What Controls Penetration?
Radio waves do not penetrate far through soils, rocks and most man-made materials such as concrete. The loss of radio reception or cell phone connection while driving a car through a tunnel or into an underground parking garage attests to this. The fact that GPR works at all depends upon very sensitive measuring systems being used and specialized circumstances. Radio waves decrease exponentially and soon become undetectable in energy absorbing materials, depicted in Figure 1. Figure 1: GPR signals decay exponentially in soil and rock. The exponential attenuation coefficient, a, is primarily determined by the ability of the material to conduct electrical currents. In simple uniform materials this is usually the dominant factor; thus a measurement of electrical conductivity (or resistivity) determines attenuation. In most materials energy is also lost to scattering from material variability and to water being present. Water has two effects; first, water contains ions which contribute to
