By Nicolas ROUSSEL, Frédéric FRAPPART, Guillaume RAMILLIEN, José DARROZES, Frédéric BAUP, CuongHA 

In partnership with the CESBIO (Centre d’Etudes Spatiales de la BIOsphère) laboratory, an experiment of detection of the soil moisture variations through GNSS reflectometry (GNSS-R) has been conducted on an agricultural plot in Lamasquère (Midi-Pyrénées, FRANCE) from 5 February to 15March 2014 . The soil were bare and smooth during the experiment. The test site is equipped with a set of sensors (rainfall , temperature, soil moisture) to validate the local fluctuation of soil moisture content.

The technical implementation is based on the analysis of GNSS signals emitted in L1-band (L1GPS: 1575.42 MHz). The signals are decomposed into two components: the direct and the reflected signal (see Figure.).

The signal-to-noise ratio (SNR) measured by the antenna thus includes both a signal coming directly from the atmosphere and a signal which has interacted with the ground. The analysis aims to estimate the SNR information on the nature of the reflecting surface at the time of measurement, including the moisture condition.

Please check more details on data processing and results and outlook.

Decomposition of the incoming GNSS signal


This project has received funding from the European GNSS Agency under the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 641606.