RADAR is the device most commonly used to locate airplanes in flight. In the event of a crash, the aircraft is equipped with an ELT (emergency location transmitter) which broadcasts a radio signal to aid in the search for the aircraft. Emergency search teams can then use specialized radio receivers to locate the ELT, and thus the crash site.
transponder/radar
radar
radar
radar
Compass is a scientific instrument used to locate directions,specifically north.
Radar
A gamma radiometer or a gamma spectrometer.
Radar
radar
A compass is a scientific instrument used to locate the north magnetic pole. The magnetic changes in the Earth's core make the north magnetic pole move over time.
Radar.
An Astrolabe.