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Keywords = geodata visualization

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28 pages, 4307 KB  
Article
A 3D WebGIS Open-Source Prototype for Bridge Inspection Data Management
by Federica Gaspari, Rebecca Fascia, Federico Barbieri, Oscar Roman, Daniela Carrion and Livio Pinto
Geomatics 2025, 5(4), 68; https://doi.org/10.3390/geomatics5040068 - 24 Nov 2025
Viewed by 1136
Abstract
In response to the increasing demand for effective bridge management and the shortcomings of current proprietary solutions, this work presents an open-source, web-based platform designed to support bridge inspection and data management, particularly for small and medium-sized public administrations, which often lack personnel [...] Read more.
In response to the increasing demand for effective bridge management and the shortcomings of current proprietary solutions, this work presents an open-source, web-based platform designed to support bridge inspection and data management, particularly for small and medium-sized public administrations, which often lack personnel or funding for implementing context-specific tools. The system addresses fragmented workflows by integrating multi-format geospatial and 3D data—such as point clouds, CAD/BIM models, and georeferenced imagery—within a unified, modular architecture. The platform enables structured inventory, interactive 2D/3D visualization, defect annotation, and role-based user interaction, aligning with FAIR principles and interoperability standards. Built entirely with free and open-source tools, the P.O.N.T.I. prototype ensures scalability, transparency, and adaptability. A multi-layer navigation interface guides users through asset exploration, inspection history, and immersive 3D viewers. Fully documented and publicly available on GitHub, the system allows for deployment across varying institutional contexts. The platform’s design anticipates future developments, including integration with IoT monitoring systems, AI-driven inspection tools, and chatbot interfaces for natural language querying. By overcoming existing proprietary limitations and providing access to a versatile single space, the proposed solution supports decision-makers in the digital transition towards a more accessible, transparent and integrated infrastructure asset management. Full article
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16 pages, 4572 KB  
Article
Models of Geospatially Referenced People Distribution as a Basis for Studying the Daily Cycles of Urban Infrastructure Use by Residents
by Danila Parygin, Alexander Anokhin, Anton Anikin, Anton Finogeev and Alexander Gurtyakov
Smart Cities 2025, 8(1), 1; https://doi.org/10.3390/smartcities8010001 - 24 Dec 2024
Cited by 1 | Viewed by 1406
Abstract
City services and infrastructures are focused on consumers and are able to effectively and qualitatively implement their functions only under conditions of normal workload. In this regard, the correct organization of a public service system is directly related to the knowledge of the [...] Read more.
City services and infrastructures are focused on consumers and are able to effectively and qualitatively implement their functions only under conditions of normal workload. In this regard, the correct organization of a public service system is directly related to the knowledge of the quantitative and qualitative composition of people in the city during the day. The article discusses existing solutions for analyzing the distribution of people in a territory based on data collected by mobile operators, payment terminals, navigation systems and other network solutions, as well as the modeling methods derived from them. The scientific aim of the study is to propose a solution for modeling the daily distribution of people based on open statistics collected from the Internet and open-web mapping data. The stages of development of the modeling software environment and the methods for spatial analysis of available data on a digital cartographic basis are described. The proposed approach includes the use of archetypes of social groups, occupational statistics, gender and age composition of a certain territory, as well as the characteristics of urban infrastructure objects in terms of composition and purpose. Solutions for modeling the 48 h distribution of city residents with reference to certain infrastructure facilities (residential, public and working) during working and weekend days with an hourly breakdown of the simulated values were created as a result of the study. A simulation of the daily distribution of people in the city was carried out using the example of the city of Volgograd, Russian Federation. A picture of the daily distribution of city residents by district and specific buildings of the city was obtained as a result of the modeling. The proposed approach and the created algorithm can be applied to any city. Full article
(This article belongs to the Section Applied Science and Humanities for Smart Cities)
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20 pages, 2951 KB  
Article
Spatial Visualization Based on Geodata Fusion Using an Autonomous Unmanned Vessel
by Marta Włodarczyk-Sielicka, Dawid Połap, Katarzyna Prokop, Karolina Połap and Andrzej Stateczny
Remote Sens. 2023, 15(7), 1763; https://doi.org/10.3390/rs15071763 - 25 Mar 2023
Cited by 13 | Viewed by 2488
Abstract
The visualization of riverbeds and surface facilities on the banks is crucial for systems that analyze conditions, safety, and changes in this environment. Hence, in this paper, we propose collecting, and processing data from a variety of sensors—sonar, LiDAR, multibeam echosounder (MBES), and [...] Read more.
