A device for detection of undesired objects on surfaces, for example airport runways co-ordinates sensed data from a plurality of sensor units. With radar sensors, synthetic aperture radar processing is found to be advantageous. A vehicle which is configured with a plurality of sensors may be either remotely controlled or autonomous. It may also be provided with communication equipment and debris retrieval apparatus and that includes both mobile sensing devices and fixed installations. A suitable mobile sensing device and a method for operating the debris detection system are also provided.