QuentinC/Dump1090

A simple ADS-B (Automatic Dependent Surveillance - Broadcast) receiver, decoder and web-server. Needs a RTLSDR USB-stick and/or SDRplay device.

Dump1090

A simple ADS-B (Automatic Dependent Surveillance - Broadcast) receiver, decoder and web-server.
It requires a RTLSDR USB-stick and Osmocom's librtlsdr.

This Mode S decoder is based on the original Dump1090 by Salvatore Sanfilippo which is here.
Most of the text below is written by him. In this README.md file, I've mostly fixed the MarkDown and added some more references and screen-shots. But in the source-code I've done a lot of changes.

ADS-B basics:

• A YouTube video explaining it's basics and motivation.
• A detailed technical description by professor Junzi Sun.
• Or as a PDF in this repo.

The main features of Dump1090 are:

• Robust decoding of weak messages, with Dump1090 many users observed improved range compared to other popular decoders.
• Network support: TCP port 30003 stream (MSG5 ...), Raw packets and HTTP.
• An embedded Mongoose HTTP server that displays the currently detected aircrafts on an OpenStreet Map.
  Hopefully WebSocket support is coming soon (JScript and Json transfer is rather chatty).
• Single bit errors correction using the 24 bit CRC.
• Ability to decode DF11, DF17 messages (Downlink Format).
• Ability to decode formats like DF0, DF4, DF5, DF16, DF20 and DF21 where the checksum is XORed with the ICAO address by brute forcing the checksum field using recently seen ICAO addresses.
• Decode raw IQ samples from file (using the --infile bin-file command line option).
• Interactive command-line-interface mode where aircrafts currently detected are shown as a list refreshing as more data arrives. Planes that haven't been seen last 60 seconds are removed from the list (option --interactive-ttl sec to change).
• CPR (Compact Position Reporting) coordinates decoding and track calculation from velocity.
• TCP server streaming and receiving raw data to/from connected clients
  (options --net or --net-only).

While from time to time I still add / fix stuff in my fork, I target minimalism in this implementation.
However there is a much more feature complete fork available, developed by Malcolm Robb.

Building

• Using GNU-make, type:
  • c:\dev\Dump1090> make -f Makefile.Windows CC=cl (or CC=clang-cl).
• Or using Visual Studio tools:
  • c:\dev\Dump1090> msbuild -p:Configuration=Release -p:Platform="x86" Dump1090.sln.
  • or start the Visual Studio IDE, open Dump1090.sln, right-click and Build Solution.

(assuming you have downloaded this package to c:\dev\Dump1090).

Normal usage

To capture traffic directly from your RTLSDR device and show the captured traffic on standard output, just run the program without options at all:

c:\dev\Dump1090> dump1090

To use a SDRplay device, the option --device must be used. Like:

c:\dev\Dump1090> dump1090 --device sdrplay0

But these devices does not work correctly yet.

Example output:

Tuned to 1090.000 MHz. Gain reported by device: AUTO.
*8d479e84580fd03d66d139c1cd17;
CRC: c1cd17 (ok)
DF 17: ADS-B message.
  Capability     : 5 (Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is on airborne))
  ICAO Address   : 479e84
  Extended Squitter  Type: 11
  Extended Squitter  Sub : 0
  Extended Squitter  Name: Airborne Position (Baro Altitude)
    F flag   : even
    T flag   : non-UTC
    Altitude : 2125 feet
    Latitude : 7859 (not decoded)
    Longitude: 53561 (not decoded)
...

To only output hexadecimal messages:

c:\dev\Dump1090> dump1090 --raw

Example output:

Tuned to 1090.000 MHz. Gain reported by device: AUTO.
*8d47c1abea040830015c087c6a4b;
*8d479e84990c5607200c8319b311;
*8d479e84580fd04278cda6bd6d32;
...

