Which statement about GPR behavior is supported by the provided material?

• A. GPR dissipation is not uniform with distance from the source
• B. GPR dissipation is uniform with distance
• C. GPR signals increase with distance
• D. GPR does not produce reflections

Answer: (A)

GPR energy does not fade uniformly as you move away from the source. The amount of dissipation depends on distance, the frequency content of the pulse, and the subsurface properties it encounters. As the wave travels, it spreads out (geometric spreading) and experiences material losses from the soil or rock it passes through. Different layers have different dielectric properties and conductivities, moisture levels, and salt content, which cause attenuation to vary with distance. Higher frequencies attenuate more quickly, so the pulse shape and amplitude change with range, adding to the non-uniform dissipation.

This aligns with the idea that dissipation is not uniform with distance from the source. The other statements don’t fit because GPR relies on reflections from impedance contrasts, so reflections are expected; energy typically decreases with distance due to attenuation rather than increasing; and uniform dissipation with distance would ignore the well-known effects of varying materials and frequency-dependent loss.