My interest in tracking aircraft started long before my 35 year career as an RAF Air Traffic Controller. The ability to detect and display aircraft on a computer screen seemed impossible, especially as we were told that the radar head needed to be within a certain distance of the tower and that sending radar data by land-line was difficult if not impossible. As radar technology evolved and 'digital' data became the norm, the routine display of radar data from remote radar heads became the normal way of operating. However, this didn't help the aviation enthusiast who wanted to be able to see that data at home.
As the skies became busier and the requirement for additional navigational equipment on aircraft became more important, Automatic Dependant Surveillance - Broadcast (ADS-B) arrived on the scene. Operating in a different manner to the 'Mode-C' transponder that had to be interrogated by equipment on the ground and the transmission from the aircraft received and interpreted, ADS-B transmits data automatically without the need to be interrogated by a ground station. ADS-B transmissions follow an international standard and are not encrypted and can therefore be detected and interpreted by a suitable receiver and software.
Two domestic ADS-B receivers appeared on the scene, the Kinetic Radar SBS-1 and the AirNav Systems RadarBox. Both receivers detected the ADS-B transmission from aircraft and displayed them on a PC using Windows software. Aircraft could be detected routinely out to 200 miles from the receiver, depending on location and antenna. However, AirNav went one step further and gathered the data from all the RadarBox receivers (with user permission) and made this available to all other RadarBox users as a subscription service. This was a huge development, allowing users to see aircraft anywhere in the world where there was a RadarBox receiver. Both the RadarBox and the SBS-1 were reasonably expensive and the additional RadarBox subscription service added to that cost.
Kenetic Aviation SBS-1
If we jump forward a decade or two, availability of aircraft data via the Internet is common, with providers such as FlightRadar24, RadarBox24, Planefinder, and FlightAware all providing world-wide coverage of primarily civilian air traffic. Why only civilian traffic? The providers listed all have to satisfy the aircraft operators and these operators can choose not to have their aircraft displayed. So, not really a solution for those of us who have an interest in military aviation.
Enter stage left the incredible and very affordable Raspberry Pi computer and some very clever amateur experimenters. It was discovered that the USB 'TV' receiver stick with an RTL chip could be used as a wide-band Software Defined Radio (SDR) receiver and it was quite capable of receiving the ADS-B transmissions from aircraft on 1090Mhz. More clever people wrote software to run on the Pi and to display it on a computer screen.
360Radar is a browser-based aircraft tracking system designed to track all ADSB-equipped aircraft within range of our receivers. For those that don't broadcast their locations our MLAT server calculates their position as long as the aircraft can be seen by three or more receivers.
With over 500 receivers stretching across most of England, Wales and Scotland as well as Ireland, there is good coverage down to a few hundred feet above the ground in many places.