GNSS Code Multipath Short Time Fourier Transform Analysis

GNSS pseudorange multipath errors cannot be analyzed with the Fourier transform as they are non-stationary, thus other tools must be used. The objective of this paper is to investigate short-time Fourier transform (STFT) performance in detecting GPS code multipath and analyzing their frequency content. Multipath estimation was achieved by using the code-minus-carrier and the pseudorange multipath observable. Two real datasets were analyzed. A first experiment was carried out using data provided by Jiufeng (China) IGS station. Theoretical multipath time-frequency signature was identified by analyzing time-series provided by a simulator under the same conditions of the analyzed station. The spectrograms calculated on the real data and those calculated on the simulated one show the same pattern, assessing the effectiveness of the STFT performance. Based on these results the STFT analysis was applied to a second dataset collected in a strong multipath scenario in Naples (Italy) allowing to identify the multipath sources