Ground-based ground-penetrating radar (GPR) has been applied successfully for decades in archaeological geophysics. However, there are sometimes severe problems arising in cases of rough terrain, permission to enter a site, or due to vegetation. Other issues may also make it impossible to use conventional ground-based GPR. Therefore, mounting the GPR antenna below a drone could be a potential alternative. Successful applications of drone-based GPR have already been reported, e.g., in the fields of geological mapping, glaciology, and UXO-detection. However, it is not clear whether faint archaeological remains can also be mapped using this approach. In the survey discussed below, we tested such a drone-based GPR setup at an archaeological site in Bavaria, where well-preserved Roman foundations at a shallow depth are known from previous geophysical surveys with magnetics and ground-based GPR. The aim was to evaluate the possibilities and problems arising with this new approach through a comparison with the afore-mentioned data, obtained in previous ground-based surveys of this site. The results show that under certain circumstances, the archaeological remains can be resolved while using a drone. However, the remains are much harder to detect with a lower degree of resolution and survey setup and acquisition time play a crucial role for a successful survey. Especially relevant are two factors: First, the correct choice of profile orientation, as there are strong reflections caused by near-surface features (like field boundaries) due to decoupling the antenna from the ground. Second, a very dry soil is mandatory, as otherwise too much signal is lost at the air-ground-interface. Considering these factors, drone-based GPR represents a valuable tool for modern archaeological geophysics.

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.