Abstract: A sensor panel including a transmit coil for producing a magnetic field in response to a source signal, a plurality of receive elements, each responsive to changes in the magnetic field incident thereon to provide an output, and a cancellation circuit arranged to remove from the outputs any signal induced in each receive element by the transmit coil. The receive elements are arranged in a matrix to provide an indication of the shape of a detected object. The sensor panel can be incorporated as part of a detection apparatus for use in airports and the like, and can also be used to detect buried landmines and ordinances.