To run the program in interactive mode: c:\dev\Dump1090> dump1090 --interactive

To run the program in interactive mode, with networking support and connecting to your browser to http://localhost:8080, use this command:

c:\dev\Dump1090> dump1090 --interactive --net

It will present live traffic to the Web-browser:

and the console:

In this interactive mode there is a more compact output. Where the screen is refreshed up to 4 times per second displaying all the recently seen aircrafts with some additional information such as flight number, altitude, speed, heading and position. All items extracted from the received Mode S packets. Except the above Messages and last Seen.

Using files as source of data

To decode data from file, use:

c:\dev\Dump1090> dump1090 --infile file.bin

The binary file should be created using rtl_sdr like this (or with another program that is able to output 8-bit unsigned IQ samples at 2 MHz sample rate):

c:\dev\OsmoCom> rtl_sdr -f 1090M -s 2000000 output.bin

In the above example, rtl_sdr with AUTO gain is used. Use rtl_sdr -g 50 for a 50 dB gain. A need to experiment with the gain depends on the tuner. But in my expirence, AUTO gain works best (--gain 0).

This is not needed when calling Dump1090 itself.

It is possible to feed the program with data via standard input using the --infile option with - as argument.

When a aircraftDatabase.csv is present and used with a .bin-file, it can show output like:

c:\dev\Dump1090> dump1090 --infile testfiles\modes1.bin
...
*5d4d20237a55a6;
CRC: 7a55a6 (ok)
DF 11: All Call Reply.
  Capability  : Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is airborne)
  ICAO Address: 4d2023 (reg-num: 9H-AEM, manuf: Airbus)

*20000f1f684a6c;
CRC: 684a6c (ok)
DF 4: Surveillance, Altitude Reply.
  Flight Status  : Normal, Airborne
  DR             : 0
  UM             : 0
  Altitude       : 23375 feet
  ICAO Address   : 4d2023 (reg-num: 9H-AEM, manuf: Airbus)

Use option --database NUL (or --database - etc.) to avoid loading this huge (approx. 82 MByte) .CSV file.
The latest version is available from: http://opensky-network.org/datasets/metadata/

Additional options

Dump1090 can be used with other command line options to set a different gain, frequency, and so forth.
Full list of options use is shown using dump1090 --help or dump1090 -h.

A syntax like dump1090 --freq 1090.001M is possible for cheap RTLSDR devices with high frequency drift. But for most devices, this is not needed (due to the capture effect of the signal itself?).

Everything is not documented here ... obviously. For most users running dump1090 --interactive is probably best thing to do.

Reliability

By default Dump1090 tries to fix single bit errors using the checksum. Basically the program will try to flip every bit of the message and check if the checksum of the resulting message matches.

This is indeed able to fix errors and works reliably in my experience, however if you are interested in very reliable data, I suggest to use the --no-fix command line switch in order to disable error fixing.

Performances and detection

In my limited experience Dump1090 was able to decode a large number of messages even in conditions where I encountered problems using other programs. However no formal test was performed so I can't really claim that this program is better or worse compared to other similar programs.

If you can capture traffic that Dump1090 is not able to decode properly, drop me an email with a download link. I may try to improve the detection during my free time (this is just an hobby project).

Network server features

By enabling the networking support with --net, dump1090 starts listening for clients connections on port 30002 and 30001 (you can change both ports --net-X-port Y. See --help or -h for details).

• Port 30002 connected clients are served with data ASAP as they arrive from the device (or from file if --infile is used) in the raw format similar to the following:
  *8D451E8B99019699C00B0A81F36E;
  Every entry is separated by a simple newline (LF character, hex 0x0A).

• Port 30001 is the raw input port, and can be used to feed dump1090 with data in the same format as specified above, with hex messages starting with * and ending with a ; character.
  

So for instance if there is another remote Dump1090 instance collecting data it is possible to sum the output to a local Dump1090 instance with the help of NetCat or NCat:
nc remote-dump1090.example.net 30002 | nc localhost 30001

It is important to note that what is received via port 30001 is also broadcasted to clients listening to port 30002.

