Geoscience Reference
In-Depth Information
variability in water content. Numerical modeling of a two-layer soil water content profile demon-
strated that the measured water content could, depending on the thickness of the upper layer, be
overestimated for a wet layer over a dry layer and underestimated for a dry layer over a wet layer
(Redman et al., 2003). This case study will outline the surface reflectivity methodology, present
field data examples, and the results of numerical modeling on the effects of surface roughness on
GPR measured soil water content.
24.2 MethodoloGy
The GPR, consisting of a transmitter and receiver, is elevated above the surface at a typical height
of ~1 m as shown in Figure 24.1. A vehicle-mounted implementation of a surface reflectivity system
(Figure 24.2) shows the GPR mounted to the left of the vehicle, with GPS providing positioning
information. The transmitter emits a short EM pulse. Part of the energy is transmitted into the soil
and part is reflected back into the air. The reflected pulse amplitude is measured in the receiver.
GPR
Transmitter
Receiver
Reflected
pulse
Air
Soil
Transmitted
pulse
fIGURe 24.1
Ground-penetrating radar (GPR) configuration for surface reflectivity method.
fIGURe 24.2
Vehicle-mounted ground-penetrating radar (GPR) surface reflectivity system for acquiring
soil water content measurements. GPR (Noggin 500) is shown on the left side of the vehicle. GPS provides
positioning information.
