A few points I wanted to make, specific to the HN context (and a lot
of this is in the "nerd mode" donation page at
1. This seems like a classic "low effort, high impact" project. It's
super easy to detect aircraft flying in circles, in real-time, and
post it to twitter. But it turns out to be an entry-point into a
"strangely interesting" (according to pg) world of aircraft activity.
The current #1 comment sadly only gets to see general aviation pilots
practicing, but my bots have tweeted military aerial refueling, STOL
practice in the wilderness, float-planes practicing on rivers and
lakes, military drones flying over the desert, planes dropping sterile
fruit flies as a way to reduce the fruit fly population, news
helicopters following a highway pursuit, U.S. Forest Service AH-1Z
Viper attack helicopters fighting fires, helicopters dropping mosquito
pesticide, aerial tankers over Manhattan for the president's combat
air patrol, FBI surveillance planes registered to front companies,
Coast Guard helicopters doing search & rescue, crop dusters,
scientists observing sea life over the ocean, planes doing Gorgon
Stare-style persistent surveillance over Baltimore, sheriff's
helicopters rescuing hikers, power line inspections, pipeline
inspections, military aircraft doing surveillance over protestors,
stealth jet test flights, a Grumman HU-16 Albatross seaplane that
belongs to the USAF over the Mojave desert, a U-2 test flight, and a
B-29. That is not even close to a complete list.
2. All the code is open source. See
3. As far as I know, this comment on HN is the first time anyone
published any significant detail about the FBI's secret aerial
surveillance program: https://news.ycombinator.com/item?id=9508812
I was really confused at first by your use of the phrase.
I also think it is pretty funny if you didn't intend it. I would have thought what you're doing is better described as a "circular advisory" rather than "advisory circular". Cool project :)
I had to Google that. I'll await a correction from a more knowledgeable HNer, but as far as I can tell the US Forest Service does not have AH-1Z Viper attack helicopters.
I don't care enough to dig deeply into it, but it seems that basically there is a very long line of Bell helicopters called "AH-1", going all the way back to the original AH-1 Cobra in 1965. There have been many variants over the decades, and two of these have been been retrofitted into "FireWatch" helicopters for the US Forest Service, after being retired from military service.
The AH-1Z Viper is a modern attack helicopter, a variant of the SuperCobra, itself based on the AH-1 Cobra. It went into service in 2000, whereas the USFS two FireWatch Cobra's were originally built in 1969 and 1983: https://wildfiretoday.com/2010/06/27/firewatch-cobra-helicop...
They're people in small planes practicing.
Also, I live near several military bases. The interesting and loud stuff that I see flying by out my window NEVER shows up on any app. I expect this web site is similarly, deliberately, incomplete.
When it comes to military aircraft, the situation there is kind of interesting. There's no general exception for the military, military aircraft are generally "required" to transmit ADS-B unless they have a specific reason not to (and I believe this requires authorization from somewhere up the chain of command). I put "required" in scare quotes though as many military aircraft are simply not equipped... the DoD has drug its feet on installing ADS-B out and the FAA has basically relented by setting very lax objectives. FAA requested DoD to have ADS-B installed on 21% of aircraft by the first of this year and I believe they met that goal... but it's still less than a quarter.
Over time more and more military aircraft should be appearing in ADS-B data, but I suspect it's going to be some years before it's almost all of them.
C172 and C182 both make fine planes for running surveillance. They're inexpensive (to buy and operate), reliable, inconspicuous, and have enough space and useful load to tack on specialized equipment. I used to own a 182 that was originally owned by the Washington State Police. While in WSP service, it was modified to have an automotive-style muffler for "stealth" surveillance.
According to him, the state much preferred to take cops and turn them into pilots, than to take pilots and turn them into cops. But anyone who wanted to go that route had to pay for their own flight time. (Commercial rating requires 250 hours, and I think they wanted at least a hundred hours "time in type." I don't think they required an ATP rating, but my recollection about that could be incorrect.)
The step up are the B1900s that CBP has which have additional sensor capabilities.
However, if you have a full-sized drone I would love to buy a kit from you.
Perhaps less incomplete than you think (and certainly more complete than the standard tracking websites, which outside of hiding planes also must honor a 5-minute data delay requested by the FAA).
The advisory circular bots the author runs link to https://tar1090.adsbexchange.com/ , which is run from a home-grown network of SDRs. It makes a point of not hiding anything that reports its position with ADS-B -- which all aircraft (over a certain size) must report by law. I've even seen Air Force One and its escorts on this service, something that is always absent from other flight tracking services.
