I’m not very familiar with the aviation jargon (see FAA’s ADS-B FAQ), but ADS-B is a next-gen system where aircraft are equipped with transponders that periodically broadcast their own positions and receive the reports from both other aircraft (direct air-to-air) as well as air-traffic control (ATC) ground transmitters.
There are two separate ADS-B radio bands: the commercial aviation (CA) is at 1090 MHz while the general aviation (GA) is at 978 MHz. If I can be permitted a gross generalization—the former corresponds to big commercial jets and the latter to small private aircraft.
Because ADS-B is designed to democratize airspace situational awareness (in contrast to the older setup, like from films, where a central air-traffic controller is coordinating all these aircraft that can’t see each other), we can buy cheap RF receivers to pick up and decode the messages being broadcast by aircraft and ground towers to get our own picture of the local airspace. This rabbit hole actually goes quite deep: FlightAware.com has built a business on crowdsourced ADS-B receivers. They will give you a networked ADS-B kit called FlightFeeder, for free, if you live in an area of sparse coverage.
Here’s one way to receive, log, and real-time visualize the traffic on either of these ADS-B bands using a USB radio receiver and some open-source software on a Mac.
Hardware & base software setup
Buy RTL-SDR. $25 kit on Amazon.
Optional: buy antennas. $20 Stratux DMURRAY14 kit.
$ brew install pkg-config cmake librtlsdr
Clone @mutability’s fork of dump1090 to collect and visualize commercial aviation (CA), which operates in the 1090 MHz band. (You’ll want this even if you’re only after general aviation (GA), which is on the 978 MHz band—our dump978 setup will use dump1090 for visualization.)
$ git clone https://github.com/mutability/dump1090.git $ cd dump1090 $ make -j4 # omit if you will only do dump978/GA
Start external webserver
If you’ve ever used the original dump1090 by @antirez: @mutability’s fork of dump1090 is architecturally different than the original. This fork writes a JSON file which has to be served by some external webserver.
First create a directory to store the parsed results in JSON:
$ mkdir public_html/data
Then start a webserver that hosts the
public_html directory. You have many choices but here’s a really simple one:
$ cd public_html && python -m SimpleHTTPServer 8090
This uses Python2 to serve the current directory’s contents: browse to http://127.0.0.1:8090/gmap.html to see an OpenStreetMap.
Now, an application like dump1090 or dump978 can put data inside this directory and the map will display it.
Run, log, and visualize dump1090
Finally, launch dump1090 and pipe its output to disk for logging:
$ ./dump1090 --write-json public_html/data >> log.txt
You should soon see aircraft showing up on the map:
dump1090 example output
Here’s some example lines from
log.txt: this is the standard output of dump1090. (For debugging, looking at the last few lines of
$ tail -f log.txt can help.)
*8dab77ee99459081c0084e933a70; CRC: 000000 RSSI: -22.7 dBFS Score: 1400 Time: 26780.42us (phase: 300) DF 17: ADS-B message. Capability : 5 (Level 2+, airborne) ICAO Address : ab77ee Extended Squitter Type: 19 Extended Squitter Sub : 1 Extended Squitter Name: Airborne Velocity EW status : Valid EW velocity : -399 NS status : Valid NS velocity : -13 Vertical status : Valid Vertical rate src : 0 Vertical rate : 64 HAE/Baro offset : 1925 ft *8da923cf99157717c004477716b8; CRC: 000000 RSSI: -30.7 dBFS Score: 1400 Time: 53030.33us (phase: 240) DF 17: ADS-B message. Capability : 5 (Level 2+, airborne) ICAO Address : a923cf Extended Squitter Type: 19 Extended Squitter Sub : 1 Extended Squitter Name: Airborne Velocity EW status : Valid EW velocity : -374 NS status : Valid NS velocity : 189 Vertical status : Valid Vertical rate src : 0 Vertical rate : 0 HAE/Baro offset : 1750 ft
Note that the
Time field above corresponds to microseconds since the application started. This provides a simple way of timestamping each observation, assuming you can tell when the application started.
Clone and build @mutability’s dump978 repository to collect general aviation beacons, which operate in the 978 MHz band. Don’t run this when in the same directory as
dump1090—you almost never want a git repository inside another git repository.
$ git clone https://github.com/mutability/dump978.git $ cd dump978 $ make -j4 $ cp -r /PATH/TO/dump1090/public_html . $ mkdir -p public_html/data
The last two lines copy dump1090’s webapp to the dump978 directory and (re)creates a
Start external webserver
Following the same process as dump1090, we can start a webserver using plain Python2. We will choose a different port to avoid conflicts with the dump1090 webapp.
$ cd public_html && python -m SimpleHTTPServer 8978
Open a browser tab to http://127.0.0.1:8978/gmap.html.
