Abstract: A method of determining the position of a target comprising the steps of: providing a transmitter or a plurality of transmitters to transmit a signal to the target, providing a receiver or a plurality of receivers to receive signals reflected from said target. Determining the time of arrival information of said reflected signal at the or each receiver; using information pertaining to the position of the or each receiver and/or the or each transmitter and with the information obtained determining the target position. Preferably the signal includes a modulated or coded portion unique to the transmitter; and said signal portion is associated with the or each particular transmitter by virtue of said signal portion. The signal maybe a mobile phone transmission, DAB, digital TV, digital Radio or digital satellite transmissions.

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