This only applies to FAA-provided data. And I'd not be surprised if it's simply enforced by the FAA only providing 5-minute delayed data.
Tracking sites that use ADS-B are definitely realtime. My kids and I sit outside on the patio sometimes and track the planes coming at our house (we're pretty close to one of the standard ingress routes to PDX).
Can you expand on this for the noobs in the subject?
why the downvotes? this was the actual stated reason when this was requested
For anything not broadcasting ADS-B, you can use multilateration (time difference of arrival) to determine positioning of dumb transponders. Flightaware does this .
I tried briefly googling, but while it's easy to find others talking about the delay , I didn't find a why confirmation
Anyway, it's possible that the reason was no so much ground-to-air missiles but rather ground-to-air weapons. In other words, idiots trying to shooting guns at airplanes or put up balloons in their path.
Is this true? Seems like an unambiguous violation of the first amendment. Someone can't report on raw data that they can receive with an SDR? Has this been litigated?
As another commenter noted, not every aircraft advertises itself using ADS-B, but the majority do - even military. I’m no expert here, but I think the distinction is that military aircraft operating outside of civilian airspace don’t need to. But some do anyway - I’ve seen a U-2 flying at 62k feet over the Southwestern US show up on ADS-B exchange. There’s no need for it to do so, as no civilian aircraft flies at altitudes that high.
Things flying near an airport are excluded ("The centroid of the last 3 minutes worth of positions must be more
than 2.5 km away from all known airports."). I've never seen it tweet about planes doing obvious pattern practice.
This is what the standard training circuit looks like (it's basically a rectangular-ish shape)
This is the type of orbit pattern that is used for search and rescue (SAR) or surveillance (a near-perfect circle, like the ones in the OP) 
 page 127 of this pdf ("Creating an Orbit Pattern") https://static.garmin.com/pumac/190-01007-03_r.pdf
"Computes the total curvature of a sequence of headings."
^double (reduce (fn [^double sum [^double a ^double b]]
(let [d (heading-diff a b)]
(if (spurious-heading-diff d)
(+ sum d))))
(partition 2 1 headings))))
Usually in urban areas there's a more or less formal designated practice area where people are doing these things, intentionally not near the airport, but you could filter out small aircraft in those areas if it was really an issue.
The slightly interesting stuff doesn't show up, the loud jets, but the really interesting stuff does. CIA rendition flights, police spying on protests, Air Force One, rich people flagrantly violating COVID rules ... they all squawk ADS-B.
So, instead of being trackable N123AB, I could fly as DCM965. You could still potentially trace approximately where the aircraft flew (because there aren’t quite enough DCM flights for real anonymity), but it’s more work.
I can enter a new aircraft ID into the box for each flight. That data is then transmitted in bits 9-32 of the ADS-B downlink message (where the N-number is typically transmitted for private aircraft).
Yes, you can change the hex code your aircraft is broadcasting, but the FAA probably won't like that - they will want you to join the PIA program. https://www.faa.gov/nextgen/equipadsb/privacy/
If you don't do all three of those things and keep transmitting your N-number via ADS-B, then you are trackable by N-number. That DCM2790 is using the same flight number for multiple legs and transmitting their N-number is evidence that they aren't maximizing privacy, not that privacy isn't possible.
Don't know if there is an "app", but regarding the interesting stuff, it's the most complete, IMO/E.
Most of the helicopters belong to either TV stations or city/county/state police. There's also medevac, but they don't circle much.
A few weeks ago I was watching an F-35 off the coast of Southern California... so cool to see that stuff. It seems to also pick up weather balloons (or some kind of balloons that are above 60,000ft). Anyway, it's fun to see what's out there.
Are there several? If so what was the key features you were looking for?
I have seen some military aircraft light up while practicing refueling over the pacific, but go dark when leaving or returning to base.
1. Not move there because of flight training schools.
2. Lobby to get the flight training school to practice over unpopulated areas.
I did some flight lessons in rural Manitoba. You got ~45 minutes of flight training for every hour you paid for.
Then I considered restarting them once I moved to Toronto... you get about 20, 25 min of training for every paid hour - the rest is just getting out of restricted space. If you wanted to head to actual "unpopulated area", I think you'd need to book a 3 hour lesson in order to get any actual training. Completely unfeasible.
And this is in Canada, a famously sparsely populated nation. It feels even less feasible for majority of more densely populated countries.
(basically, by definition, if you only allow flight training in the unpopulated boonies, you'd deny it to a very large super-majority of population. One may view that in positive or negative light, of course)
Why is this unfeasible?
