<title>Field studies of GPR air launched surface reflectivity measurements of soil water content</title>

The soil water content distribution at two field sites was measured with the air launched surface reflectivity method using a standard GPR system elevated ~1 m above the surface. Time domain reflectometry (TDR) measurements of water content were also acquired at these sites. At one site, water was applied to the surface in two separate experiments and the water content was measured during drainage. At the other site, a water content profile was acquired across two terrain types, a flat grass field and a corn field. Although the GPR surface reflectivity method was able to map the water content distribution at both sites there were substantial differences between these measurements and those acquired with TDR. The main contributors to these differences are likely scattering and changes in the nature of the gradational air/ground interface, related to spatial variability in water content.