Fig. 3. Relationship of volumetric water content to determined dielectric constant derived with the empirical Topp equation (black dashed line), the complex refractive index method (CRIM) equation assuming a dielectric constant of 81 for water (black line), and derived by the CRIM equation using dielectric constants of water at 14°C (gray solid line) and 24°C (gray dashed line) for a frequency of 750 MHz.