Paying 3 hours of very expensive flight training to obtain 30min of actual flight instruction should be unfeasible at plain sight, but fair enough - the next level of detail is "makes it unaffordable, impractical, and is a strong deterrent for vast majority of interested parties".
This is fairly typical — even in urban centers there's typically one or more "training areas" for students to practice maneuvers. e.g. in New York: https://i.imgur.com/Djum5pX.png
 - https://www.bloomberg.com/features/2016-baltimore-secret-sur...
The TARS system is somewhat similar and has been used over the US but relies on a tethered balloon so it's not very mobile, I believe there are two of them, one in the DC area and one in southern NM. For a long time they were sort of infamously inoperational most of the time due to technical issues, and ten the DC one came loose and briefly terrorized Delaware, so I'm not sure how much of the time they're actually active right now. Every time I've gone by the southern NM TARS (not that often but probably several times a year) it's been down.
These overhead persistent surveillance systems are both technically interesting and extremely alarming from a privacy and civil liberties perspective, but it is surprising how little use they've seen in the US. Part of that owes to controversy over their use but honestly a larger part of it seems to just be ongoing technical difficulties in getting them to perform well. Also to be a little snarky I wonder if PSS's weirdly geocities-era website is a factor... when I was doing research papers on these a year or two ago I had a solid ten minutes of disbelief that that was really their actual website. It seems to actually be a very small company.
 sometimes called the imperial boomerang, the colonial boomerang, or Foucault's boomerang
This video is a really cool example: https://www.youtube.com/watch?v=SdfVIdsufI8
The FAA has guidelines on what kind of data you can receive: https://www.faa.gov/nextgen/equipadsb/research/airspace/
I lost interest in it because I just don't speed that much and I don't have a sport bike fast enough for it to matter, but useful to know that ADS-B doesn't cover all aircraft.
So aircraft are perfectly allowed to not transmit ADS-B as long as they stay out of certain types of airspaces and outside of a certain distance of other types of airspaces and etc. So the effective result is pretty much that you need to have ADS-B if you ever want to land at a controlled airport but the details get a little weird.
These rules have also been changing reasonably quickly in federal terms. The current set of ADS-B requirements only took effect the first of this year. Among other things, these rules require that any aircraft equipped with ADS-B out have it turned on at all times... but that's only been the rule as of recently (not sure if this revision or the previous one), so not that long ago it was acceptable to turn it on and off if you were outside of areas where it was required.
Further nit: the rule went into effect on Jan 2 this year, because of the wording of the actual law. It seems likely that the intent was to be on the 1st, but that’s not what was written and enacted.
I believe trackers (like ADS-B exchange) will estimate location using mutlilateration. IE: enough receivers with GPS-sync’d time and knowing where they are can estimate origin with the differences in receipt timing.
With good enough equipment, even one ground station might be able to tell a lot with Doppler shifts. Unsure if that’s don’t in practice though.
This is the most popular mlat server software, used by ADS-B Exchange among others: https://github.com/adsbxchange/mlat-server
You can set up a system for under $120 with a good antenna and a 1090MHz-filtered software defined radio stick. I use the Piaware distribution, which sets up the basic software needed to feed data and to generate your own maps. An added bonus of being a feeder is that you can get free access to commercial ADS-B networks like Flightradar...
Also had an interesting occurrence when I awoke to the sound of a plane dive-bombing my house. We happened to be located in an area designated to be sprayed for some sort of moth. The plane was just about scraping the tops of trees. But I was able to track and see the pattern it flew to spray our area and other areas it had visited that morning.
-- Edward Snowden
With regards to the FBI not caring about your legal activities, I recommend you look into the FBI blackmailing of Martin Luther King Jr. and COINTELPRO more generally. Their historic behavior doesn't exactly warrant trust.
In the case dragnet surveillance, you will constantly become a suspect in investigations based on where you were, what you look like, etc.
If your data doesn't exist in some database, at best you won't be caught up in a dragnet investigation. And at worst, your lack of data saves you from expensive court battles and imprisonment over something you didn't do.
Now when I hear the aircraft above us I instantly check its pattern and lock all the doors.
Last I counted, four of those five are in the same country. The world does not begin and end in America.
You can see the complete list of bots here: https://twitter.com/i/lists/1263724487435890688/members
Cities aren't "destroying themselves". Sure there will be a little change from large office blcoks where companies cram as many people as possible into each square foot, but cities aren't going anywhere.
I'm not saying it's right, I just don't understand the effort and the expense if it's ostensibly justified by the potential for occasions like this, which are now here, and now being effectively ignored by those doing the intelligence gathering.
