ADS-B / 978 Integration

DragonSync can ingest aircraft data from a local readsb instance via HTTP and convert it to CoT for TAK/ATAK.

Status: Experimental. This is currently a multi-step and somewhat manual process.

Overview

readsb (SDR → 1090/978 MHz) → HTTP API → DragonSync → CoT

DragonSync polls the readsb HTTP API and builds CoT messages per aircraft with:

• Position, altitude (geometric/barometric), speed, track
• Richer remarks (hex, callsign, squawk, registration, category, on-ground flag)
• CE/LE accuracy derived from NACp/NACv when available

SDR Considerations

At the moment, only one SDR-driven role can use the same RF front-end at once:

Configuration	Use Case
Single SDR (DragonSDR)	Either drone detection OR ADS-B, not both simultaneously
Multiple SDRs	Dedicated SDR for drones + separate SDR for ADS-B

Single SDR

You can either:

• Run DJI/FPV-related tasks, or
• Run readsb for ADS-B / 978

Switching roles means stopping one and starting the other. This is best used for demo/experiment modes.

Multiple SDRs (Recommended)

For continuous drone + aircraft coverage:

• One SDR path for drone detection (DJI / RID)
• Another SDR (RTL-SDR, second DragonSDR, etc.) for ADS-B / 978 with its own readsb instance

You can run readsb with a different device selection and still point DragonSync at its API.

---

Setup

1. Start readsb

Pluto / DragonSDR Example

Using the DragonSDR in Pluto-compatible mode via SoapySDR:

sudo readsb \
  --device-type soapysdr \
  --soapy-device="driver=plutosdr" \
  --freq=1090000000 \
  --no-interactive \
  --write-json=/run/readsb \
  --write-json-every=1 \
  --json-location-accuracy=2 \
  --net-bind-address=0.0.0.0 \
  --net-api-port=8080 \
  --soapy-enable-agc \
  --sdr-buffer-size=128

RTL-SDR Example

sudo readsb \
  --device-type rtlsdr \
  --freq=1090000000 \
  --no-interactive \
  --write-json=/run/readsb \
  --write-json-every=1 \
  --json-location-accuracy=2 \
  --net-bind-address=0.0.0.0 \
  --net-api-port=8080

Key Options

Option	Description
--freq=1090000000	1090 MHz for standard ADS-B
--freq=978000000	978 MHz for UAT (US only)
--net-api-port=8080	HTTP API port
--device-type	soapysdr, rtlsdr, etc.
--soapy-device	SoapySDR device string

2. Verify readsb

Test the HTTP API:

curl -s http://127.0.0.1:8080/?all_with_pos | jq '.aircraft | length'

You should see a count of aircraft with positions. If you see 0 or an error, readsb isn't receiving data.

3. Configure DragonSync

Add to your config.ini:

[SETTINGS]

# ADS-B / UAT aircraft ingestion
adsb_enabled = true
adsb_json_url = http://127.0.0.1:8080/?all_with_pos

# Optional altitude gates (feet). 0 = disabled.
adsb_min_alt = 0
adsb_max_alt = 0

Altitude Filtering

You can filter aircraft by altitude:

# Only show aircraft below 10,000 feet
adsb_max_alt = 10000

# Only show aircraft above 1,000 feet (ignore ground traffic)
adsb_min_alt = 1000

# Both: 1,000 to 10,000 feet
adsb_min_alt = 1000
adsb_max_alt = 10000

Set to 0 to disable filtering.

---

How It Works

1. DragonSync polls adsb_json_url once per poll_interval
2. Expects readsb-style JSON with an aircraft array
3. For each aircraft with a valid position:
   • Builds a CoT message with position, altitude, speed, track
   • Includes hex code, callsign, squawk, registration, category
   • Derives accuracy (CE/LE) from NACp/NACv when available
4. Outputs CoT via configured TAK server or multicast

CoT Mapping

readsb Field	CoT Element
hex	UID suffix
lat, lon	Point position
alt_geom or alt_baro	HAE (converted to meters)
gs	Speed (converted to m/s)
track	Course
flight	Callsign in remarks
squawk	Squawk in remarks
category	Aircraft category in remarks
nac_p, nac_v	CE/LE accuracy

---

MQTT Output

To publish aircraft data to MQTT, you must enable both MQTT and aircraft publishing in config.ini:

mqtt_enabled = true
mqtt_aircraft_enabled = true
mqtt_aircraft_topic = wardragon/aircraft

Aircraft are then published to the configured topic (default: wardragon/aircraft):

{
  "icao": "A12345",
  "callsign": "UAL123",
  "registration": "N12345",
  "lat": 39.1234,
  "lon": -77.5678,
  "alt": 35000,
  "speed": 450,
  "track": 270,
  "squawk": "1200",
  "category": "A3",
  "on_ground": false,
  "rssi": -8.5,
  "track_type": "aircraft"
}

See mqtt-schema.md for the complete field reference.

Signal Strength (RSSI)

The rssi field contains signal strength from readsb, measured in dBFS (decibels relative to full scale), not dBm.

Value	Meaning
0 dBFS	Maximum signal (ADC saturation)
-10 dBFS	Very strong signal
-20 dBFS	Good signal
-30 dBFS	Weak signal

Important notes:

• dBFS is relative to the SDR's ADC, not absolute power
• Values depend on SDR gain settings
• For multi-kit triangulation, all kits should use similar gain settings
• rssi may be null if readsb doesn't provide it (older versions or certain configurations)

---

Troubleshooting

Issue	Solution
No aircraft in ATAK	Verify curl http://127.0.0.1:8080/?all_with_pos returns aircraft
readsb not starting	Check SDR device permissions, antenna connection
Only some aircraft appear	Enable /?all_with_pos not just /? which requires positions
High CPU usage	Increase poll_interval in config

Common readsb Issues

Permission denied on SDR:

# Add udev rules for RTL-SDR
sudo cp rtl-sdr.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules

SoapySDR device not found:

# List available devices
SoapySDRUtil --find

---

Frequency Reference

Frequency	Service	Region
1090 MHz	ADS-B (Mode S)	Worldwide
978 MHz	UAT (ADS-B)	United States only

Note: 978 MHz UAT is only used in the US below 18,000 feet. International flights and high-altitude traffic use 1090 MHz exclusively.