Flightradar24 – how it works | Hacker News Reader

Flightradar24 – how it works

habr.com

874 pointscrunchiebones155 comments

“Every civilian airliner is equipped with a special device — the so-caller ADS-B (Automatic Dependent Surveillance-Broadcast) transponder”

Not true actually: in the US, ADS-B isn’t required until January 1, 2020 [1].

Also, FR24 uses radar data in the US (probably because not all aircraft has ADS-B) [2].

There are also sites, such as ADS-B Exchange [3] that provide unfiltered flight data...very helpful for tracking military flights and such.

[1] https://www.faa.gov/nextgen/programs/adsb/faq/#g2

[2] https://www.flightradar24.com/how-it-works

[3] https://www.adsbexchange.com

Even after 2020 ADS-B out won't be required in much of the airspace in the US. Only within 30 nautical miles of a class B airport, within the lateral limits of a class C airport, within class D airspace, and above 10k feet (but not below 2500 AGL I think). Even then, its only required for aircraft originally equipped with an alternator and electrical system (except in class B).

Basically, it's optional in most uncontrolled airspace and for older aircraft.

In practice, anything that can be described as an "airliner" is a large commercial aircraft and flies above 10k regularly. Probably required to have ADS-B.

Oh whoops, I misread as "airplane"

AU: Another good example where it'd pay off to use the 'FQDN', transport category aircraft.

To be fair, that's going to include the vast majority of aircraft. Most people will be above 2500AGL if they're not flying for very short distances. That said, there's always people that just like to fly in an unsafe manner.

Sorry, I may have worded that confusingly. The important number is 10,000 MSL. If you don't go above that you don't need ADS-B (as long as you stay out of the other airspace mentioned). They make an exception for people flying around high terrain, so if you are above 10,000 MSL but below 2,500 AGL then you are also exempt.

What is "uncontrolled airspace"?

https://en.wikipedia.org/wiki/Uncontrolled_airspace

Flightaware hardware will perform multilateration (using time distance of arrival) for transponders not announcing location via ADS-B.

https://flightaware.com/adsb/mlat/

If you use macOS you might enjoy my app Max Planes [1]. It displays all the ADS-B data, tracks planes on a MapKit view and allows you to save and replay logs.

Also I have an open source Mac app [2] to act a network server for the USB device. It contains a copy of dump1090 with everything statically linked so you don't need to build anything yourself. Just plug in the dongle and launch the app. It is codesigned, sandboxed and notorized.

You can also use the prebuilt dump1090 binary included inside the App.

[1] https://mtlabs.com.au/planes/

[2] https://github.com/mxswd/dump1090-mac-app

Very cool - I will try that one, just need an SDR.

Very nice ADS-B viewer for macOS! Quickly got it connected to dump1090-mutability once I set the bind host to 0.0.0.0 instead of localhost. I wish planes were differently colored based on certain characteristics, much like OpenADSB on iOS (the best ADS-B app IMHO)

EDIT: Also, do you support MLAT?

I am the author of OpenADSB, thanks for the kind words. Please don't hesitate to reach out if you have any suggestions or feature requests.

For those that don't know, OpenADSB is an iPhone/iPad app that connects to any Virtual Radar Server and dump1090 server. ADSBexchange runs on VRS and dump1090 is the de facto Raspberry Pi ADS-B decoder. OpenADSB is not affiliated with but uses ADSBexchange as the default datasource.

https://itunes.apple.com/us/app/openadsb/id1178703539 http://openadsbapp.com/

Worth nothing that if you're in a area with poor coverage, Flightradar24 might be willing to send you a free receiver https://www.flightradar24.com/add-coverage

Page above also have a similar guide to this submission.

I mainly started contributing with data only because you'll be able to get a free business account with Flightradar24 if you contribute, which gives you longer history to view, and bunch of more map layers to use.

Article did note, at length.

In case you are interested in this kind of things there's also the same for ships:

https://www.marinetraffic.com

https://www.vesselfinder.com

https://www.openseamap.org

Aishub is also applicable, they have a great model.

Not a big fan of "data monopolies" like Flightradar24. It's as if OpenStreetMaps was a private company that capitalizes on being first into the space and having a community of contributors willing to supply data to a private company for free. I hope an open data project such as https://www.adsbexchange.com/ wins in the long-term.

