FLARM

Why Feed FLARM Data?

Just like feeding ADS-B, sharing FLARM data with OpenSky supports open aviation research and the public good. FLARM adds coverage of gliders, helicopters and other light aircraft that may not broadcast ADS-B, helping researchers understand traffic closer to the ground. Your receiver contributes to a shared historical dataset for studying low-altitude airspace use, collision risk, GNSS signal quality and soaring conditions.

Our paper OpenSky Report 2023: Low Altitude Traffic Awareness for Light Aircraft with FLARM explains the dataset and its research applications. See our Social Impact page for examples of how OpenSky data supports science and civil society.

OpenSky Network supports FLARM data collection in addition to ADS-B and Mode-S for research purposes. To contribute your FLARM data, you need an OGN receiver. If you already have one set up, sharing your data is straightforward. If not, you will need to install and configure an OGN receiver before proceeding. Start with OGN's hardware and software guide and receiver configuration guide.

The OpenSky feed sends raw demodulated messages to our FLARM collector. All messages received through this feed are stored in our Trino database for research. The feed is separate from OGN's APRS feed, so you can keep contributing to OGN while also sharing with OpenSky.

Step 1: Configure Your OGN Receiver to Feed FLARM Data

Edit the receiver configuration file used by ogn-rf and ogn-decode. Its name and location depend on your installation; the table below covers common Raspberry Pi setups. These locations follow the linked projects' published scripts and documentation. For a different version or a custom installation, check the configuration path shown on your receiver's local status page or in its service definition.

On installations using the traditional OGN service wrapper, /etc/rtlsdr-ogn.conf lists the programs and their receiver configuration files; put MergeServer in the receiver configuration, not in that service list. The named images and installers are community projects; check their supported Raspberry Pi and operating-system versions before choosing one for a new installation.

Add or update MergeServer inside the existing Demodulator section of the receiver configuration, or add the section if it is absent:

Demodulator:
{
    MergeServer = "flarm-collector.opensky-network.org:20002";
};

Keep your other receiver settings and any existing Demodulator options. Leave your OGN APRS settings in place to continue feeding OGN. The OpenSky feed requires outbound UDP traffic to flarm-collector.opensky-network.org on port 20002.

Some images, installers and containers generate the receiver configuration automatically. In that case, follow your installation's documentation to update its persistent settings or configuration template, so the MergeServer setting survives a restart. Check the generated receiver configuration to confirm the setting above is present.

Save the file and restart your receiver service to apply the changes. On installations with separate ogn-rf and ogn-decode services, restart ogn-decode after this change. Make sure the collector hostname resolves before the decoder starts; if its log reports a name-resolution failure, restore DNS and restart the decoder.

Step 2: Verify Data Sharing

Check that both ogn-rf and ogn-decode are running, and check the decoder's logs or local status page for errors. While aircraft are being received, you can check outbound traffic on the receiver with:

sudo tcpdump -ni any 'udp dst port 20002'

Packets sent to the collector confirm that your receiver is transmitting the feed. A quiet receiver may send no packets until it receives aircraft messages. Aircraft appearing on a live map alone does not confirm that your station is feeding OpenSky.

Currently, OpenSky does not provide detailed statistics about individual FLARM sensors or feeds. However, if you have any questions or run into issues, feel free to reach out to the OpenSky team for assistance.