhat ironic, as it is the same logic used by the police to prevent photographers from photographing in public, as descibed by the OP.
If we can't forbid citizens from promoting a religion, why should we forbid our government?
If we can't forbid businesses from cutting unprofitable departments, why should we forbid our government?
If we can allow businesses to be run by the same people indefinitely, why should we forbid our government?
It has taken society centuries to come to the notions of privacy and public rights against the state that we have today. If the aggregation, retention and analysis enabled by technology changes things, as I think they do, and I think many of us here think they do, then we as a society have our work cut out for us to update our notions of privacy.
The people in Surrey had to make a decision as to whether they prefer living in a crime-ridden shithole, or if they prefer 24-hour surveillance. They chose the surveillance.
The reality is that most people are happy with some level of surveillance if it is done to reduce crime. There seems to be an automatic presumption by some people on HN (which appears to be a majority of HN users, based on upvotes/downvotes) that the US government is like some kind of Stasi police state. The reality is that there is always pushback when the government oversteps its bounds. Some examples: investigations into torture by the CIA, the FBI now getting warrants for Stingray operations, the Snowden fallout, etc. I guess it's good that there is a strong libertarian contingent in the USA, which helps keep your government in check.
We should forbid our government because they have power, and it ought to be limited.
Edit: Also, check out Los Angeles (if that's not where you are from). They are swarming LA! I'd be weirded out if I was in LA and NOT near activity.
Normally, one would think that a communication that has been intercepted and stored in a government database as “collected.” But the government’s definition of what it means to “collect” intelligence information is quite different than its plain meaning.
Under Department of Defense regulations, information is considered to be “collected” only after it has been “received for use by an employee of a DoD intelligence component,” and “data acquired by electronic means is ‘collected’ only when it has been processed into intelligible form.”
In other words, the NSA can intercept and store communications in its data base, then have an algorithm search them for key words and analyze the meta data without ever considering the communications “collected.”
Here's a fun clip of the Iraqis using a 208 to launch a hellfire. https://youtu.be/eSKsrILHxNM?t=57s
2. FBI is both a law enforcement and intelligence organization.
The last aerial surveillance case I can recall is California v. Ciraolo, which was about surveillance with the naked eye. I hope that these flights wouldn't survive a legal challenge, but I also believe that the FBI would be likely to launder anything gathered via parallel construction -- engineering a "normal" traffic stop, etc., based on gathered information.
As with the use of Stingrays, secrecy is used to thwart justice. I don't know how to stop it.
What objection do you have with the FBI tracking criminal suspects from the air?
Do you also object to the FBI staking out suspects from their cars?
(I'm not referring to Stingrays here, just surveillance from the air with cameras/eyeballs).
"cameras/eyeballs"... you understand that those are two different things, right?
Large area digital data collection is not the same as observing an area with the naked eye.
Deployed networks of automated license plate readers are not the same as "the FBI staking out suspects from their cars".
I realise that, but you said "I hope that these flights wouldn't survive a legal challenge" so I inferred that you thought the judgement was incorrect.
>"cameras/eyeballs"... you understand that those are two different things, right?
I'm not sure if you're trolling here. The slash meant "or" in this case, which should be been patently obvious.
>Large area digital data collection is not the same as observing an area with the naked eye.
Of course, and it's not illegal AFAIK.
>Deployed networks of automated license plate readers are not the same as "the FBI staking out suspects from their cars".
The article doesn't mention "automated license plate readers".
Sounds like a crock if I ever heard one.
Not everything is a conspiracy.
They are hiding it by using front companies, etc. So I think it qualifies as a conspiracy.
I think the similar argument here would be that a near constant observation of someone, even while in public, would amount to the same sort of search, even though one has a very low expectation of privacy while in public.
Swap "GPS monitoring" for infrared, EMF, video, audio tracking, whatever those planes are doing, and I think we are at the same level of "impinge(ment) on expectations of privacy."
Is it your opinion that Alito and Sotomayor are barking up the wrong tree? Is this sort of extensive (i.e. multi-modal (visual, EMF, etc.)), and evidently prolonged, monitoring not an impingement on typical expectation of privacy? Sure, this isn't a trespass, but if a private person was doing this to you, wouldn't you want to call the cops? (Oh, wait...)
In my opinion, the whole "expectation of privacy" thing is reading words into the 4th amendment that aren't there. If you look at the phrasing of the text, which focuses on "searches" and "seizures" of "persons, houses, papers, and effects" it's clear that the 4th amendment prohibits the government from doing what would be a common law trespass (to the person, to real property, or to chattels). It's based on property rights, not privacy.
That's because it would be stalking.
If you are following someone in the matter the police would they won't know they are being followed, which is part of what private investigators do.
Just don't harass them. If they catch you and tell you to stop and you don't - then you are veering into harassment territory.
You can't investigate a criminal/terrorist and simultaneously tell the public exactly what you're doing, step by step. It's not practical.
There are tradeoffs we all have to make. Idealism isn't compatible with the kind of work the fbi does.
Wouldn't it be dangerous to fly a plane "in-secret"?
Of course, all of this supposes that it's important enough to be secret. It actually helps secrecy to fly some of these missions openly, meaning it's harder to find the ones that are clandestine.
Edit: and mosque home, workplace and mosque.
The reason I wrote the comment initially is because it seemed off to me—like showing up to a business meeting at a law firm in a pink and yellow plaid suit.
I was wrong.