KEYWORDS: Point clouds, Biodiversity, 3D applications, LIDAR, Unmanned aerial vehicles, Data processing, RGB color model, Georeferencing, Receivers, Satellite navigation systems
The growing threat to biodiversity and ecosystem degradation necessitates innovative methods for monitoring and managing forested areas. This paper introduces the LIFE EL-BIOS project, a pioneering initiative to develop a Digital Twin for forest biodiversity analysis using terrestrial and airborne Light Detection and Ranging (LiDAR) technologies. The project utilizes advanced equipment, including the DJI Matrice 300 UAV with airborne LiDAR, DJI Mavic 3E, Quantum Systems Trinity F90+ with RGB and multispectral sensors, a GeoSLAM ZEB REVO terrestrial SLAM device, and a Leica BLK360 terrestrial laser scanner. Research spans over 40 forest plots, each 2000 square meters, in Greece's Kotychi-Strofilia Wetlands and Northern Pindos National Parks. The methodology integrates and georeferences point clouds from aerial and terrestrial sources to create unified point clouds for each area. Advanced software tools, such as 3DFIN and 3DFOREST, are then used to extract precise biodiversity-relevant parameters. This innovative data extraction method is compared with traditional in-situ measurements to evaluate the potential and limitations of the Digital Twin approach. A preliminary assessment focused on the time- and cost-effectiveness, accuracy, and robustness of this multiscale Earth Observation (EO) based mapping framework. Initial results suggest that the combined use of terrestrial and airborne LiDAR, multispectral data, and advanced analysis pipelines enhances the accuracy and speed of biodiversity measurements. Moreover, it allows for the extraction of additional information critical for developing biodiversity indicators. This study highlights the potential of multiscale and multisource EO data in creating digital twins of ecologically sensitive areas, offering a revolutionary approach to environmental conservation.
The aim of this study is the design and development of a conceptual and methodological framework that can be used for monitoring the condition of urban and sub–Urban Green Infrastructure (UGI) and the associated anthropogenic or natural induced pressures and threats to UGI biodiversity. Within this framework this manuscript describes in detail the development of a digital smart toolbox, which integrates data and information from satellite imagery, in-situ sensors and a smart mobile application developed to collect scientific data from public. The platform emphasizes the public participation of the urban residents for the protection and conservation of the environment. All this multi-source data can used for the sustainable management and protection of the biodiversity of urban and sub-urban UGI through the web based digital platform. In detail the following research and development activities were implemented. Originally the potential pressures and threats for the UGI biodiversity were identified and evaluated. Robust and transferable indicators for monitoring urban biodiversity using Earth Observation (EO) data were also formulated and developed. Different satellite EO data processing algorithms for the monitoring of potential pressures and threats to UGI biodiversity were also explored. Mobile sensors for data acquisition through citizen science to monitor biodiversity pressures and threats in UGI were also deployed. Finally, the integrated web-based platform was developed, that can be used to integrate data and provide information to the public and the authorities.
The international community has recently agreed on the need to address global challenges related to environmental degradation, climate change, poverty, inequality, prosperity, and peace and justice. The United Nations Agenda 2030 sets 17 Sustainable Development Goals (SDGs) that are monitored through 169 societal targets and 232 Indicators that should be accomplished till 2030, in order to ensure sustainability of the systems and the resources for the future generations. Monitoring of this progress can be implemented through the concept of the Essential Variables (EVs) defined as the minimum set of variables required to characterize a change of a system. Remote Sensing, providing multi-scale, multispectral and multi-temporal wide coverage of earth’s surface, can facilitate the monitoring of EVs trends over space and time. While global initiatives and research projects are currently work on streamlining the use of remote sensing data to the SDGs and EVs monitoring process, challenges exist on the identification and the selection of the proper variables and Indicators as well as on the efficient processing of large data volumes delivering robust and comprehensible information to policy makers and managers. This study serves as a pilot for the use of EVs quantifying changes in two Indicators of SDGs over terrestrial (SDG 15) and marine ecosystems (SDG 6). Two different Mediterranean sites are selected, and a process based on multi-temporal datasets of freely available satellite imagery is used in order to identify the trends for the selected Indicators.
The concept of Essential Variables (EVs) has emerged within the remote sensing community in recent years. The EVs, having previously defined as a minimal set of variables that determines the system’s state and development, have attracted considerable interest not only for remote sensing scientists, but from several, diverse thematic groups and communities. The driving forces behind this evolution, relates primary to the need to support national to global monitoring, reporting, research, and forecasting of complex earth systems, to the necessity for an essential set of parameters that could be used for monitoring progress towards the goals of different thematic communities as well as to the requirement to support consistent, objective temporal information provision for policy development and implementation. Also, considering the availability of sensor data with similar characteristics from different satellites orbiting around earth, there is a need to standardize the information extracted, independently of the observational platform and the processing algorithms as well as to provide this information in a more streamlined, comprehensible form to end-users not well acquainted with the remote sensing technology and terminology. So far, EVs have been introduced and adopted for monitoring oceans, climate and biodiversity systems as well as measuring progress towards UN Sustainable Development Goals (SDGs) implementation, while several other communities are in the process of adopting this concept in their domain. This study will review the recent progress as well as the current challenges and future developments in the research agenda around EVs. In particular we review the current state of EVs and their connection to the different scientific communities, as well as cross-domain interactions and synergies. We then describe potential new thematic areas and scientific communities where the concept of EVs could be applied and provide the outline of the process to be followed for identifying these variables.
