Energy Coupling
Energy coupling with the ground can be variable, depending on the type of surface materials present. In this profile, collected along a street in southern Portugal, limestone cobbles had poor coupling properties, and energy propagated to only about 40-50 nanoseconds. When the antennas crossed onto asphalt (A) coupling improved dramatically. Reflections that are visible at 60 and 90 nanoseconds on the right side of the reflection profile are barely visible (B) under the limestone cobble pavement.
Radar energy coupling variations are also important because these changes can be confused with variations in reflectivity of materials in the ground when viewed in profiles. When antennas move over un-even ground and clumps of vegetation (A), antenna coupling changes the nature of waves traveling through the ground, producing anomalous amplitude changes (B), which can be misinterpreted as geological or archaeological changes.