This creates a very difficult environment for law enforcement. It's not completely clear what the best strategy is for dealing with all this.
Both answers here mischaracterise the nature of protests and the cops.
First, most police actions during protests are legit and don't require some kind of condemnation, certainly not 'jail'. You don't require someone to use force to control a situation then put them in jail if the step one inch over an ambiguous line.
Second, even if there were excessive penalties, it would do absolutely nothing to quell protests. Protestors absolutely do not care about the specifics, they're not even playing that much attention. They're not reading the research on relative levels of violence per arrest etc.. It's a mob. They're angry. Anger is not rational.
Moroever, the most emotionally aggrieved parties do not care about reality. It doesn't matter how professional the police are, they will live their lives on Twitter condemning the 'police state'.
The Police in the US are generally not brutal - they use too much force, but it's not a fascist state. They're not grabbing people randomly and beating them to a pulp as in authoritarian states. Most examples of grievances are relative minor: someone provokes a cop by walking up to them and saying something, the cop pushes the person, they fall down. Not appropriate, but this is not the Stasi. A cop shoots his paintball gun at a reporter - on purpose. Again, not appropriate. But it's a paintball gun, they're used on people - for fun - all the time. If you're going to have 100000 people involved in a physical confrontation, there's going to be some crossing of lines. So yes, make sure the cops who step across the line are punished appropriately - but by and large, it won't make a difference.
Fourth, this idea that there are specific groups of specific trouble makers is generally not the case. It's a mob, emotions sway back and forth. And FYI if this is the obvious case, sometimes police can move in a little bit but otherwise it's not possible. If there is any agitation at all, then this can't really happen because it's extremely dangerous. A group of 100 people could tear a small team of cops limb from limb if they wanted to, not that it would happen to that extent, but remember that mobs are usually much greater in size than the cops.
Fifth - it's not the 'violent' elements. It's everyone. You don't have the right to block a road every day because you want to. Sorry - not in the constitution. You don't get to break the law because you think your cause is legit. Usually, protests are observed and nothing happens if they peter out. But eventually either due to the length of the engagement, or 'night time' protests which turn violent, then things need to be broken up. This is when regular people need to go home. But they won't. So it becomes a problem.
There's no doubt that some police tactics are just too much, and that should change. But for the most part, I don't think it would move the needle on anything. People gather in large numbers, don't want to to home, it's going to get dangerous sometimes, and, they can't continue to stay forever.
If anything the 'real' concern should be around actual policing, i.e. unnecessary police shootings.
> You don't require someone to use force to control a situation
Protests are not something to be "controlled" with force. That's authoritarianism.
> Protestors absolutely do not care about the specifics, they're not even playing that much attention. They're not reading the research on relative levels of violence per arrest etc.. It's a mob
Simple dehumanizing. There have been plenty of protests that have remained peaceful when they're not attacked by police.
> someone provokes a cop by walking up to them and saying something, the cop pushes the person, they fall down
It is illegal to attack someone because you don't like what they've said. This is criminal violence and needs to be prosecuted as such.
> A cop shoots his paintball gun at a reporter - on purpose. Again, not appropriate. But it's a paintball gun, they're used on people - for fun - all the time
It is illegal to shoot random people with paintballs. This is criminal violence and needs to be prosecuted as such.
> You don't have the right to block a road every day because you want to
Roads are public ways. People do have the right to use public ways to peaceably assemble.
> If anything the 'real' concern should be around actual policing, i.e. unnecessary police shootings.
That's exactly what these protests are about. Instead of accepting the message and submitting to accountability under the rule of law, police departments are escalating the protests so they can paint the protestors in a bad light, just as you are doing.
Do they have the right to block the road while doing so? For hours?
More big-picture, I don't buy either your narrative or jariel's. I don't think the protesters are a mob. I also don't think that the violence is mostly because of the police.
I see it like this: There are two groups, the protesters and the troublemakers. There is some overlap, but they are largely two distinct groups. A protest happens. It's usually in the daytime. The population is mostly protesters. Things are mostly peaceful. There is probably a police presence, watching the protest, but they usually don't do much.
Time passes. Around sunset, many of the protesters go home. More troublemakers show up. It looks like the same protest, but the nature of the population has changed. There starts to be some acts of vandalism, maybe some assaults, maybe some throwing things at the police. Eventually the police say that it's enough. They either order the crowd to disperse, or try to arrest someone. The crowd, being by this time mostly troublemakers, won't disperse peacefully and won't accept having one of their members arrested without going the rounds with the cops. You now get videos with the starting point very carefully chosen to make the cops look like the instigators.
