Evaluation of the benefits for mapping faint archaeological features by using an ultra-dense ground-penetrating-radar antenna array

Modern archaeo-geophysical radar surveys are often executed with multichannel antenna arrays, which allows a much faster survey progress combined with a denser profile spacing. Furthermore, from a methodological point of view, a full 3D dataset is necessary to resolve small targets of a few decimetre diameter. However, only a few test surveys deal with the evaluation of the real improvement in data quality by applying such multichannel arrays. In this paper, a test survey with the IDS Stream-C 600-MHz radar device on a small area covering the Roman Bath of Kempten-Cambodunum is presented. The aim of the study is to figure out whether faint archaeological remains like hypocaust pillars, that is, the pillars of a Roman floor heating system, that are missed by single-channel devices, are detectable in an ultra-dense antenna array. Thus, the same area was simultaneously mapped with both GPR configurations. The results of this case study demonstrate the benefit of such antenna arrays for the archaeological prospection of small subsurface features with a diameter of 25 cm or less. For ground-truthing of the results, a comparison with old excavation maps was executed.