1. A method comprising: sensing a local radio-frequency (RF) interference spectrum at each of a plurality of sensors positioned at a plurality of locations within a geographic region; and computing a non-parametric basis expansion model from the sensed RF interference spectrum, wherein the non-parametric basis expansion model comprises a set of reference basis functions that represent a frequency distribution of the RF power and a set of kernel-based interpolating functions that represent a physical distribution of the RF power throughout the geographic region, and wherein the kernel-based interpolating functions are computed in the non-parametric basis expansion model as coefficients to the reference basis functions and operate as bases weighting functions in the non-parametric basis expansion model; and constructing, in accordance with the non-parametric basis expansion model, a power spectral density (PSD) map representative of a distribution of RF power throughout the geographic region as a function of frequency and location.