In general everything received from port 30001 is handled exactly like the normal traffic from RTL devices or from file when --infile is used.

If your feed Dump1090 with data from the internet, one can use this command to see on the console what's happening:

c:\dev\Dump1090> dump1090 --net-only --interactive

• Port 30003 connected clients are served with messages in SBS1 (BaseStation) format, similar to:
  

  MSG,4,,,738065,,,,,,,,420,179,,,0,,0,0,0,0
  MSG,3,,,738065,,,,,,,35000,,,34.81609,34.07810,,,0,0,0,0
  

  This can be used to feed data to various sharing sites without the need to use another decoder.

Antenna

Mode S messages are transmitted on the standard frequency of 1090 MHz. If you have a decent antenna you'll be able to pick up signals from aircrafts pretty far from your position, especially if you are outdoor and in a position with a good sky view.

You can easily build a very cheap antenna following these instructions. With this trivial antenna I was able to pick up signals of aircrafts 200+ Km away from me.

If you are interested in a more serious antenna or ADS-B equipment, check the following resources:

• GnuRadio Mode-S/ADS-B.
• Simple ADSB J-pole antenna.
• ADS-B / MLAT. Multilateration; using a Time Difference of Arrival (TDOA) calculation based on signals from several receivers (probably not cheap RTLSDRs).

Aggressive mode

With --aggressive it is possible to activate the aggressive mode that is a modified version of the Mode S packet detection and decoding. The aggresive mode uses more CPU usually (especially if there are many planes sending DF17 packets), but can detect a few more messages.

The algorithm in aggressive mode is modified in the following ways:

• Up to two demodulation errors are tolerated (adjacent entires in the magnitude vector with the same eight). Normally only messages without errors are checked.
• It tries to fix DF17 messages trying every two bits combination.

The use of aggressive mode is only advised in places where there is low traffic in order to have a chance to capture some more messages.

Debug mode

The Debug mode is a visual help to improve the detection algorithm or to understand why the program is not working for a given input.

In this mode messages are displayed in an ASCII-art style graphical representation, where the individial magnitude bars sampled at 2 MHz are displayed.

An index shows the sample number, where 0 is the sample where the first Mode S peak was found. Some additional background noise is also shown before the first peak to provide some context.

To enable debug mode and check what combinations of packets you can log, use dump1090 --help to obtain a list of available debug flags.

Debug mode includes an optional JavaScript output (frames.js) that is used to visualize packets using a web browser, you can use tools/debug.html to load and analyze the generated frames.js file: .

How this program works?

The code is very documented and written in order to be easy to understand.
For the diligent programmer with a Mode S specification at hand, it should be trivial to understand how it works.

The algorithms I used were obtained basically looking at many messages as displayed using a throw-away SDL program, and trying to model the algorithm based on how the messages look graphically.

How to test the program?

If you have an RTLSDR device and you happen to be in an area where there are aircrafts flying over your head, just run the program and check for signals.

If however you don't have an RTLSDR device, or if in your area the presence of aircrafts is very limited, you may want to try it with the sample file under the testfiles directory. Run it like this:

c:\dev\Dump1090> dump1090 <other-options> --ifile testfiles/modes1.bin

What is --strip mode?

A simple filter that will take raw 8-bit IQ samples on input and output a file missing the I/Q parts that were below the specified --strip level. And if those I/Q samples were below limit for at least 32 samples.
Can be used like: type big.bin | dump1090 --strip 25 > small.bin

The --strip mode was used to create e.g. testfiles/modes1.bin.

Contributing

Dump1090 was written during some free time during xmas 2012, it is an hobby project so I'll be able to address issues and improve it only during free time, however you are incouraged to send pull requests in order to improve the program. A good starting point can be the TODO list included in the source distribution.

Credits

Dump1090 was written by Salvatore Sanfilippo and is released under the BSD three clause license.