I thought it would be cool to have some kind of gateway service that collects the data and then sends if off to adsbexchange, flightradar and others but apparently it's not so easy.

Someone else already asked this question before:

https://www.reddit.com/r/ADSB/comments/ar3qrw/feed_to_a_sing...

Do you mean collect data from multiple receivers and send it off to various services from one computer? That messes with MLAT [0] calculations and shouldn't be done.

If you want to send data to multiple services from one receiver all you need is to install the feeder for each service. Most uses dump1090 [1], but Flightradar24 uses their own. Dump1090 sends data in different formats to various local ports by default, and ADS-b Exchange uses netcat to send it to their server. You can use the ADS-B Receiver Project [2] to install everything needed.

[0] https://en.wikipedia.org/wiki/Multilateration

[1] https://github.com/flightaware/dump1090

[2] https://github.com/jprochazka/adsb-receiver

Thanks for the explanation. I was referring to the second use case and I didn’t know it’s so easy. So I guess it’s not that big of a problem.

Do you have more detail on how collection messes with MLAT calculations? It seems like for triangulation purposes, each device should produce some precise timestamp that is not affected by store-and-forward transmission.

Unfortunately, there is no good solution for this. Either you rely on the time settings of the sender or on the time needed to transmit the data and on the time the data gets transmitted.

A radio receiver with a GPS time base doesnt seem that tricky.

If we assume the sender is not malicious, a properly configured NTP client ("the time settings of the sender") would probably suffice. If the sender is malicious, unless you somehow make the "signal + timestamp" from the receiver non-modifiable from the receiver to the service, you've lost anyway.

Because MLAT relies on multiple devices, it should be straightforward to identify and blacklist a sender tampering with timing data.

I don't think the programs are made to handle that use case. At present you register your receiver's location with the server once and send packets as they arrive, that server doesn't know that your packets are from multiple receivers at multiple locations.

https://discussions.flightaware.com/t/aggregation-of-dump109...

https://github.com/mutability/mlat-client

If you aren't trying to send MLAT data to more than one server, it isn't an issue. You can do MLAT to, say, adsbexchange, and non-MLAT to flightradar24.

You'd still need to send the mlat messages from each receiver though, you can't aggregate them from one computer since there's no position included in the sent messages. And I don't know why it would be a problem to feed from each receiver, they need connectivity any way.

Is there an open version for ship data as well?

https://www.openseamap.org

Great! They don't seem to have historic ship positions though.. hm.

It seems like none of the AIS providers store historic ship positions, you probably have to do it yourself if you want that information

It seems possible to make AIS receiver using RTL-SDR + RPI. I am about to make it, there's a couple of guides online.

AIS isn’t long range though. You’d need an incredible amount of base stations for any sort of decent coverage of frequented areas.

50k radius if not more off a 10 sailboat mast. In context of sailing boat that you only meed couple of kilometers.

BTW new Iridiums are capturing AIS and ADS-B from satelite.

Last I checked there AISHub was the biggest reusable source of AIS data. Coverage map here: http://www.aishub.net/coverage. They are used by various sites like https://www.vesselfinder.com/

MarineTraffic has a more comprehensive monitoring network but they keep the data to themselves. Details at https://www.marinetraffic.com/en/p/expand-coverage

As noted by another comment, AIS signals are being broadcast line-of-sight from the ground so you need more receivers than you do to track airplanes. OTOH you only need the receivers on the coastlines and on major inland waterways, not over the whole earth's surface. (If you want to track a ship mid-ocean, you'll need a satellite. Those exist but cost $$.)

Flightradar24 is probably one of the better flight trackers out there. It is well supported and has a polished easy to use interface.

They are only a “data monopoly” because they are good at what they do.

Not sure if you mean easy to use interface for contributors or for users. I can only judge the second, and the website is "meh"... it's kind of slow and the UI and design is underwhelming.

In any case, being good at what they do definitely helps, but network effects is also a factor. They have the best data coverage, therefore new contributors will mainly chose them over a hypothetical competitor with a slightly better support and user interface.

This discourages new competitors to even try entering the market, which has the usual downsides of a monopoly market such as less innovation.

There's also https://opensky-network.org/

Their API is actually a bit more open than adsbexchange's

How is the data coverage compared to flightradar?

