filename : p_Leck01.pdf entry : article pages : 29-40 year : 2001 title : Investigating the True Resolution and Three-dimensional Capabilities of Ground-penetrating Radar Data in Archaeological Surveys: Measurements in a Sand Box. author : J. Leckebusch, R. Peikert booktitle : Archeol. Prospekt., vol. 8 editor : publisher : John Wiley & Sons, Ltd. language : english month : keywords : ground-penetrating radar; migration; resolution; accuracy; multiple; wavelength; antenna pattern; attenuation; modelling; isosurface; three-dimensional display abstract : The capabilities of ground-penetrating radar (GPR) were studied in a sand box under controlled conditions. To reduce the size of the necessary sand box, the structures were scaled by 50 per cent and the antenna frequency used was doubled from 500 MHz to 900 MHz. Blocks of concrete were buried to model Roman walls. Initial tests showed a great effect of the antenna orientation on the visibility of the structures, which is difficult to account for during a survey. The GPR profiles also showed a significant reduction of the signal amplitude by a strong reflector, obscuring any underlying object. After three-dimensional migration a single block was perfectly imaged. The signals from a second block, buried below the first, were obscured by several multiples, which prevent it exact detection. This was confirmed by numerical modelling. Comparing real data with modelling results showed that exploding reflector and plane wave models use an incorrect ray path. Only a so-called 1-to-1 adoption model gives comparable results. The measurements with two buried stones are in good agreement with the data from normal surveys. Tests have shown that the superposition of the reflection patterns from single stones makes the detection of any interior structure of a wall impossible. To visualize the three-dimensional information in the data set, a new technique was used: an isosurface of the reflection strength or amplitude envelope was calculated. This procedure makes the full three-dimensional information understandable and reduces the amount of data significantly. The isosurfaces can now be exported and combined with any other archaeological information in a geographical information system (GIS). The speed of this process makes it suitable for large surveys.