The accuracy of geomagnetic field measurement at a given point on the Earth's surface is limited by the ambient magnetic noise level which is usually determined by the superposition of signals generated from different sources. The noise that dominates in all physical systems, particularly in spectral regions at lowest frequencies is the flicker noise [Vladimirov and Kleimenova 1962]. The analysis of the background noise that exists on the site is essential to design a new magnetic Observatory. Noise measurements allow then to evaluate the magnetic pollution status of the area and constitute a basic cognitive tool for the building of a new magnetic Observatory. Only by comparing signals of natural origin and the noise is possible to characterize the site. The purpose of this note is the...