Investigation of the GPR reflection pattern for shallow depths on a test site

Different materials such as loess, metabasalt and shales with a varying degree of weathering as well as an artificial reflector were studied on a test site at the University of Giessen using ground penetrating radar (GPR). The test site contains structures of different geometry within a depth range of one meter. All materials originate from the Lahn-Dill-Bergland (south-eastern part of the Rhenish Massif in Germany). The test-site is equipped with several time domain reflectometry (TDR) probes to monitor soil water content changes. Systematic investigations of the reflection patterns were performed with 100, 200,400,500 and 900 MHz antennas with respect to the antenna orientation, dielectric coefficient, attenuation, soil water content and the corresponding reflection coefficients of different materials. The antenna orientation creates no significant influence, whereas the influence of water content changes was high. The use of different antennas proved that the 400 MHz antenna is most suitable for this shallow depth test site. Furthermore, the GPR affecting properties of the region-specific materials could be outlined under almost natural conditions on the test site. The results help to increase the quality of GPR surveys in periglacial slope deposits.