1. A data storage medium encoding a machine-executable or digital processor-executable program, the program including a sequence of instructions for performing a method, the method comprising: receiving a plurality of temporal sequences of measurements of a selected local environmental condition, each sequence of measurements being made by a corresponding sensor node; determining an amount of correlation between the sequences of measurements of the selected local environmental condition received from two or more of the sensor nodes; and estimating a distance between the two or more of the sensor nodes based on the determined amount of correlation.