If you’re already using a software defined radio to monitor the RF spectrum, you can put it to use monitoring local air traffic to enhance your situational awareness in an emergency.
Why Monitor Air Traffic?
While monitoring RF traffic (such as ham radio transmissions, P25 communications and other signals) can provide critical information during emergencies, they don’t give us the full picture of what is going on around us.
Monitoring air traffic provides real-time insights into the movement and behavior of aircraft in your area. It enhances situational awareness, helps identify unusual activity, and supports communication during emergencies. By tracking flight paths and accessing broadcasts like weather and NOTAMs, you can make informed decisions and stay connected to evolving airspace conditions.
- Tracking Aircraft Movements – During emergencies, knowing the position of aircraft, including rescue planes, helicopters, or drones, can help coordinate response and avoid conflicts.
- Understanding Airspace Usage – Monitoring can reveal changes in normal air traffic patterns, such as reroutes or restricted airspace. This could help indicate the severity, nature, and scope of an emergency.
- Receiving Emergency Broadcasts – UAT equipped aircraft often broadcast weather, NOTAMs (Notices on Air Missions), and emergency information that can be critical for real-time decision making.
- Spotting Unusual Activity – Unexpected aircraft or activity in your area may signal evacuations, supply drops, or other emergency operations after a disaster.
- Supporting Communications – ADS-B and UAT data can compliment other communications by providing additional context, like estimated arrival times for air resources.
ADS-B vs UAT
ADS-B (Automatic Dependent Surveillance–Broadcast) and UAT (Universal Access Transceiver) are both communication protocols used in aviation to enhance situational awareness and air traffic management. They allow aircraft to broadcast their position, speed, and other flight data to ground stations and nearby aircraft.
ADS-B is a global standard, primarily used on the 1090 MHz frequency, while UAT, exclusive to the U.S., operates on 978 MHz and adds capabilities like weather and traffic updates for general aviation.
Automatic Dependent Surveillance - Broadcast
ADS-B is a widely adopted standard for aircraft transponders across the globe and is a great starting point for monitoring air traffic.
- 1090MHz
- Wide Global Adoption
- Position, Altitude, Speed, Aircraft Identification
- Mandatory for Most Aircraft
Universal Access Transceiver
UAT is exclusively used in the United States for general aviation below 18,000ft, but can be another good option to monitor if you live in the US.
- 978MHz
- US Specific
- Includes weather traffic and NOTAMs (Notices to Air Missions)
- Optionally Used Mainly by Smaller Aircraft
To ensure that we have the most complete picture of the airspace during an emergency, we will be monitoring both ADS-B and UAT.
SDR Applications for Airspace Monitoring
When it comes to airspace monitoring, there are a wide variety of tools available, ranging from mobile apps and online platforms like FlightRadar24 and ADS-B Exchange to more advanced SDR-based software such as Dump1090, Dump978, and PyAware. These tools allow users to gather and analyze air traffic data, whether they’re accessing publicly available information through online platforms or capturing real-time signals with software-defined radios for a more direct, ad hoc approach.
Each tool comes with its own set of advantages and limitations, offering users different ways to monitor and interpret the airspace around them.
Dump1090
Dump1090 is an open source application used for decoding ADS-B signals transmitted by aircraft on the 1090MHz frequency. It allows you to track real-time aircraft data including position, altitude, speed, and identification directly from an SDR receiver.
It is lightweight, easy to set up, and provides a web-based interface for visualizing air traffic.
Dump978
Dump978 is a tool for decoding UAT signals transmitted on the 978 MHz frequency, which is primarily used by general aviation aircraft in the United States. While Dump1090 focuses on ADS-B data from commercial and larger aircraft, Dump978 provides access to weather, traffic updates, and other information tailored for low-altitude and small aircraft.
This makes Dump978 particularly valuable in emergencies involving general aviation, where weather and localized flight data can be crucial for situational awareness. By pairing it with Dump1090, you can monitor a more complete picture of airspace activity across multiple aviation tiers.
PyAware
PyAware is a powerful tool that integrates and enhances air traffic monitoring by combining data from both Dump1090 and Dump978 onto a single, unified map. This feature allows you to simultaneously track ADS-B and UAT signals, providing a comprehensive view of airspace activity.
For emergency applications, PyAware is invaluable as it merges commercial and general aviation data, enabling real-time monitoring of all aircraft in the area. With its user-friendly interface and map overlays, it simplifies situational awareness, making it easier to track rescue efforts, airspace restrictions, or supply drops in one place.
