GIRAS: an open-source MATLAB-based software for GNSS-IR analysis

Abstract

Global Navigation Satellite System Interferometric Reflectometry (GNSS-IR) has become a robust method to extract the characteristic environmental features of reflected surfaces, where the signal transmitted from satellites reflects before receiving at GNSS antenna. When the signal arrives at the GNSS antenna from more than one path, a multipath error occurs, which causes interference of the direct and reflected signals. The interference of direct and reflected signals shows a pattern for sensing environmental features, where the signal reflects, and multipath directly affects the signal strength. Analyzing the signal strength represented by the signal-to-noise ratio (SNR) enables the retrieval of environment-related features. The software developed, named GIRAS (GNSS-IR Analysis Software), can process multi-constellation GNSS signal data and estimate the SNR metrics, namely phase, amplitude, and frequency, for further computations with several optional statistical analyses for controlling the quality of the estimations, as required, such as snow depth retrieval, effective reflector height estimation, and soil moisture monitoring. The software developed in the MATLAB environment has a graphical user interface. To represent the processes of the working procedures of the software, we conducted a case study with 7-day site data from the multi-GNSS experiment (MGEX) Project network displaying how to process GNSS data with input and output file properties.