There are several problems that GPR practitions can encounter while conducting ground penetrating radar projects. These can include gradual transitions between materials, high attenuation rates, and the inability to estimate depth. One of the most dangerous is dealing with air waves. Why? Because air waves can produce false positives in your GPR data set!
Air waves are can produce responses in your GPR data that appear to be buried objects, but in reality they are signals from your gpr that reflected off of an object that is on the surface. For example, while collecting a line of data past a tree, the gpr wave can move across the ground surface, reflect off the tree, and be recorded by your receiving gpr antenna. The problem is that this reflection event appears in your gpr profile as if it occurred below the ground surface.
The first way to handle this issue is be aware of your surroundings. Recognize that the GPR antenna produces a pulse of energy that not only goes into the ground, but along the ground surface and even up in the air. Second, match the hyperbola to get a dielectric value or a velocity. A dielectric of 1 will indicate that the hyperbola was produced by an air wave.
Be alert, be cautious, and survey on!
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