Impact of Soil Properties On Ground Penetrating Radar Responses.

Landmines are extremely lethal and hazardous weapons of war. Approximately ten million land mines are scattered throughout the world. The detection, removal and destruction of these landmines is very difficult, as there are environmental, mechanical and economic aspects which make their removal and destruction more complicated. One such aspect is the influence of various soil parameters which can cause a decline in the efficiency of mine detectors using ground penetrating radar (GPR). GPR, combined with a metal detector, is used to detect land mines having a low metal content, and has also been exploited to diagnose soil properties. In various previous studies, GPR equipped mine detectors were found to give varied responses to simulated land mine targets when some certain soil environmental conditions existed. These variations in GPR alerts are found to be very specific to some specific soil physical and chemical properties; such as soil moisture, electrical conductivity (EC), salt content, clay content, bulk density and texture of soil. A field experiment with five different soils has been conducted to examine the effect of different soil properties on a GPR equipped mine detector. Soil selection was based on the NRCS GPR Suitability Soil Map (http://soils.usda.gov/survey/geography/maps/GPR/index.html ). Six soils were collected from different parts of Missouri and placed in plastic tubs (135cm X 96cm X 58cm) in five replicates. Digital soil sensors were placed at three different soil depths in each of the tubs to measure the variability of moisture, temperature and electrical conductivity with time. Mine targets (simulants) were placed in two replicates per soil types following split plot design. One tub of each soil type was kept target free and used to train the AN/PSS-14 mine detectors. The detector was first trained in the training tub and then swept over the targets placed in other tubs of same soil type to take the data. The training and sweeping processes were followed similarly for all of six soil types at the time of data collection. Data collection from the detector was followed once to thrice a day and 7-10 times a week based on weather variability. The soil environmental data collected by the soil sensors are digitally stored in dataloggers and downloaded twice a month. The initial findings suggest that the GPR responses were impacted most by soil texture, moisture and temperature. In some cases, when the soils were moist effects of salt content was also found to influence results. The overall results suggest that soil parameters have strong impacts on GPR responses which vary extremely with soil texture and can be considered as an important factor for decision making when conducting mine detection operations. The output of the study will help improve the knowledge of mine detector operators related to GPR functionality under certain soil properties and in turn will reduce the risks to operators and civilians through a reduction in misidentified targets.