*Editorial* **Special Issue "Remote Sensing in Applied Geophysics"**

#### **Chiara Colombero 1,\*, Cesare Comina 2 and Alberto Godio 1**


Received: 9 October 2020; Accepted: 12 October 2020; Published: 18 October 2020

The Special Issue "Remote Sensing in Applied Geophysics" is focused on recent and upcoming advances in the combined application of remote sensing and applied geophysics techniques, sharing the advantages of being non-invasive research methods, suitable for surface and near-surface high-resolution investigations of even wide and remote areas.

Applied geophysics analyzes the distribution of physical properties in the subsurface for a wide range of geological, engineering and environmental applications at di fferent scales. Geophysical surveys are usually carried out deploying or moving the appropriate instrumentation directly on the ground surface. However, recent technological advances have brought to the development of innovative acquisition systems more typical of the remote sensing community (e.g., airborne surveys and unmanned aerial vehicle systems). At the same time, while applied geophysics mainly focuses on the subsurface, typical remote sensing techniques have the ability to accurately image the Earth's surface with high-resolution investigations carried out by means of terrestrial, airborne, or satellite-based platforms. The integration of surface and subsurface information is often crucial for several purposes, including the georeferencing and processing of geophysical data, the characterization and time-lapse monitoring of surface and near-surface targets, and the reconstruction of highly detailed and comprehensive 3D models of the investigated areas.

Contributions to the issue showing the added value of surface reconstruction and/or monitoring in the processing and interpretation of geophysical data, integration and cross-comparison of geophysical and remote sensing techniques were required to the research community. Contributions discussing the results of pioneering geophysical acquisitions by means of innovative remote systems were also addressed as interesting topics.

The Special Issue received grea<sup>t</sup> attention in the combined community of applied geophysicists and remote sensing researchers. A total of 15 papers are included in the Special Issue, covering a wide range of applications. This is one of the highest number of papers among the *Remote Sensing* Special Issues, showing grea<sup>t</sup> interest in the proposed topic. The relevant number of contributions also highlights the relevance and increasing need for integration between remote sensing and ground-based geophysical exploration or monitoring methods.

In particular, one of the main fields of research showing the potential integration of the geophysical and remote sensing techniques is archaeological exploration. Indeed, archaeologists often use near-surface geophysics or remote sensing in their research. However, these surface and near-surface data are rarely integrated to o ffer a robust understanding of the complex historical setting characterizing archaeological sites. Several research e fforts need therefore to be addressed to reach a more e fficient integration of the techniques in the archaeological field. In this Special Issue, research e fforts are particularly related to: integrating aerial and terrestrial remote sensing programs to identify di fferent uses of archaeological sites through time and across space [1]; building high-resolution maps of electrical resistivity using computer-assisted and remote sensed acquisition tools [2]; multidisciplinary integration of remote sensing and archaeological data with electric resistivity tomography and frequency domain electromagnetic measurements to provide new useful and interesting information for archaeologists [3].

Several research e fforts were also devoted to the development of innovative acquisition systems integrating remote sensing and geophysical techniques with a precise georeferencing of the acquired data. These contributions are related to: the development of innovative low-cost autonomous vehicles for geological/geophysical studies of shallow water environments [4]; e fficient acquisition of frequency domain electromagnetic data with a specifically designed georeferenced wooden carriage to allow for integration with other remote sensing data [5]; automated resistivity profiling with constant GPS referencing and combined Digital Terrain Model to obtain correct data positioning and topographic reconstruction [2].

The integration of remote sensing and applied geophysics techniques has also been applied in environmental and geomorphological conditions of test sites requiring special attention. This can be the case of wide research areas, where the integration of localized geophysical data and wide remote sensing imagery is essential for a more accurate reconstruction of the environment, particularly in the hydrogeological framework [6,7], or in remote areas where acquisition and interpretation of geophysical measurements is challenging and feasible only with the help of remote sensing approaches. This is particularly true for the cryosphere, e.g., inland glaciers [8] and Antarctic ice sheet [9], or for the exploration of other planets and satellites [10]. In this last context, remote sensing techniques clearly play a major role in the e ffective acquisition of geophysical data.

The abovementioned applications appear to be the research fields where an e ffort in the integration of remote sensing and geophysical methodologies can be more successful, resulting in an increased comprehension of the investigated sites and in the improved e fficiency of the combined surveys. Other papers in the Special Issue could nevertheless sugges<sup>t</sup> additional interesting development topics; this is the case for papers focusing on the combination of geodetic and seismological observations for an increased understanding of local subsidence events [11] or wider scale post-seismic deformations [12].

As a conclusion, we can foresee a growing interest in the collaboration between the research communities of remote sensing and applied geophysics, with many potential overlapping research topics and undeniable benefits in the integration of di fferent research approaches. Particularly, remote sensing data and data acquisition approaches are still of grea<sup>t</sup> interest and support for applied geophysics researchers since they can further help in the correct georeferencing of the acquired geophysical data and in a better comprehension of the test site settings, which could significantly improve the interpretation of geophysical evidence.

**Author Contributions:** The authors contributed equally to all aspects of this Editorial. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** We would like to sincerely thank all the authors who contributed to this volume and all the reviewers for their valuable and constructive work. We are grateful to *Remote Sensing* Editorial Sta ff for providing us this opportunity and constant support. We especially thank Traey Wu for the substantial work and essential help in all the processes of this Special Issue.

**Conflicts of Interest:** The authors declare no conflict of interest.
