A data processing method comprising: receiving, from each of a plurality of sensors each located at a respective location, a signal indicative of a respective value of a parameter measured by that sensor at a respective one of a plurality of successive times; and determining, based on the value of the parameter measured by one or more first sensors of the plurality of sensors at a respective one or more of the plurality of successive times, a value of the parameter at the location of a second sensor of the plurality of sensors at one of the one or more of the plurality of successive times.