ABSTRACT
Data analysis is the process of extracting useful information from observed or measured signals and phenomena. Signals are interpreted here in the mathematical sense of functions that depend on one or more independent variables in a given domain. It is a truism, if not a tautology, that spatial data collected for analysis create their first impact on the analyst in the domain in which they are observed - the space domain. A wave belonging to a signal in the time domain has a duration in time called its period, or wavelength, where "length" refers to a time interval. It is worthwhile to reinforce the concepts of frequency and wavelength with a specific geophysical example before delving from a more theoretical viewpoint into the mathematics of spectral analysis. Static signals on the spatial domain usually do not exhibit predominant periods, or resonances, with respect to the spatial coordinates, but their analysis in the corresponding spectral domain is nonetheless informative.
