A spatial preference query ranks objects based on the qualities of features in their spatial neighborhood. For example, consider a real estate agency office that holds a database with available flats for lease. A customer may want to rank the flats with respect to the appropriateness of their location, defined after aggregating the qualities of other features (e.g., restaurants, cafes, hospital, market, etc.) within a distance range from them. In this paper, we formally define spatial preference queries and propose appropriate indexing techniques and search algorithms for them. Our methods are experimentally evaluated for a wide range of problem settings.

Dynamic processes in coastal zones and human activities in the coastal environment produce pressure on cultural heritage, especially in touristic places. Unmanned aerial systems (UAS) are used as an additional tool for monitoring cultural heritage sites in sensitive coastal areas. UASs provide low-cost accurate spatial data and high-resolution imagery products in various spatial and temporal scales. The use of UAS for mapping cultural heritage sites in the coastal zone is of increasing interest among scientists and archaeologists in terms of monitoring, documentation, mapping, and restoration. This study outlines the integration of UAS data acquisition and structure from motion (SfM) pipeline for the visualization of selected cultural heritage areas (ancient harbors) in the coastal zone. The UAS-SfM methodology produces very detailed orthophoto maps for mapping and detecting cultural heritage sites. Additionally, a metadata cataloging system has been developed in order to facilitate online searching operations for all products of the data acquisition, SfM pipeline, and cartographic processes. For this reason, a specific metadata profile was implemented, based on the European INSPIRE framework. As a result, datasets reusability and catalogs interoperability are promoted.

This article focuses on the development of an educational outdoor adventure mobile app while presenting findings that were derived from various case studies that we conducted using it. The mobile application, called RouteQuizer, is complemented by a web application and a database, forming a system that enables teachers to create educational treasure hunt activities for their students and monitor their performance. The aim of the research was to create a system that would exploit all possible Outdoor Adventure Education (OAE) and treasure hunt benefits while excluding possible smartphone use negative consequences. The development of the system took place in Greece and began in December 2017, by conducting a nation-wide research examining Greek secondary teachers’ Information and Communication Technology (ICT) literacy and perceptions on smartphone use and outdoor activities. By June 2018, 700 questionnaires were collected. In order to test the system, in March 2018, we conducted a pilot case study in Lesvos island Greece and between July 2018 and February 2020, we conducted four additional case studies and a teacher training program, all of which took place in Lesvos island Greece. During the development process of the mobile application, we focused on the participatory aspect of the process, paying special attention to the teacher and student evaluation during the design and prototyping phases. Considering that the system is educational we research whether the mobile application provided effective learning outcomes and whether it benefited students’ social and physical skills. The results that we collected suggest that the mobile application is an effective learning tool while mobile learning and treasure hunt benefits have been repeatedly confirmed during the case studies. Greek teachers and students also proved to be capable smartphone and computer users, and reported being willing to participate in similar activities in the future.

The identification of oceanographic circulation related features is a valuable tool for environmental and fishery management authorities, commercial use and institutional research. Remote sensing techniques are suitable for detection, as in situ measurements are prohibitively costly, spatially sparse and infrequent. Still, these imagery applications require a certain level of technical and theoretical skill making them practically unreachable to the immediate beneficiaries. In this paper a new geospatial web service is proposed for providing daily data on mesoscale oceanic feature identification in the North Aegean Sea, produced by Sentinel-3 SLSTR Sea Surface Temperature (SST) imagery, to end users. The service encompasses an automated process for: raw data acquisition, interpolation, oceanic feature extraction and publishing through a webGIS application. Level-2 SST data are interpolated through a Co-Kriging algorithm, involving information from short term historical data, in order to retain as much information as possible. A modified gradient edge detection methodology is then applied to the interpolated products for the mesoscale feature extraction. The resulting datasets are served according to the Open Geospatial Consortium (OGC) standards and are available for visualization, processing and download though a dedicated web portal.