Online Tools and Mobile Apps
Many web-based tools and mobile apps aggregate air traffic data from various sources, allowing users to monitor aircraft movements without the need for an SDR. These tools often rely on publicly shared ADS-B and UAT data from other individuals and ground stations, which is then displayed in user-friendly interfaces.
Examples of these apps and websites include FlightRadar24 and ADS-B Exchange. FlightRadar24 collects data from both ground stations and aircraft transponders, offering a detailed, real-time map of air traffic. While it’s an excellent option for casual monitoring, it relies on aggregated, public data, which may not be as up-to-date or comprehensive as direct SDR feeds. Similarly, ADS-B Exchange is an open platform that shares live air traffic information, often relying on contributions from ADS-B enthusiasts with receivers, but with some limitations in terms of data granularity compared to direct SDR tracking.
While these tools are useful for general tracking, they don’t offer the same level of raw data and customization that SDR-based monitoring provides. With an SDR, you can access unfiltered data, allowing for more advanced analysis and control over the information you receive. For serious airspace monitoring or emergency use, setting up your own SDR-based system is the better choice, as it gives you the flexibility and accuracy needed for real-time, critical decision-making.
Types of Data
When getting started monitoring air traffic, one can quickly become lost in the lingo. While not a complete guide, below is an overview of some of the common terminology you may encounter.
ICAO Address
A unique 24 bit identifier assigned to each aircraft.
Squawk Code
A 4 digit code transmitted to identify its status or intentions.
Altitude
How high an aircraft is flying (in feet).
Ground Speed
Speed relative to the ground (in knots).
Heading
The direction the aircraft is pointed (in degrees).
Call Sign
The alphanumeric identifier of the flight.
Position
GPS location (longitude and latitude).
Vertical Rate
The rate of climb (+) or descent (-).
Track or Course
The actual path over the ground.
Limitations
As with any data collection methods, its important to understand the limitations of UAT and ADS-B data. Understanding the below limitations will allow us to adapt our approach and overcome these challenges,
Range is Line of Sight
While Aircraft signals are inherently easier to receive due to their altitude, they are still limited to line of sight propagation. At cruising altitudes of 30,000+ feet, signals can be received from hundreds of miles away – far exceeding UHF / VHF amateur radio repeaters. However they still aren’t immune to obstacles.
- Terrain and Buildings – If you’re in a valley or surrounded by tall buildings, those obstacles could block signals from lower flying aircraft, especially during takeoff and landing.
- Weather Conditions – Heavy rain, snow, or thunderstorms can reduce signal reception quality, greatly reducing your detection range.
Limited Context
The basic information you get from UAT and ADS-B (such as altitude, speed, heading, and squawk codes) tells you a lot about what an aircraft is doing, but not why. For example, an aircraft circling could indicate holding for weather or an air emergency, but you wouldn’t know which without more contextual data.
Information that could add context may include:
- Weather – Aircraft movements are often influenced by storms, turbulence, wind shifts, and other weather patterns. Integrating real-time weather overlays can give you a lot of context into air traffic patterns.
- Airspace Restrictions – Another piece of context comes from temporary flight restrictions and controlled airspace details. An aircraft avoiding a no-fly zone might seem to be taking a strange route unless you are overlaying airspace maps with your UAT / ADS-B feeds.
- Flight Purpose – Unless you have access to detailed flight plans or databases like FlightAware, you’re missing information about what a flight is for (commercial, cargo, private or military). A high speed descent may look unusual unless you know it is a military training exercise.
Overwhelming or Lacking Data
In high traffic areas (such as near an air field), the sheer volume of aircraft can make it harder to sift through the data for actionable intelligence and distinguish patterns. An over-saturated map can also make it harder to discern individual aircraft and spot patterns.
On the other hand, in more remote areas the lack of data can make it harder to detect patterns as well, or aircraft of interest may simply be out of range. With less planes on your map, anomalies may go unnoticed if there is too little data to derive patterns from.
Conclusion
Monitoring air traffic using tools like ADS-B, UAT, and various SDR applications can be a valuable asset in emergency situations. These systems allow for a clearer understanding of the airspace around us, helping to track aircraft movements, support communications, and identify potential threats or irregularities. However, as with any data source, there are limitations that must be taken into account, such as line-of-sight restrictions and the potential for overwhelming or insufficient data.
By combining air traffic monitoring with other forms of data collection and analysis, we can create a more comprehensive picture that supports better decision-making in critical situations. Ultimately, while these tools are powerful, they are most effective when used alongside other resources to ensure that all angles are covered in an emergency.