Last time I looked closely it was similar in North America and Europe. Asia, Africa, and over the oceans had some pretty big gaps.

There's also no delay on the data, although I think Flightradar and Flightaware dropped the 5 minute delay they used to have. Flightradar censors a lot of corporate jets and military/law enforcement aircraft but I don't think Opensky does. In fact one of either Opensky or adsbexchange even has a special flag in their REST API for "interesting" aircraft

The delay was a rule from the FAA for radar data provided by them, ADS-B plots have always been real-time. I am guessing (from the lack of orange icons anymore) that the ADS-B coverage is good enough now that FR24 is not using FAA feeds any more.

> I think Flightradar and Flightaware dropped the 5 minute delay they used to have

I was using Flightradar yesterday and visually tracking planes, seems like about a 10 second delay.

Using their UI, I can't seem to find the "interesting aircraft" tag. Here's what I see:

  * No data
  * No ADS-B Emitter Category Information
  * Light (<15500 lbs)
  * Small (15500 to 75000 lbs)
  * Large (75500 to 300000 lbs)
  * High Vortex Large (aircraft such as B-757
  * Heavy (> 300000 lbs)
  * High Performance (> 5g acceleration and 400 kts)
  * Rotorcraft
  * Glider / sailplane
  * Lighter-than-air
  * Parachutist / Skydiver
  * Ultralight / hang-glider / paraglider
  * Reserved
  * Unmanned Aerial Vehicle
  * Space / Trans-atmospheric vehicle
  * Surface Vehicle – Emergency Vehicle
  * Surface Vehicle – Service Vehicle
  * Point Obstacle (includes tethered balloons)
  * Cluster Obstacle
  * Line Obstacle

Yeah that was actually with adsbexchange (https://www.adsbexchange.com/currently-airborne-interesting-...).

That's really interesting, there are two Project Balloons high over the Brasilian Amazon.

> Flightradar censors a lot of corporate jets and military/law enforcement aircraft

Yes, this is disappointing. In the past I had seen military planes on there. I even saw fighters practising dogfighting over the North Sea. But more recently I've seen interesting aircraft fly over, such as large four-engine planes at altitude outside of normal commercial flight paths, but they just don't appear on flightradar. It's stupid because I can see the damn thing. I need to figure out an alternative to flightradar, it seems.

ADS-B Exchange [0] has a tag for military aircraft, right now it's showing a whole bunch of military aircraft (German, Belgium, Norway, Netherlands, UK, US) over central Europe.

[0] https://global.adsbexchange.com/VirtualRadar/desktop.html

Cool, that looks much better, thanks.

Note that even the Swedish spy plane is using Ads-b while flying along the baltic International border zone taunting Russia but the migs answering the taunt is not. Also flying dangerously close to the spy plane (10 m reported once). However the US spy planes are also mostly flying with the transponder on there.

Some activists were using this kind of service to track dictator's flights to track stolen money [1]. If said dictator's can block their aircraft, the misappropriated funds would be easier to sneak out of the country.

[1] https://news.ycombinator.com/item?id=12700445

Note that the OpenStreetMap Foundation is a private company (it's not a for profit company, but it's organized as a company under UK law), probably is the first (at least large scale general purpose) crowd sourced map, and supplies data for free to anyone that meets the terms of the ODBL.

Completely agree. FR24, along with FlightAware, Radarbox24 and Plane Finder has built a business of monetizing free, crowdsourced data. For FR24 there's been multiple requests by the community to for an API, some willing to pay, but they've refused every time. I don't understand why people are eager to feed into those closed network.

ADSB Exchange on the other hand is built with an open premise, runs off donations, and encourages third-party app and value add to build off their API.

Well, we can do both. FlightAware has nice tutorials and client software for setting up an ADSB feeder on a Raspberry Pi, but I feed to ADSB Exchange as well with minimal extra effort.

There's probably not much stopping FR24 from feeding off of ADSB Exchange. This happens in the weather world, where data from community-managed CWOP weather stations ends up in the hands of commercial weather data services, who normalize the feeds and incorporate them into their forecasting products.

Isn't there some kind of "free to use, but not to commercialize" license the CWOP people could be releasing their data under?

That gets into the very tricky idea of "What is commercialization?" If you use a Creative Commons works that's BY-NC on your blog, but your blog runs ads, is it now commercial? What if it's funded by Patreon? That's why Wikipedia doesn't allow NC and the premise behind the Free Culture licenses.

