Description of the variance structure of soil properties by computation of a Fourier spectrum requires considerable attention to the procedure and methods necessary to fit requirements of the discrete Fourier transformation process. Two schemes for space sampling are compared and evaluated. Replacement of the traditional rectilinear transect by a circular transect is proposed and justified both from theoretical and experimental viewpoints. The spectrum is modelled in a log-log picture by a straight line whose equation parameters can be used to describe the variance structure. A Swiss dense grid digital elevation model of high relief is used to illustrate the concepts and computations.