RAD-SEIS: Direct acces for ground-penetrating radar to reflection seismological techniques

Constant-offset georadar profiles look similar to stacked common mid-point seismic sections. Yet, technologies used for the field aquisition, processing and interpretation of seismic reflection data are significantly advanced with respect to what is common today in ground-penetrating radar. To take advantage of seismic techniques, the recently developed RAD-SEIS system allows: (a) direct digital recording in standard seismic SEGY data format; (b) continous profiling with accurate automatic antennae positioning; (c) programmable aquisition of constant-offset and multi-offset sections and cubes. The upgrade of the relatively inexpensive analog GSSI SIR-3 unit is achieved by adding a 16-bit digitizing board to a portable 486 personal computer and by employing a newly designed method for automatically triggering the system at constant spatial intervals as small as 1 centimeter. Programming of the 486 computer, using software tools provided with the digitizing board, allows the data to be recorded directly in SEGY format. In the multi-offset mode, an end-on "source-receiver" spread geometry, typical of that employed in reflection seismic surveying, is used. At the processing facility, the georadar field data are transferred from the personal computer via a network link directly into a workstation-based seismic processing and interpretation package. 300 Mbytes of field data, typical of a single day's multi-offset profiling, can be transferred in less than 60 minutes. Although turnaround time for processing large georadar datasets is relatively short, analog paper hardcopies, which are recorded directly in the field, remain an essential means for quality control and can help guide the surveying strategy.