They also started out with a fairly expensive premium app, and then jettisoned it in favor of a subscription-based service, leaving everyone who bought the app high and dry.

You are always welcome to feed more than one service. Even when you get a free receiver from the company, nothing stops you from repurposing the data and feeding elsewhere.

Also, Flightradar hides some of the data from public view [1].

[1] https://www.flightradar24.com/business/aircraft-unblocking

"Data monopoly" implies FR24 have exclusive use and control over the ADS-B feeders. This simply isn't the case. There's nothing stopping you feeding your data to other sites/apps. Also (as is the case with flight aware), all users providing ADS-B data get free subscriptions to the paid for parts of FR24s service.

Building an app, maintaining a website (that has something like 2 million daily users iirc) and building out backend infra to support the huge amount of incoming data and turn it into something greater than the sum of its parts costs money. What many people don't realise is the data you see on FR24 is not simply derived from ADS-B broadcasts. Data like fight numbers comes from other licensed sources; MLAT triangulation is done at FR24's end; telemetry data for areas without community ADS-B coverage comes from partnerships with radar operators, airports (and soon satellite, when Aireon is active) etc.

If you're curious to know what raw info is included in a typical broadcast, this is a good link: https://www.adsbexchange.com/datafields/

> There's nothing stopping you feeding your data to other sites/apps

Except the TOS, if you're using one of their receiver kits.

Don't use one of their kits...

In Germany receiving ADS-B used to be illegal (I don't think it has changed, but I did not verify.)

In Finland receiving as such is not illegal, but forwarding the information is.

In both cases the reasoning is that this information is not directed to the public. Whether anybody has ever been prosecuted I have no idea.

That seems very odd. Somewhat similar to putting up a billboard then saying it's illegal for people to read it, as the billboard wasn't intended for them.

Someone putting a car in the middle of nowhere doesn’t leave it there for anyone ti pickup.

But it is pretty OK to look at the license plate...

Is it also OK for that license plate to be shown to the world together with its location and time?

But we are not "picking up" the car. The car is still there for its owner. We only recorded the presence of the car (radio transmission) for our own purposes and it is unmolested.

Nah - you're specifically using technology that allows you to set any frequency you want, but instead, you're picking the frequency that is illegal for you to listen to and then you're recording it.

Moreover - when you finally get caught, on which scale do you have to be doing it to get caught in the first place? Remember - laws don't exist outside reality.

And let's be honest - the recording of the presence of a car is also quite illegal in certain jurisdictions. e.g. Germany.

It looks like it was legalized a while ago: https://lawfactory.de/PDF/Funkamateur_2010_03.pdf (in German)

Thanks for this link.

> It looks like it was legalized a while ago

Interesting enough the law has not been changed. The article tells how officials forbade a trader to sell ADS-B receivers to the public. The trader went into court and won. The reasoning of the court was that the law forbids only listening. But because the ADS-B signal is not made audible, but visualized on a PC screen, the law is not applicable.

This was only a medium court. Another one or a higher one might decide differently. Probably you should start lobbying that lawmakers will not "adapt the law to the digital age" when revising it the next time.

In Finnish law the construction is different. All radio communication is considered confidential unless otherwise stated, like e.g. for radio and TV programs. Receiving such confidential information is not criminalized, but sharing it further is.

It may still be the case in the UK that it's illegal to receive ('intercept') radio communications not intended for your consumption, even if they're broadcast in the clear. It's not an unusual class of law, does make some sort of sense (even if enforcement is very hard!) and it seems like receiving ADS-B would be covered by that.

Rtl-sdrs are great, probably one of the best accidental discoveries I've seen. So many things being sent out from 0-1.5GHz that you can sniff. One that I see often are the unencrypted pagers broadcasting patient details, hotel security information etc. Then you've also got amateur radio, air traffic control, GSM, key fobs, weather stations, satellites, all within the reach of anyone with $15 to spare.

I want[ed] to get one but the options are overwhelming. I dislike buying not-the-best product. I also dislike eBay, which seems to be one of the main methods of purchasing a setup (have been burned too many times by sellers).

Buy the kit from rtl-sdr.com -- no need to use ebay and they are the best option for a beginner

Thanks! Bought one for myself and a second for my Ham radio enthusiast father.

