Simulation and Correction of Double-Peak Errors in GPS L2P(Y) Signals for GNSS-IR Applications

GNSS Interferometry Reflectometry (GNSS-IR) technology achieves sensing of the surrounding environment using geodetic GNSS receivers. However, a distinctive type of GNSS-IR error manifests in the GPS L2P signal, characterized by a "double-peak" phenomenon in the signal-to-noise ratio (SNR) spectra, leading to inversion errors in GNSS-IR. Currently, the origins of this error are unclear, and corresponding correction strategies are lacking, thereby constraining the application of the GPS L2P signal. This study aims to delve into the causes of the double-peak error and propose a correction method. Firstly, according to the SNR forward model and the L2P tracking method, we simulated the L2P SNR arcs tracked through cross-correlation and Z-tracking methods. The simulated L2P SNR arcs exhibit oscillatory characteristics influenced by the L1 signal. Subsequently, various sites situated in marine, reservoir, or permafrost regions are chosen to analyze the spectral characteristics of L2P SNR data. The recorded L2P SNR sequences correspond well with the simulated L2P SNR sequences. We further scrutinize the impact of double-peak errors on L2P inversion results. Finally, we present a correction strategy for the "double-peak" error. The results indicate that the proposed error correction strategy effectively rectifies the L2P "double-peak" error, thereby enhancing the utility of GPS L2P signal inversion in GNSS-IR applications.