Discrete-Time Signal Processing
Discrete-Time Signal Processing
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Kriging is a widely applied data assimilation technique. The computational cost of a conventional Kriging analysis of N data points is dominated by the m iterations of the maximum likelihood estimate (MLE) optimization, resulting in a computational cost of O(mN^3). We propose two fast methods for estimating the hyperparameters in the frequency domain: frequency-domain maximum likelihood estimate (FMLE) and frequency-domain sample variogram (FSV), both of which reduce the cost of the optimization to O(N^2+mN) in the case of a regular Fourier transform (FT), and to O(NlnN+mN) in the case of a fast Fourier transform (FFT). In addition to this speed up, problems concerning positive definiteness of the gain matrix - which limit the robustness of the conventional approach - vanish in the proposed methods.