Agricultural drainage pipe detection using ground penetrating radar: Effects of antenna orientation relative to drainage pipe directional trend

Authors: Allred, Barry

Submitted to: Symposium on Application of Geophysics to Engineering and Environmental Problems Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/10/2011
Publication Date: 4/11/2011
Citation: Allred, B.J. 2011. Agricultural drainage pipe detection using ground penetrating radar: Effects of antenna orientation relative to drainage pipe directional trend [abstract]. Symposium on Application of Geophysics to Engineering and Environmental Problems Proceedings.

Interpretive Summary:

Technical Abstract: Locating buried agricultural drainage pipes is a difficult problem confronting farmers and land improvement contractors, especially in the Midwest U.S., where the removal of excess soil water using subsurface drainage systems is a common farm practice. Enhancing the efficiency of soil water removal on land already containing a subsurface drainage system typically involves installing new drain lines between the old ones. But before this approach can be attempted, the older drain lines have to be mapped. Previous research strongly supports the feasibility of using ground penetrating radar (GPR) to find buried agricultural drainage pipes. However, one aspect of GPR drainage pipe detection needing further investigation are the effects on the GPR pipe response associated with antenna orientation relative to drainage pipe directional trend. Therefore, a field research study was carried out at a specially designed test plot for the purpose of assessing GPR drainage pipe detection impacts based on antenna orientation relative to drainage pipe directional trend. Antenna orientations perpendicular and parallel to drain lines were tested using both 250 MHz and 500 MHz antennas. GPR data was collected under soil moisture conditions that ranged from dry to extremely wet (saturated) and with drainage pipes that were air-filled, water-filled, soil-filled, and/or a combination. Study results indicate that there can be substantial differences in the strength of the GPR drainage pipe response for an antenna orientation perpendicular to a drain line versus an antenna orientation parallel to a drain line. Whether an antenna orientation perpendicular to a drain line works better or worse for GPR drainage pipe detection than an antenna orientation parallel to a drain line was found to depend on factors that include antenna frequency, soil moisture conditions, material inside the drainage pipe (air, water, soil), and the GPR measurement transect orientation relative to drainage pipe directional trend. Consequently, the findings of this research imply that the antenna orientation relative to the GPR measurement transect direction is an important field survey consideration regarding GPR mapping of agricultural drainage pipe systems.