Enhancement and Metrological Characterization of an Accurate and Low-Cost Method based on Seismic Wave Propagation for Soil Moisture Evaluation

Monitoring soil moisture is a major interest for several practical applications. This task can be suitably performed through various methods; however, at the state of the art, there is not a single method that successfully combines ease of use, low cost, customization, possibility of measuring large volumes, and, most importantly, measurement accuracy. In this regard, seismic wave propagation (SWP)-based methods, which rely on the evaluation of the propagation velocity of a seismic wave vc through the soil sample under investigation, hold considerable potential for practical implementation. On such bases, in this work, first the authors propose an enhanced version of a previously developed SWP-based system for soil moisture measurement. Successively, to provide an exhaustive performance characterization of the system, a specific comparative methodology, based on reference timedomain reflectometry (TDR)-based measurements, is addressed. More specifically, SWP- and TDR-based measurements are simultaneously performed on river sand for increasing levels of water content. The TDR-measured moisture levels are taken as reference values and are used to infer the theoretical propagation velocity values vc,REF. Then, these reference values are suitably compared with those directly measured through the SWP-based system (vc,MEAS), thus allowing a consistent metrological assessment. The ultimate goal of this work is to validate and characterize the performance of the proposed SWP-based system in view of practical implementation for soil moisture evaluation.