Consider also an FM band-stop filter and an LNA, apparently makes things so much better. Even with the antenna removed I can still hear FM broadcast, ruins the whole band. I've just ordered those two, want to test it with NOAA reception.

Allow me to point you to SDRplay who have a line of USB receivers that are far more capable (more sensitive, less overwhelmed by strong signals, wider capture bandwidth, wider frequency range) than any of the RTL dongles, which only cover shortwave (<30MHz) with basically a hack. I like SDR Console as the software for this.

https://www.sdrplay.com/

I use https://github.com/bemasher/rtlamr for tracking my electric and gas usage on a minute-by-minute basis.

There's also a community-based ADS-B site: https://www.adsbexchange.com/

And a subreddit about ADSB: https://www.reddit.com/r/ADSB/

I use http://360radar.co.uk, which is a small site run by (I think) just one guy, but it has the best coverage hands down for the UK. It's used extensively by military aircraft enthusiasts in the UK as it'll usually show some stuff that isn't on adsbexchange, and provides some nice features such as aerodrome and weather layers in the UI.

Extra notes: 1) You can share the same data to multiple sites from dump1090, not just FR24. 2) I see no difference between the $27 and $9 version of SDR. I can recommend this one: https://www.dx.com/p/rtl2832u-r820t-mini-dvb-t-dab-fm-usb-di... Running on two different computers and switching between them give the same number of planes spotted. The $9 actually seems a hint better. 3) I can recommend saving your own data to a sqlite3-database (https://github.com/yanofsky/dump1090-stream-parser). Easy to work with and under <50MB/month. Fun to write more advanced sql's to count number of time helicopter take-off, the same plane over your house etc. that FR24 can't give you.

Perfect timing. I'm just in the process of building my own shortwave listening station in Lahore, Pakistan — which is definitely a low coverage area on both services. I was using a RTL-SDR + Pi and a homebrew antenna to cover the 2m band, so I guess I could run this in parallel. I was looking at volunteer run air quality monitoring services just this morning!

Just filled their forms. Slightly concerned about running a blackbox on my network so I'll have to do some isolation, but this'll be a fun contribution.

Here's someone spoofing a fake aircraft this way: https://www.ainonline.com/aviation-news/air-transport/2012-0...

That presentation is something that interested me in ADS-B in the first place. Not because I want to spoof airplanes, but because of novelty of this project.

Bait and switch app. They convinced me to fork out for the fully paid version, then switched to a subscription model that froze current features for those who had supported their work, adding a nag and an implied threat of end of life. Stay away.

There's also https://planefinder.net

Thank you!

Lee (CTO @ Plane Finder)

Hey Lee,

Just took a look at your website, I was looking for some kind of historical flight data provider.

Clicked on the "Historical Flight Data" link and it just links to a couple popular flights which in turn link to pages with a few pieces of flight data visualized/available.

Clicked on the "Commercial Services" link and it details a few commercial services including "Historical Flight Data" which says

> Looking for historical flight data? Plane Finder historical flight data is available in 5 minute or 1 minute intervals dating back to 2011 and is delivered as flat files in CSV format.

"Historical Flight Data" isn't clickable, and I don't want to fill out a form ("Contact Us"), so I click on "View Products" which just links me to your downloadable apps.

Apologies if there's something I'm missing.

I'm trying to get a look at API docs and pricing, and sign up and get started without having to "contact your team."

Is there a simple solution to get a basic offline map (OSM maybe) and use a pi without internet as a radar display at my local non-towered airport?

Yes. A cheap DVB-T dongle supported by RTL-SDR along with https://github.com/MalcolmRobb/dump1090 or similar will allow this, but bear in mind that something like this should really not be used in any situation where flight safety depends on it.

That uses a google map which is nice, but I'd prefer something offline.

Should be very easy to swap the google map out for something offline. You can still use the remaining 99% of the tool which does the receiving/decoding/interpreting of the signals.

If you're only showing the area around the airport, even a static PNG of the map would work, would it not? Obviously you'd need to figure out the offsets, etc to draw the planes "on top" of the image (if we're talking about an HTML page).

Is there a site that offers truly open data, as in a download of all their collected historic data under a open license and without other restrictions (like having to query an API)?

Adsbexchange.com

Not open data :(

> for non-commercial use, all of this data is freely accessible to anyone!

