An Alternative Approach for Estimating SNR Metrics in GPS-IR

摘要

GPS interferometric reflectometry (GPS-IR) is a bistatic radar remote sensing technique that has the potential to retrieve environmental variables such as soil moisture, snow depth and vegetation parameters. The direct and reflected signals will be mixed by omni-directional geodetic GPS antenna and the interfer?ence patterns of the both signals are recorded in signal-to-noise ratio (SNR) data. The SNR metrics, which refer to the phase, amplitude and reflector height, are the key parameters in subsequent analysis and applications of GPS-IR. Lomb-Scargle periodogram (LSP) is commonly used to estimate the dominant frequency of the detrended SNR interferograms, and the dominant frequency is converted to an effective reflector height, while phase and amplitude are finally estimated with least-squares method. In this study, the SNR metrics are determined with an alternative approach which on the basis of the least squares spectral analysis (LSSA). The core of the procedure is detecting the underlying periodicity terms in the detrended SNR interferograms, and then confirming the statistically significant spectral peaks according to the criteria formulated with Fisher distribution. The performance of the approach is examined with eight satellite tracks at the P041 site, the residuals show a 0-38% reduction in the root mean square (RMS) value compared to the LSP method and better distribution.