I wrote a rather elaborate demo that tracks aircraft using Redis and Node.js. It does this by receiving aircraft transponder broadcasts and shoving them into an event stream in Redis.
There is no Internet involved in receiving these broadcasts. Instead, a hardware device called a software-defined radio (SDR) receives these broadcasts from the air and converts them into useful data that we can use. Which is pretty dang cool!
This repo contains the code and instructions you need to get it up and running for yourself.
I also have a talk about this. If you want to check out the slides, they're in here too.
This demo uses a software-defined radio. Despite the use of the word software in its name, software-defined radio is actually a hardware device. So, you'll need to buy an SDR and an antenna to use this demo. No worries, SDRs are cheap.
Here's the load-out I like to use. It includes the SDR dongle and an antenna specifically designed for picking up aircraft transponder broadcasts.
- RTL SDR: https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Defined/dp/B0CD745394/
- ADS-B Antenna: https://www.amazon.com/1090MHz-Antenna-Fiberglass-SMA-Male-Extension/dp/B09BQ4H26L/
If you want something cheaper and more general-purpose, and this is probably a better choice, some bundles include the same SDR and some more flexible antennas. This is a good way to go if you want to do other things with your SDR. Which will happen.
You can also make your own antenna if you are ambitious. I'll leave that up to your own googling.
If you choose to make an antenna or to use the kit above, you'll want both legs of the antenna extended/cut to a length of ~69mm. Arrange them so that they are in a line, 180 degrees apart. This, in radio terms, is called a dipole.
Regardless of which antenna option you go with, you'll want to mount it vertically as this matches the way they are mounted on aircraft. Here's a picture of a homemade antenna (not mine) mounted vertically in an attic (not mine):
Thanks for the picture, random Internet stranger!
Installing SDR software can be a bit fiddly. You've been warned. That said, it has gotten easier over the years. You'll need two pieces of software to make this code work—besides, like, Node.js and stuff: the RTL SDR drivers, and dump1090.
These drivers allow your computer to talk to the SDR. And they provide lots of interesting command-line tools to boot. You'll need this to do, well, anything with your SDR.
sudo apt update
sudo apt install rtl-sdrbrew install rtl-sdrYou can download the RTL SDR drivers and tools from https://ftp.osmocom.org/binaries/windows/rtl-sdr/. They are built weekly so get the latest one for your platform—probably the 64-bit one. The download is simply a .ZIP file full of .EXE and .DLL files. Put these files in a folder somewhere on your system and add that folder to your PATH to get it working.
Details on the drivers themselves can be found at https://osmocom.org/projects/rtl-sdr/wiki/Rtl-sdr.
Regardless of your platform, testing is the same. Plug in your SDR and run the following command:
rtl_testYou should get back something like:
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 00000001
Using device 0: Generic RTL2832U OEM
Detached kernel driver
Found Rafael Micro R820T tuner
Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
[R82XX] PLL not locked!
Sampling at 2048000 S/s.
Info: This tool will continuously read from the device, and report if
samples get lost. If you observe no further output, everything is fine.
Reading samples in async mode...
Allocating 15 zero-copy buffers
lost at least 12 bytes
Hooray! Your drivers are working. Press Ctrl-C to stop and go to the next step.
Dump1090 is software that uses an RTL SDR to listen to aircraft transponder broadcasts, present them to the user, and make them available over a socket connection. The code in this repo uses that socket connection to read the broadcasts.
sudo apt install dump1090-mutabilityYou might be asked if you want to install this so that it always runs. I've only ever said no.
brew install dump1090-mutabilityWindows has a lot of ports of dump1090. I like to use this one: https://github.com/MalcolmRobb/dump1090.
Just download the .ZIP file in the root of the repository—yes, it's really 10 years old—and unzip it into a folder of your choice. From there, you can just run it from that folder or, if you prefer, add it to your path.
You should now be able to run dump1090 using the following command:
dump1090 --net --interactiveIf you installed to Linux, you'll need to run this instead:
dump1090-mutability --net --interactiveIf you have your antenna attached, aircraft should start showing up. Here's some that I found today while writing this README:
Hex Mode Sqwk Flight Alt Spd Hdg Lat Long RSSI Msgs Ti/
-------------------------------------------------------------------------------
AD4C2A S -39.6 3 1
A097CE S 40000 -32.5 11 0
06A1DA S 47000 -33.4 7 0
A71ABB S 7143 43000 476 272 -33.1 18 1
A280FE S 40000 443 299 40.346 -83.589 -35.5 5 0
A1FF90 S 4000 230 294 39.920 -83.152 -28.2 13 0
A59398 S 1512 AAL464 34975 472 082 40.013 -82.266 -27.4 55 0
A05544 S 43000 474 107 40.163 -82.640 -29.5 21 2
A66312 S 1200 OSU51 1700 90 270 40.091 -83.082 -25.2 49 0
A537ED S 6646 RPA4723 31000 439 103 39.867 -82.767 -28.0 100 0
A05AAC S 6616 UCA4824 31000 431 102 39.984 -82.297 -23.8 39 0
A16B47 S 41000 491 045 40.486 -83.588 -31.7 39 1
A69939 S 1546 EJA524 5925 240 275 39.909 -82.957 -25.0 64 0
AC0B74 S SWA4635 36000 455 267 40.523 -83.089 -28.6 94 0
A0B990 S 6036 40000 423 322 39.488 -83.482 -26.7 56 0
C07C7A S 7276 37000 467 053 40.124 -82.966 -19.3 56 0
Now that we have the fiddly bits working, we can get the demo running. The demo itself is made up of four components: the Radio Ingestor, the Flight Server, the Flight UI, and Redis.
