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1. What is AEROJAMMING?
AEROJAMMING is an application developed at the Faculty of Transportation Sciences, Czech Technical University in Prague, which automatically collects ADS-B data and, every 20 minutes, analyzes it to detect the presence and location of potential GNSS interference. The results are saved and displayed on the homepage, which by default shows the latest available 20-minute interval. Past data can be explored using the date and time picker.
2. What kind of interference does AEROJAMMING detect and how?
The algorithm used in the back-end of AEROJAMMING detects jamming (but not spoofing) by comparing theoretical and actual NACp (Navigation Accuracy Category - Position) values from ADS-B messages. This method is detailed in the Methodology for the Detection of Illegal Interference (starting on page 12). The algorithm evaluates whether the transmitted NACp values are plausible or if their decrease is too significant to be explained by normal conditions. If the decrease is implausible, it indicates interference.
3. Understanding the map with interference detection results
The map shows all ADS-B messages for which interference detection produced results. Some messages from the file may be omitted if they are corrupted or filtered out by the detection algorithm. More details can be found in the Methodology for the Detection of Illegal Interference. Besides the filters described in the methodology, AEROJAMMING applies additional filters to optimize performance and ensure that calculations are completed within a reasonable time after each 20-minute data interval is collected. One such optimization involves limiting the analysis to the Prague region, even though the ADS-B data – collected from receivers operated by FTS CTU in Prague – covers a broader area. The back-end calculation generates a CSV file with results, which you can download using the button (on small screens, press first).
Each plane on the map represents an ADS-B message: green indicates no interference, while red signals interference. You can click on any plane to view more information. When messages are too close together, they are clustered. This clustering behavior is explained in the map's legend at the bottom right corner of the screen.
In the top right corner, the Layer Control allows you to change source of the map tiles and enable or disable aircraft visibility. Each aircraft appears only once in the Layer Control, and disabling it hides all its messages.
Below the Layer Control, additional buttons offer quick options (from left to right):
- Select All Aircraft: Show all aircraft.
- Deselect All Aircraft: Hide all aircraft.
- Display Only Aircraft with Interference: Show only aircraft with one or more interfered messages.
4. Accessing the historical detection data
The homepage provides access to historical detections via the date and time picker in the bottom left corner (on small screens, press first). To view a past detection, select a date and time and press , or use the arrow buttons to navigate:
- Left Arrow: Show previous detection
- Right Arrow: Show next detection
- Double Right Arrow: Show latest detection
If a button is grayed out, the corresponding detection is unavailable.
Note on time change: Detection times are shown in Prague local time – either CET or CEST, depending on the time of year. During the transitions when the same hour occurs twice, a blue pop-up will appear above the date and time picker, allowing you to choose which instance of the hour you'd like to view data for.
Note on historical data availability: The system retains full detection data, including all 20-minute intervals and information about the messages present, for the past 500 days. After that, only information about the percentage of detected interference is preserved.
5. Accuracy of the detections
There are known inaccuracies and bugs in the interference detection module used by this application. This module is not developed as a direct part of AEROJAMMING. Future updates by the Faculty of Transportation Sciences may improve its accuracy. Known issues include insufficient data filtering – some of the filtering described in the Methodology has not yet been implemented in the module. As a result, you may sometimes see a single aircraft showing interference throughout its entire flight while others remain unaffected. This is a known issue.