SOMETIMES the answer to a problem is all around you.
Air traffic controllers need to keep track of aircraft and other vehicles moving around airports, to prevent runway collisions. However, many smaller airports cannot afford ground radar, while at larger airports buildings can block radar signals.
To provide cheap, full coverage, physicist Haibin Gao at Saarland University in Saarbrücken, Germany, has developed sensors that can track vehicles by detecting the distortion they cause to the Earth’s magnetic field. “Everything is inside Earth’s magnetic field, so why not use it?” he says.
Large magnetic objects like the engines on aircraft…
