How can velocity be extracted from hyperbolas?
Accurately determining the depth of a reflection in a GPR data record requires knowledge of how fast the signals travel in the material under investigation. Several techniques are used such as CMP (common mid-point), WARR (wide angle reflection and refraction), known-depth-target, hyperbolic fitting to a local target and diffraction tail matching. All of these techniques require GPR measurements along a traverse where the geometry is varying in controlled fashion. In other words, the distance to a target varies such that estimates of velocity can be extracted. Figure 1: The GPR traverse should be perpendicular to the pipe or cable strike direction. For pipe and cable location, or, in the Conquest example of rebar and conduit location, long linear features are localized targets if the GPR system traverses perpendicular to the feature alignment (Figure 1). To estimate velocity, the path length to the object must vary. Figure 2: Plan view looking down on ground from above. Traverse 1 is p
