GPR ground-wave parameters changes due to variation of soil moisture Henryk Marcak, Sylwia Tomecka-Suchoń, Rafał Czarny, Paweł Pysz, Akinniyi Akinsunmade and Tetiana Kril E3S Web Conf., 66 (2018) 01003 Published online: 26 November 2018 DOI: 10.1051/e3sconf/20186601003