There are 3 ways that relative dielectric permittivity (RDP) affects Ground Penetrating Radar waves. 1) wave velocity. RDP and wave velocity have an inverse relationship. So, if the material has a high RDP, then the waves will move slowly. 2) wavelength. GPR antenna of a given frequency will actually produce waves with different wavelengths depending on the RDP of the material. Waves produced by the same antenna will have shorter wavelengths when propagating through soils with higher RDP (example: saturated silts) compared to lower RDP (example: dry sand. 3) footprint. Soils will lower RDP values will construct the spreading of a GPR wave. So, waves produced by the same antenna will spread out more at a given depth in dry sand and spread out less at that same depth in saturated silts.