Run, log, and visualize dump978
dump978 is a little different from dump1090, in that dump978 accepts binary samples output by
rtl_sdr, rather than doing this behind-the-scenes:
$ rtl_sdr -f 978000000 -s 2083334 - | ./dump978 | tee --append log.txt | ./uat2json public_html/data
Soon, you should start seeing GA traffic in the web browser. dump978’s
uat2json will update the webapp’s data once a second.
Caveat! The above logs
dump978’s output to
log.txt, but without timestamps, which might severely limit the use of this data! If you have
brew install moreutilson macOS), I recommend the following:
$ rtl_sdr -f 978000000 -s 2083334 - | ./dump978 | ts '[%Y-%m-%d.%H.%M.%.S%z]' | tee --append log.txt | cut -d' ' -f2- | ./uat2json public_html/data
This will prepend a timestamp, followed by a space, like
[2016-11-126.96.36.199.117154-0500], before each line. That
teewrites such timestamped data to a file, but then the
cutstrips the timestamps before sending the original result to
uat2json. (Caveat the second: that strftime specifier,
[%Y-%m-%d.%H.%M.%.S%z]could be invalid on some systems, check!)
Beware: both browser windows (dump1090’s and dump978’s) will say “dump1090”, since we just copied dump1090’s webapp and are dumping 978 MHz data into it. The only difference is the port number in the URL.
dump978 example output
Here are some lines from the
log.txt file produced by dump978:
-10a3a09839220f88e80218d911a83a202f00000000000000000000000019c0000000;rs=1; -10a3a0983921cf88e85e18d911a83a001f00000000000000000000000019c0000000; 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;rs=32; +3916598895a4bfa000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000;rs=32; -0b28c2ef38db29868efe279641940cc01105c4e6c4e6c40a82700300000000000000;rs=2; -00a3a0983921b388e88418d911a83a001900;
dump978 makes available a
uat2txt executable, which produces the following when fed in the above:
$ cat log.txt | ./uat2txt HDR: MDB Type: 2 Address: A3A098 (ICAO address via ADS-B) SV: NIC: 9 Latitude: +40.1717 Longitude: -83.7378 Altitude: 8900 ft (barometric) N/S velocity: -105 kt E/W velocity: 115 kt Track: 132 Speed: 155 kt Vertical rate: -64 ft/min (from geometric altitude) UTC coupling: yes TIS-B site ID: 0 AUXSV: Sec. altitude: 9275 ft (geometric) HDR: MDB Type: 2 Address: A3A098 (ICAO address via ADS-B) SV: NIC: 9 Latitude: +40.1710 Longitude: -83.7368 Altitude: 8900 ft (barometric) N/S velocity: -105 kt E/W velocity: 115 kt Track: 132 Speed: 155 kt Vertical rate: 0 ft/min (from geometric altitude) UTC coupling: yes TIS-B site ID: 0 AUXSV: Sec. altitude: 9275 ft (geometric) UPLINK: Site Latitude: +40.1395 (possibly invalid) Site Longitude: -83.9640 (possibly invalid) UTC coupled: yes Slot ID: 14 TIS-B Site ID: 10 INFORMATION FRAME: Length: 181 bytes Type: 0 (FIS-B APDU) FIS-B: Flags: Product ID: 413 (Generic Textual Data Product APDU Payload Format Type 2) - Text (DLAC) Product time: 19:00 Report type: TAF Report location: KMUI Report time: 301900Z Text: 3019/0101 27009KT 9999 FEW050 FEW200 QNH2990INS BECMG 3120/3121 18006KT 9999 BKN050 QNH2984INS BECMG 3123/3124 15006KT 8000 -SHRA BKN030 OVC150 QNH2984INS TX30/3119Z TN15/3110Z LAST NO AMDS AFT 3105 NEXT 3111= UPLINK: Site Latitude: +40.1395 (possibly invalid) Site Longitude: -83.9640 (possibly invalid) UTC coupled: yes Slot ID: 31 TIS-B Site ID: 10 HDR: MDB Type: 1 Address: 28C2EF (TIS-B track file address) SV: NIC: 6 Latitude: +39.9769 Longitude: -85.3885 Altitude: 14800 ft (barometric) N/S velocity: 400 kt E/W velocity: 96 kt Track: 13 Speed: 411 kt Vertical rate: 0 ft/min (from barometric altitude) UTC coupling: no TIS-B site ID: 1 MS: Emitter category: No information Callsign: unavailable Emergency status: No emergency UAT version: 2 SIL: 2 Transmit MSO: 32 NACp: 7 NACv: 0 NICbaro: 0 Capabilities: Active modes: Target track type: true heading AUXSV: Sec. altitude: unavailable HDR: MDB Type: 0 Address: A3A098 (ICAO address via ADS-B) SV: NIC: 9 Latitude: +40.1707 Longitude: -83.7364 Altitude: 8900 ft (barometric) N/S velocity: -105 kt E/W velocity: 115 kt Track: 132 Speed: 155 kt Vertical rate: 0 ft/min (from geometric altitude) UTC coupling: yes TIS-B site ID: 0