Improvements Continue To Drive GPR Applications

By Jeff Griffin, Senior Editor | April 2009 Vol. 64 No. 4
Mala USA's GPR

Generally speaking, GPR systems perform much better in drier soils and sandy soils. But other factors also determine how effective a GPR system will perform including: size and diameter of the target, composition of the target, depth of burial of the target, and expectations and experience of the GPR operator. GPR systems perform less effectively in soils that are comprised of clay material, have high percentages of mineralization, or high moisture contents.

GPR locating systems offer several advantages, including the ability to detect metallic and nonmetallic targets, and generate a continuous data profile view along the survey path presented in real time during data collection. Also, target location can be determined very accurately, depth information can be readily determined provided that the GPR system is properly calibrated, and today's GPR systems have easy to use operator interfaces.

The reduced ability of a GPR system to detect buried targets in clayey or conductive soils is the primary system limitation. Other perceived limitations include higher costs compared to standard locators and that high quality GPR interpretation generally requires an experienced operator. In addition, most people introduced to GPR have been either oversold about a system's capabilities or have unrealistic expectations of what a GPR system can do.

Basic GPR technology is much the same as was used 10 to 15 years ago. However, improvements such as cart based GPR systems, user friendly software, and lower system costs have more readily placed the technology in the hands of technicians and engineers for use on everyday projects.

The next big advancements in GPR utility locating likely will be in the areas of stepped frequency or swept frequency radar systems. Unlike pulse systems which send out discrete signals centered around a particular frequency, stepped or swept frequency systems provide a broad range of distinct frequencies in order to maximize information returned from a buried target for size, depth, and composition. (Vermeer markets the Interragator EZ GPR single channel, pulsed radar system.)

Ditch Witch, Mike Dvorak, electronics account manager: A GPR locator works like any other radar – it sends out an electronic signal that bounces off "something" and returns to the home base. In the case of the GPR location equipment, the unit and signals are tuned for use in the soil. The information is presented to the operator on a lap top computer. The sign of a pipe or some other object underground is a "hyperbola" that shows up on the unit's screen.