Now, I am not saying that the cops never start the violence. I am not saying that only troublemakers are around after sundown. I am not saying that all videos of police violence are refusing to show the antecedent/buildup. I am not saying that everyone the cops get physical with had it coming.
I am saying that the majority of the action follows the scenario I described.
Phrasing it as "blocking the road" is dragging in a bunch of assumptions. Another way of looking at it is that the protestors are using the road to the exclusion of others, in the same way that a parade or even rush hour traffic does. This is a judgment call, but given that protests aren't terribly common, I think the large group of people doing work to air their grievances deserves the benefit of the doubt. Remember, the entire point of a protest is to express outrage in a way that may be uncomfortable for everyone else.
> Eventually the police say that it's enough. They either order the crowd to disperse, or try to arrest someone. The crowd, being by this time mostly troublemakers, won't disperse peacefully and won't accept having one of their members arrested without going the rounds with the cops
This is the crux of the problem - the police asserting that they have the right to say "that's enough", declare a protest over, and then commit violence against anyone in the area. The dynamic is accelerated since the protest is explicitly against the police.
The police need to either stick to arresting specific people committing crimes, or withdraw and accept that their authority has become overwhelmed in an area. Escalating the lawlessness by committing violence against the entire group is unacceptable in a society based around individual freedom.
And I argue that it should in fact be that way, at least in some circumstances. If you have a large group of people, some of whom are committing, say, vandalism, and the group's boldness is growing as they see that they can get away with such acts, and the group is making kind of a compact body, so that it's difficult for officers to reach and arrest any individual who has committed a crime, then... what? Just let it go on, because it's "just vandalism" (so far)? Then what do you do when it isn't just vandalism (if in fact it continues to escalate)? Or do you just trust that it won't continue to escalate? "Just trust people who are already breaking laws" doesn't seem like a reasonable police approach. Or do you just let it escalate however far it's going to, because violence by the police is unacceptable in all cases?
> I think the large group of people doing work to air their grievances deserves the benefit of the doubt.
I do, too... but not forever. That is, they want to block a road for a protest? Sure. It's inconvenient, but they have the right. They want to block it every day for two months? That's a bit of a different question.
When a large group has collectively decided to abandon some laws, the rule of law has already broken down. Citizens rightly outnumber police, and looking for a top-down response is fallacious. The real question to be asking is why have so many citizens become so disenfranchised as to start rejecting laws? For protests, answering this is quite straightforward - the entire point of a protest is to tell you.
At what point are police justified in attacking a rowdy group? At the very least it needs to be equitable. If the group is committing property crimes such as vandalism and graffiti, responding with physical violence is itself a significant escalation.
Furthermore, I don't think it's fair to assert that the group will continue to escalate - just because they have abandoned respect for some laws does not mean the group has abandoned all moral code.
As I started off saying, the real solution to policing low level crimes is to deploy small units of officers distributed throughout the group. If those officers are attacked, only then do they have the right to defend themselves with force. What the police have been doing in the name of control has mostly been a state sanctioned counter protest, complete with battle lines.
It sounds like your idea of a protest is necessarily aggravating. That may be non-violent, but it isn't peaceful.
> unacceptable in a society based around individual freedom
The mob aren't acting as individuals - which is the point, and any actual individuals are no longer free to use the road, which has been taken to the exclusion of others - your freedom has to end where in limits mine.
Also, a large component of the threat posed by the mob is the anonymity it grants individuals to commit crimes; No society based around individual freedom should allow that kind of freedom.
"No justice, no peace". Yes, protests obviously aren't peaceful. They're also generally responses to conditions that are not peaceful. If this is supposed to be a condemnation, then I'm happy that online petitions suffice for you.
> individuals are no longer free to use the road
Just like parades or rush hour traffic, as I said.
I think it's pretty easy for law enforcement to do the right thing: Don't show up.
When cops don't show up there is little to no violence against people or property.
When cops show up to protests more often than not they initiate violence against people and retaliate for violence against property (or their reputation) with violence against people. This is some fuuuuuuked up behavior and why the protests continue.
Responding to protests against police brutality by violently brutalizing protestors is like a really sad joke.
A random "individual"? No.
The very individual breaking those windows, or stealing those shoes? I'm not sure as many would agree.
A car, or property - possible your property; I think many would demand violent injury as just retribution.
The bigger issue are planes that are't showing up anywhere. I think it would be interesting to pair some audio and computer vision resources with existing ADSB network to train what planes sound like and possibly even which altitude/direction they are traveling based on sound energy alone.
Camera would be nice, also passive radar given that most of these ADSB tools are using existing software defined radios.