1. A method of processing geophysical data, the method comprising determining an integral of a function of the geophysical data over an n-dimensional integration domain from the values of the function at a plurality of discrete data points within the integration domain, wherein the method comprises the steps of: (a) partitioning the integration domain into a plurality of k-dimensional simplexes, where k≦n; (b) integrating the function over each simplex; and (c) summing the results of step (b).