> Any commercial users are required to license the data from ADSBexchange, contact here for terms.

Commercial use is a thing very hard to define so I avoid that even for personal projects (which could be consider advertisements for my commercial offers).

One of the reasons I love HN!!! Nicely written and informative post, cheap and practical stuff, lots of interesting links, comments with extra info... I’m so definitely building a receiver with my spare RPi3.

Interesting tidbit from the article—apparently flightradar24 doesn’t show business jets or military planes.

I was able to see our state police helicopters a while ago. The state has them marked private now.

If you're interested in that data, https://www.adsbexchange.com will show it. They also have filters available to only show things like Military or "Interesting" aircraft.

I can confirm it does not show the F15s that routinely fly over my house. But I see business jets all the time, no problem.

Those may be running with their transponder off?

For FR24, commercial bizjets are shown (i.e. those operated for charter). It's only privately owned and operated bizjets that can be hidden if the owner requests it.

I always thought it would be interesting to package all of this up and sell it to small operators. For example, a flight school could deploy a small scale RTL-SDR based ADS-B/MLAT system for tracking of their aircraft. The geographic area required to cover would be relatively small. Perhaps a 50 nm radius around the base. Of course they could also just fill in the gaps of something like Flightradar or ADS-B exchange but sometimes it’s nice to own your infrastructure.

Flight Aware offer a conceptually similar product (i.e. aimed at small operators/FBOs that want to track aircraft) but it uses data from their network rather than needing you to setup your own gear: https://www.flightaware.com/commercial/global

For a more DIY approach, there's these two: http://www.coaa.co.uk/planeplotter.htm http://www.virtualradarserver.co.uk/Default.aspx

Relevant talk on getting data live from the sky with Node: https://www.dotconferences.com/2017/12/thomas-watson-getting...

Flightview also offers an enterprise account for those running an ADS-B ground station and reporting it with their software.

https://flightaware.com/adsb/piaware/build

Someone put ADS-B on a satellite a few years ago, it looks like this has been done more recently as well:

https://www.radarbox24.com/blog/space-based-ads-b

AFAIK at least in Europe we are exactly in the process of moving ADS-B receivers in satellites in a large scale fashion to replace the current system based on ground units. I was talking with a control tower worker a few days ago and this is what he said, additionally a few months ago as the author of dump1090 I was approached by the company he mentioned that tried to hire me. So it looks like it's true.

Similar open source thing exists for gliders: https://www.glidernet.org It uses flarm data, which is received by many enthusiasts. Has been on a rise the last few years

Blog post could have included a link to https://www.flightradar24.com/ at least in the first paragraph. Can't find any link in the post at all.

I’m assuming there is more to it than just the radio data? In FR you can see planes everywhere, including thousands of miles off shore.

My guess is that FR24 just looks up the flight path from the flight number, and then once an airplane goes “off the radar” it just assumes it goes the shortest/great circle path towards its destination airport - at which point it will again be in a “known” spot? If this is how it’s done then one should see lots of planes approaching e.g the US east coast suddenly “shift” from their estimate position to their transponder positions, as they are picked up by receivers.

But you can see for yourself aeroplanes far over the ocean clearly not following a great circle route, presumably avoiding weather patterns.

Interesting. So how does that work in FR24? If there was a service to get this data over long distances, then all these short range receivers would be unnecessary. So something is missing in “how does FR24 work” when it comes to that data.

Probably satellite ADS-B receivers like from: https://en.wikipedia.org/wiki/Aireon

If that's what happens - does that mean that suddenly FR24 won't need all this data crowdsourcing?

Yes, it looks like it does just estimate the great circle route. The lines are all dashed for the planes over the ocean, starting a few hundred miles offshore.

This may change soon -- at least for the North Atlantic -- now that Aireon is using satellites to pick up ADS-B data. It's just a question of whether or not this info gets included in the FAA's ASDI feed.

Glad to see english version of the habr slowly getting traction.

Good improvement on them. They had interesting articles from time to time, from various domains (security, gamedev, DYI, management, work-life balance, work migration, science, etc). Opening to the international audience can only be beneficial for them, and the audience.

