I Use the Kinetic Avionics SBS-1 Base Station Virtual Radar System to monitor aircraft flying around the Channel Island area.
Modern planes use something called an ADS-B (Automatic Dependent Surveillance-Broadcast) Mode-S transponder, which periodically broadcasts location and altitude information to air traffic controllers.
ADS-B is a system in which electronic equipment onboard an aircraft automatically broadcasts the precise location of the aircraft via a digital data link.
The data can be used by other aircraft and air traffic control to show the aircraft’s position and altitude on display screens without the need for radar.
The system involves an aircraft with ADS-B determining its position using GPS. A suitable transmitter then broadcasts that position at rapid intervals, along with identity, altitude, velocity and other data. Dedicated ADS-B grounds stations receive the broadcasts and relay the information to air traffic control for precise tracking of the aircraft.
Automatic – Requires no pilot input or external interrogation.
Dependant – Depends on accurate position and velocity data from the aircraft’s navigation system (eg. GPS).
Surveillance – Provides aircraft position, altitude, velocity, and other surveillance data to facilities that require the information.
Broadcast – Information is continually broadcast for monitoring by appropriately equipped ground stations or aircraft.
ADS-B data is broadcast every half-second on a 1090MHz, digital data link.
Broadcasts will most likely include some or all of the following information:
- Flight Identification (flight number callsign or call sign)
- ICAO 24-bit Aircraft Address (globally unique airframe code)
- Position (latitude/longitude)
- Position integrity/accuracy (GPS horizontal protection limit)
- Barometric and Geometric Altitudes
- Vertical Rate (rate of climb/descent)
- Track Angle and Ground Speed (velocity)
- Emergency indication (when emergency code selected)
- Special position identification (when IDENT selected)
The ability of a ground station to receive a signal depends on altitude, distance from the site and obstructing terrain. The maximum range of each ground station can exceed 300 nautical miles.
Using a receiver as shown above and a simple outside antenna it is easy to receive the ADSB information. when the receiver is linked to software it is possible to overlay this information on to a map to visually show the aircraft and direction of travel as can be seen from Virtual Radar which is all of the ADSB information as received by my ADSB receiving station.