Geostatistical analysis of a ground penetrating radar reflection image can be used to quantify the maximum correlation direction and the range of horizontal and sub-horizontal radar reflections. A review of previous work, and an analysis of a photograph of layered sediments, suggest that the vertical resolution of a radar image strongly affects its lateral correlation structure. Numerical modeling was used to generate synthetic radar sections and investigate the effect of the vertical resolution of the radar measurement on the link between the correlation structure of the radar reflections and the true correlation structure of subsurface water content. The horizontal range of the radar reflections decreased as the vertical resolution improved, closely matching that of the water content when the vertical resolution was approximately equal to the vertical range of the water content.