In North America ADS-B is pretty rare except on the coasts where international flights pass through more frequently. If you are not on the coast and look at the logs of your flightradar24 receiver you will see that 99% of the traffic are MLAT rf direction finding logs from mode-S transmissions with no GPS data used. But it's still easier to call it an "ADS-B" receiver because no one knows that MLAT is.

Flightradar24 has a nice interface and apps but it is CENSORED. Not all airplanes transmitting ADS-B are visible there.

Fortunately there is https://www.adsbexchange.com which offers unfiltered data. You can set up a receiver so that it runs dump1090 separately and forwards it to both using Beast protocol. You can also participate in adsbexchange M-LAT.

I started checking Flightradar24 after seeing a few planes circle above my office building one day. Never knew that transponder data was so accessible!

Check opennav.com whether there’s a waypoint at your location. There probably is, as a reference point for the hold pattern (if it was a hold). Just enter a nearby airport and then scroll down to the waypoint map.

You'll be surprised how much data you can easily grab out of thin air, if you probe the right frequency.

Reminds me of this DIY article: http://jeremybmerrill.com/blog/2016/01/flyover.html

HN thread here: https://news.ycombinator.com/item?id=10969447

They surely get data from other sources too. You can track planes flying across the ocean, where they get that data from?

Satellites, radar, interpolation up to 120 minutes, and receivers on islands.

https://www.flightradar24.com/blog/the-evolution-of-flightra...

https://www.flightradar24.com/blog/over-the-ocean-24-hours-o...

https://www.flightradar24.com/blog/tracking-flights-with-sat...

Thanks!

And what do they do above oceans? Interpolate? Or are there fallback sources of flights positions?

Iridium has a new service (Aireon) piggybacking off of its new satellite constellation that will relay ADS-B data from over the ocean.

This article suggests that positions are estimated when the aircraft isn’t in a coverage area. https://thepointsguy.com/2017/09/how-flight-tracking-sites-w...

It’s also worth noting that FlightAware has partnered with Aireon (owned by Iridium according to Wikipedia) to put ADSB receivers on satelites that were launched with Iridum’s NEXT satelite constellation in low-earth orbit. Sounds like that data is not yet included in the free data FlightAware provides on its website, but is available commercially. https://flightaware.com/commercial/aireon

You know what would be a fun experiment with this:

Would be to specifially watch all the planes that fly in and out of a large notable event; such as the superbowl, or davos, g-20 summit etc - and see where all thise private jets come from to get to that event...

I've seen people doing this on Twitter. With yachts, too, IIRC.

That exists! https://www.flightradar24.com/blog/watch-the-massive-exodus-...

.. or a small war. https://yorksranter.wordpress.com/2007/07/27/ex-viktor-bout-...

People are definitely doing this, also codified in this paper: http://www.cs.ox.ac.uk/files/9919/eurosnp.pdf (Inferring Confidential Corporate Mergers and Government Relations from Air Traffic Communication)

See also the other article currently on the front page of HN re Space Based ADS-B: https://news.ycombinator.com/item?id=19187745

Does something like flightradar24 exist for trains?

The only API i found exclude all freight trains. (Netherlands) https://spoorkaart.mwnn.nl/

It updates position and transmits once per second. I wonder if that makes it useful as a homing signal for a missile. Or perhaps the position resolution isn't close enough for that?

GPS isn't really precise enough for that and targeting civilian aircraft is easy anyway; this isn't much of an additional attack vector, IMO.

I suppose the benefit of knowing where everything is a security plus. Watching 9/11 documentaries, it was surprising how many aircraft the controllers couldn't account for.

(Though this does seem spoofable.)

Not so useful for a plane traveling at 800 km/h. And it's transmitted with radio so anyone can pick it up without internet. But if you want to fire something at a plane there are much easier and cheaper things to use from the ground.

I didn't mean the internet part...ADS-B in general.

I don’t know why, but I’m going to set up a station. Just ordered a Pi to setup pihole, might as well track flights around me too.

It's worth pointing out that you can get a free ADS-B receiver from sites like Flightradar24 or Flightaware.

The hardware is often proprietary, but they must allow you to re-purpouse the data received by the antenna (it's public domain).

The article goes over this.

I'm really not a carefull reader...

Wow! I had no idea this is how they did it. Very cool!

Then how are they not able to find airplanes like mh370...?

The coverage is not global - there are gaps over the oceans and in remote areas (as the article states, it mostly requries unobstructed direct line of sight).

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