Global climate changes are a main factor of risk for infrastructures and people living along the coasts around the world. In this context, sea level rise, coastal retreat and storm surges pose serious threats to coastal zones. In order to assess the expected coastal changes for the next decades, a detailed knowledge of the site’s topography (coastline position, DTM, bathymetry) is needed. This paper focuses on the use of very high resolution satellite data and UAV imagery for the generation of accurate very-high and ultra-high mapping of coastal areas. In addition, the use of very high resolution multi-spectral satellite data is investigated for the generation of coastal bathymetry maps. The paper presents a study for the island of Lipari and the coasts of Cinque Terre (Italy) and the island of Lefkas (Greece). For Lefkas, two areas of the island were mapped (the city of Lefkas and its adjoining lagoon in the north side of the island, and the Bay of Vasiliki at the south part of the island) using World View 1, and Wolrd View 3 satellite images, and UAV imagery. The satellite processing provided results that demonstrated an accuracy of approximately 0.25 m plannimetrically and 0.70 m vertically. The processing of the UAV imagery resulted in the generation of DTMs and orthophotos with an accuracy of approximately 0.03-0.04 meters. In addition, for the Vasiliki bay in the south of the island the World View 3 imagery was used for the estimation of a bathymetry map of the bay. The achieved results yielded an accuracy of 0.4 m. For the sites of Lipari and Cinque Terre (both in Italy), UAV surveys allowed to extract a DTM at about 2 cm of pixel resolution. The integration of topographic data with high resolution multibeam bathymetry and expected sea level rise from IPCC AR5 2.6 and 8.5 climatic scenarios, will be used to map sea level rise scenarios for 2050 and 2100, taking into account the Vertical Land Motion (VLM) as estimated from CGPS data. The above-mentioned study was realized during the implementation of the SAVEMEDCOASTS project (Sea level rise scenarios along the Mediterranean coasts, funded by the European Commission ECHO A.5, GA ECHO/SUB/2016/742473/PREV16, www.savemedcoasts.eu).
Urban environmental management is of profound importance due to increasing urban development alongside the need to develop resilient cities and sustainable urbanization strategies. Spatial explicit urban environmental quality indices can provide policy makers and the public with valuable information for urban planning and policy formation. The aim of this study is the development of a multi-component urban environmental quality index for the metropolitan area of Thessaloniki. The approach was designed to be robust and easily transferred across cities with similar characteristics. Land Surface Temperature (LST) was estimated based on multi-seasonal Landsat-8 images, while Fractional Vegetation Cover (FVC) was derived from fused Sentinel-2 images and validated using WorldView-2 very high spatial resolution imagery. In addition, several geospatial layers related to atmospheric pollution, petroleum refineries, noise pollution, urban density and distance to green infrastructures were processed within GIS environment and integrated with the satellite extracted information. A multi-criteria Analytical Hierarchical Approach (AHP) was used for integrating the sub-criteria to a final urban environmental quality index using weights from expert knowledge and literature review. The results identified extended areas in the western part of the study region as well as several hot spots in the eastern part, that local planners should develop and implement actions for improving living conditions of residents. Overall, the method proved to be viable and flexible and its application can be expanded to similar Mediterranean cities.
Within the field of forestry, forest road mapping and inventory plays an important role in management activities related to wood harvesting industry, sentiment and water run-off modelling, biodiversity distribution and ecological connectivity, recreation activities, future planning of forest road networks and wildfire protection and fire-fighting. Especially in countries of the Mediterranean Rim, knowledge at regional and national scales regarding the distribution and the characteristics of rural and forest road network is essential in order to ensure an effective emergency management and rapid response of the fire-fighting mechanism. Yet, the absence of accurate and updated geodatabases and the drawbacks related to the use of traditional cartographic methods arising from the forest environment settings, and the cost and efforts needed, as thousands of meters need to be surveyed per site, trigger the need for new data sources and innovative mapping approaches. Monitoring the condition of unpaved forest roads with unmanned aerial vehicle technology is an attractive option for substituting objective, laboursome surveys. Although photogrammetric processing of UAV imagery can achieve accuracy of 1-2 centimeters and dense point clouds, the process is commonly based on the establishment of control points. In the case of forest road networks, which are linear features, there is a need for a great number of control points. Our aim is to evaluate low-cost UAV orthoimages generated over forest areas with GCP’s captured from existing national scale aerial orthoimagery, satellite imagery available through a web mapping service (WMS), field surveys using Mobile Mapping System and GNSS receiver. We also explored the direct georeferencing potential through the GNSS onboard the low cost UAV. The results suggest that the GNSS approach proved to most accurate, while the positional accuracy derived using the WMS and the aerial orthoimagery datasets deemed satisfactory for the specific task at hand. The direct georeferencing procedure seems to be insufficient unless an onboard GNSS with improved specifications or Real-Time Kinematic (RTK) capabilities is used.
Linear features abound in man-made environments and the possibility of their automated detection and measurement on digital images renders their employment -- rather than that of point features -- highly advantageous for camera calibration, space resection, relative orientation and object reconstruction, particularly in close-range photogrammetry and computer vision. This paper presents our formulation and treatment of mathematical models suitable for the tasks of relative orientation of image triples and for object reconstruction, up to a scale factor, from straight line correspondences, a problem known as `motion and structure' in computer vision. In this phase, the formulated algorithms have been extensively investigated with simulations employing various basic line configurations in order to further illuminate the still inadequately addressed questions of critical geometries and degeneracy. Conclusions are reported for several degenerate combinations of object line distributions and perspective center position patterns which have a particular interest. Finally, a simulated numerical example is also given.
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