Planes are overhead frequently. It's easy to look-up at a passing contrail and wonder where it's going. Thanks to a radio transponder now present on most aircraft called Automatic dependent surveillance—broadcast, or ADS–B, it's possible to crunch data about the planes around us. Passenger flights, cargo, military or the small Cessna flying overhead: it's possible to find their flight paths and ownership records.
We'll talk about how hobbyists can get at ADS-B data and what they might do with it. We'll also consider, briefly, how accident investigators can use ADS-B data to fill-in details of what happened when a plane crashes.