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Climate change is undoubtedly a big issue due to its devastating consequences. The enhanced resilience to natural hazards due to climate change belongs to the concept of smart cities. This Editorial proposes different uses of Geographic Information Systems to handle and disseminate data for natural disasters. Data are gathered from various data sources and are processed and visualized in maps using apps. These apps are available through the Internet or mobile devices and can be used to inform and train the stakeholders of disaster-prone areas in order to mitigate the impacts of disasters. © 2020 by the authors.

The aim of the current work is to introduce bathymetry data into Geographic Information Systems tools for mapping, monitoring and assessing the geohazards in the Greek islands between Crete and Kasos at the Mediterranean sea. The offshore area lying east of Crete is studied on the basis of new bathymetric data. The data was obtained by a multibeam sonar system which allows the imaging of the seafloor. The collected multibeam data have been extensively processed in order to be cleaned of erroneous beams, filtered of noise, processed of navigation data and interpolated of missing beams. The analysis and representation was performed with the ArcGIS software. Resulting maps were analyzed and presented. The analysis of the slope values and the watershed at the eastern part of Crete reflects intense tectonic activity. We have found out that the basin geometry is an elongated rectangular which is divided into seven sub-basins. The multibeam bathymetric data show that the relief is a complex compound of submarine canyons, landslides and a well-defined slump with vertical displacement. These conditions increase substantially the potential of a geohazard in the area. © Springer Nature Switzerland AG 2019.

Story maps are used as an interactive tool for communication and information dissemination. A web-based application using story mapping technology is presented to explore the Methana peninsula. This volcanic area is characterized by specific volcanic geoforms, unique flora and rich history. The story map combines maps, narrative texts and multimedia content. The spatial data produce thematic maps created by a Geographic Information System on geological data, historical monuments, biodiversity and hiking paths. The purpose is to highlight the distinguishing characteristics of the Methana peninsula, to enable users to interact with maps, texts and images and to inform professional and non-professional users about the particular aspects of volcanic areas. © 2018 by the authors.

The morphotectonic structure of the offshore area lying between Crete and Kasos is studied on the basis of new detailed bathymetric data. The resulting bathymetric map is presented. Qualitative analysis of morphological slope values, as well as the analysis of the watershed at the eastern part of Crete, confirms that the current seabed topographic relief reflects intense tectonic activity. The high morphological slope values indicate well-defined morphotectonic features, which mainly trend SW-NE and, secondarily, SSW-NNE. The main large-scale tectonic structures trend SW-NE correspond to the marginal faults that bound the Crete-Kasos basin. The overall basin geometry is an elongated rectangular which is divided into seven sub-basins, and the deepest one (2800m) is located at the eastern part of the area. Moreover, the complex regime of the seafloor includes submarine canyons, landslides and a well-defined slump with vertical displacement more than 400m.

In the present work, we test the application of boat-camera-based photogrammetry as a tool for Virtual Outcrops (VOs) building on geological mapping and data collection. We used a 20 MPX camera run by an operator who collected pictures almost continuously, keeping the camera parallel to the ground and opposite to the target during a boat survey. Our selected target was the northern part of Santorini's caldera wall, a structure of great geological interest. A total of 887 pictures were collected along a 5.5-km-long section along an almost vertical caldera outcrop. The survey was performed at a constant boat speed of about 4 m/s and a coastal approaching range of 35.8 to 296.5m. Using the Structure from Motion technique we: i) produced a successful and high-resolution 3D model of the studied area, ii) designed high-resolution VOs for two selected caldera sections, iii) investigated the regional geology, iv) collected qualitative and quantitative structural data along the vertical caldera cliff, and v) provided a new VO building approach in extreme logistic conditions.

This paper presents generic guidelines for constructing customised workflows exploiting game engine technologies aimed at allowing scientists to navigate and interact with their own virtual environments. We have deployed Unity which is a cross-platform game engine freely available for educational and research purposes. Our guidelines are applicable to both onshore and offshore areas (either separately or even merged together) reconstructed from a variety of input datasets such as digital terrains, bathymetric and structure from motion models, and starting from either freely available sources or ad-hoc produced datasets. The deployed datasets are characterised by a wide range of resolutions, ranging from a couple of hundreds of meters down to single centimetres. We outline realisations of workflows creating virtual scenes starting not only from digital elevation models, but also real 3D models as derived from structure from motion techniques e.g. in the form of OBJ or COLLADA. Our guidelines can be knowledge transferred to other scientific domains to support virtual reality exploration, e.g. 3D models in archaeology or digital elevation models in astroplanetary sciences.

Summarization: Story maps are widespread as an interactive tool used for science and spatial data communication, informationand dissemination. A Web-based application using story mapping technology is here presented to show the historical importance of Metaxa Mine, known also as Mavormatis mine. This mine is characterized by the presence of several key outcrops where the pumice layers of the Late Bronze Age (Minoan) eruption are very well exposed. We made up a tailored story map that combines maps, narrative texts, multimedia content and a brand-new 3D model. Its purpose is to highlight the visualisation and the exploitation of Metaxa Mine as a unique “geotope” of Santorini volcano, to enable users to interact with data and maps, texts and images, and to inform academic and non-academic audience about the historical and volcanological aspects of this geological site. The spatial and geological data of this story map involve thematic maps entirely created by a Geographic Information System. Παρουσιάστηκε στο: 5th International Conference on Geographical Information Systems Theory, Applications and Management

The contribution exposes and illustrates a general, flexible formalism, together with an associated iterative procedure, aimed at determining soft memberships of marked nodes in a weighted network. Gathering together spatial entities which are both spatially close and similar regarding their features is an issue relevant in image segmentation, spatial clustering, and data analysis in general. Unoriented weighted networks are specified by an ``exchange matrix", determining the probability to select a pair of neighbors. We present a family of membership-dependent free energies, whose local minimization specifies soft clusterings. The free energy additively combines a mutual information, as well as various energy terms, concave or convex in the memberships: within-group inertia, generalized cuts (extending weighted Ncut and modularity), and membership discontinuities (generalizing Dirichlet forms). The framework is closely related to discrete Markov models, random walks, label propagation and spatial autocorrelation (Moran's I), and can express the Mumford-Shah approach. Four small datasets illustrate the theory.

In the present work, we tested the use of selfie drones as a tool for 3D modeling, geological mapping, and data collection. The model we used is a 0.300-kg multirotor quadcopter being equipped with a 1/2.3-inch CMOS sensor capable of capturing 12 Megapixel pictures, attached to a 2-axis mechanical gimble and with approximately 16 minutes of flight time. Test sites are located in Santorini and are characterised by different settings: i) the 1570-1573 AD volcanic crater area, in Nea Kameni island, has a mostly horizontal topography; ii) the outcrop along Vlychada beach, showing layers of the Late Bronze Age (also well-known as Minoan) eruption, has mostly vertical topography. By applying the Structure from Motion techniques to pictures collected using the selfie drone, we were capable of: i) reconstructing the two sites with centimetric to subcentimetric resolution; ii) recognizing geological features on very high-resolution Digital Surface Models and Ortomosaics; iii) mapping vertical cliffs made up of volcanic deposits on 3D Digital Outcrops Models; iv) collect new quantitative data for both sites.