graph LR
subgraph "Atlanta"
ANT1{Antenna} --> SDR1((RTL SDR)) --> DMP1[dump1090] --> ING1("Radio Ingestor")
end
subgraph "Columbus"
ANT2{Antenna} --> SDR2((RTL SDR)) --> DMP2[dump1090] --> ING2("Radio Ingestor")
end
subgraph "Denver"
ANT3{Antenna} --> SDR3((RTL SDR)) --> DMP3[dump1090] --> ING3("Radio Ingestor")
end
ING1 --> RED[Redis]
ING2 --> RED
ING3 --> RED
RED <--> SRV("Flight Server")
subgraph "Consumer"
SRV <--> WEB("Flight UI")
end
The purpose of the Radio Ingestor is to take transponder broadcasts and write them to a Redis event stream. It is designed so that multiple instances can run at the same time feeding aircraft spots into Redis from multiple, geographically dispersed locations.
The Flight Server consumes the event stream, enriches it, and saves current flight statuses to Redis. It also publishes the enriched data as a WebSocket and provides simple HTTP APIs to query aircraft status and stats.
The Flight UI presents flight data to the end user providing both map and detail views. It is designed to work alongside the Flight Server and is useless without it.
In a dedicated window, launch dump1090 with one of the following commands:
dump1090 --net --interactive # for Mac or Windows
dump1090-mutability --net --interactive # for LinuxThe --net option tells dump1090 to publish transponder broadcasts on port 30003. The --interactive option just makes it prettier.
Now, from the root of this repo run:
docker compose up --buildThis will download Redis, build all the components, and start them up with defaults that will work. No fuss. No muss.
Once it's started, point your browser at http://localhost:8000 and watch the aircraft move about.
Redis is where we're storing our aircraft spots. If you're not going with the quickstart, you'll need Redis somewhere. You can either install it locally, use Docker, or use Redis Cloud.
-
To install Redis locally, follow the instructions at https://redis.io/docs/latest/operate/oss_and_stack/install/install-stack/.
-
To use Docker, run the following command:
docker run -d --name redis-stack-server -p 6379:6379 redis/redis-stack-server:latest- To use Redis Cloud, sign up for a free account at https://cloud.redis.io/.
You might also want to snag Redis Insight so you can see what Redis is doing. You can find that on the App Store, the Microsoft Store, or directly from Redis.
You'll need an existing Redis instance to do this. This might be local, but will probably be a Redis Cloud instance.
Before you run the Radio Ingestor, it must be configured. Details are in the the sample.env file in the radio-ingestor folder. However, the tl;dr is:
cd radio-ingestor
cp sample.env .envThen edit the Redis options in the .env file to point to your Redis instance.
To run the Radio Ingestor you can just use Docker:
cd radio-ingestor
docker compose up --buildIf you'd rather run it using Node.js directly, then make sure you have Node.js installed and run the following commands:
cd radio-ingestor
npm install
npm run build
npm startIf you'd like to run it in dev mode instead you can skip the build:
cd radio-ingestor
npm install
npm run devYou should be able to see an event stream in Redis—using Redis Insight, of course—populating with aircraft transponder events.
You'll need an existing Redis instance to do this. This could be a local instance of Redis, but will probably be a shared instance like Redis Cloud. This instance should be fed by one or more instances of a Radio Ingestor. Technically, this'll work even if the instance isn't being fed, but it won't be very interesting. Nothing in. Nothing out.
Before you run the Flight Server, it must be configured. Details are in the sample.env file in the flight-server folder. However, the tl;dr is:
cd flight-server
cp sample.env .envThen edit the Redis options in the .env file to point to your Redis instance.
To run the Flight Server you can just use Docker:
cd flight-server
docker compose up --buildIf you'd rather run it using Node.js directly, then make sure you have Node.js installed and run the following commands:
cd flight-server
npm install
npm run build
npm startIf you'd like to run it in dev mode instead you can skip the build:
cd flight-server
npm install
npm run devIf these instructions seem familiar, that's because I copied them directly from the Radio Ingestor instructions. It's the same process.
Regardless, if you look in Redis Insight, you should see a lot more keys including JSON documents for each of the aircraft spotted; T-Digests gathering stats about altitude, velocity, and climb; a HyperLogLog counting unique aircraft; and a humble little string counting the number of messages received.
The Flight UI does not need to be configured. It's all ready to go. However, it is hard-coded to look for the Flight Server on localhost:8080 and to expose itself on port 8000 when run in developer or preview mode. Once you compile it, you can server up the files on any port you'd like.
At some point, I'd like to make the Flight Server host and port configurable. But this is what we have for now.
To run the Flight Server you can just use Docker. Docker will compile the site and then host it internally on an NGINX instance:
cd flight-ui
docker compose up --buildIf you'd rather run it using Node.js and vite, then make sure you have Node.js installed and run the following commands:
cd flight-ui
npm install
npm run build
npm run previewIf you'd like to run it in dev mode instead you can skip the build:
cd flight-ui
npm install
npm run devIn any of these cases, point your browser at http://localhost:8000 and you should see an aircraft map.
That's pretty much it. If you see a bug, a typo, or some small improvements, feel free to send a PR. If you see something big or would like to make major improvements, reach out and let's discuss it.
I hope you find this fun and instructive. Happy spotting!