The visualization of riverbeds and surface facilities on the banks is crucial for systems that analyze conditions, safety, and changes in this environment. Hence, in this paper, we propose collecting, and processing data from a variety of sensors—sonar, LiDAR, multibeam echosounder (MBES), and camera—to create a visualization for further analysis. For this purpose, we took measurements from sensors installed on an autonomous, unmanned hydrographic vessel, and then proposed a data fusion mechanism, to create a visualization using modules under and above the water. A fusion contains key-point analysis on classic images and sonars, augmentation/reduction of point clouds, fitting data and mesh creation. Then, we also propose an analysis module that can be used to compare and extract information from created visualizations. The analysis module is based on artificial intelligence tools for the classification tasks, which helps in further comparison to archival data. Such a model was tested using various techniques to achieve the fastest and most accurate visualizations possible in simulation and real case studies. Full article
(This article belongs to the Topic Machine Learning in Internet of Things)
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23 pages, 58630 KB  
Article
Using Flickr Data to Understand Image of Urban Public Spaces with a Deep Learning Model: A Case Study of the Haihe River in Tianjin
by Chenghao Yang, Tongtong Liu and Shengtian Zhang
ISPRS Int. J. Geo-Inf. 2022, 11(10), 497; https://doi.org/10.3390/ijgi11100497 - 21 Sep 2022
Cited by 11 | Viewed by 6201
Abstract
Understanding public perceptions of images of urban public spaces can guide efforts to improve urban vitality and spatial diversity. The rise of social media data and breakthroughs in deep learning frameworks for computer vision provide new opportunities for studying public perceptions in public [...] Read more.
Understanding public perceptions of images of urban public spaces can guide efforts to improve urban vitality and spatial diversity. The rise of social media data and breakthroughs in deep learning frameworks for computer vision provide new opportunities for studying public perceptions in public spaces. While social media research methods already exist for extracting geo-information on public preferences and emotion analysis findings from geodata, this paper aims at deep learning analysis by building a VGG-16 image classification method that enhanced the research content of images without geo-information. In this study, 1940 Flickr images of the Haihe River in Tianjin were identified in multiple scenes with deep learning. The regularized VGG-16 architecture showed high accuracies of 81.75% for the TOP-1 and 96.75% for the TOP-5 and Grad-CAM visualization modules for the interpretation of classification results. The result of the present work indicate that images of the Haihe River are dominated by skyscrapers, bridges, promenades, and urban canals. After using kernel density to visualize the spatial distribution of Flickr images with geodata, it was found that there are three vitality areas in Haihe River. However, the kernel density result also shows that judging spatial visualization based solely on geodata is incomplete. The spatial distribution can be used as an assistant function in the case of the under-representation of geodata. Collectively, the field of how to apply computer vision to urban design research was explored and extended in this trial study. Full article
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5 pages, 212 KB  
Editorial
Editorial on the Citizen Science and Geospatial Capacity Building
by Sultan Kocaman, Sameer Saran, Murat Durmaz and Senthil Kumar
ISPRS Int. J. Geo-Inf. 2021, 10(11), 741; https://doi.org/10.3390/ijgi10110741 - 1 Nov 2021
Cited by 4 | Viewed by 2470
Abstract
This article introduces the Special Issue on “Citizen Science and Geospatial Capacity Building” and briefly evaluates the future trends in this field. This Special Issue was initiated for emphasizing the importance of citizen science (CitSci) and volunteered geographic information (VGI) in various stages [...] Read more.
This article introduces the Special Issue on “Citizen Science and Geospatial Capacity Building” and briefly evaluates the future trends in this field. This Special Issue was initiated for emphasizing the importance of citizen science (CitSci) and volunteered geographic information (VGI) in various stages of geodata collection, processing, analysis and visualization; and for demonstrating the capabilities and advantages of both approaches. The topic falls well within the main focus areas of ISPRS Commission V on Education and Outreach. The articles collected in the issue have shown the enormously wide application fields of geospatial technologies, and the need of CitSci and VGI support for efficient information extraction and synthesizing. They also pointed out various problems encountered during these processes. The needs and future research directions in this subject can broadly be categorized as; (a) data quality issues especially in the light of big data; (b) ontology studies for geospatial data suited for diverse user backgrounds, data integration, and sharing; (c) development of machine learning and artificial intelligence based online tools for pattern recognition and object identification using existing repositories of CitSci and VGI projects; and (d) open science and open data practices for increasing the efficiency, decreasing the redundancy, and acknowledgement of all stakeholders. Full article
(This article belongs to the Special Issue Citizen Science and Geospatial Capacity Building)
23 pages, 6588 KB  
Article
Large-Area Empirically Based Visual Landscape Quality Assessment for Spatial Planning—A Validation Approach by Method Triangulation
by Michael Roth, Silvio Hildebrandt, Ulrich Walz and Wolfgang Wende
Sustainability 2021, 13(4), 1891; https://doi.org/10.3390/su13041891 - 9 Feb 2021
Cited by 12 | Viewed by 4018
Abstract
Large area visual landscape quality assessment, especially at the national level is needed to answer the demand from strategic planning. In our paper, we describe and compare two recent modelling approaches for this task regarding their theoretical and empirical basis, resolution, model configuration [...] Read more.
Large area visual landscape quality assessment, especially at the national level is needed to answer the demand from strategic planning. In our paper, we describe and compare two recent modelling approaches for this task regarding their theoretical and empirical basis, resolution, model configuration and results. To compare the outcomes of the two methods, both correlation measures and a visual overlay analysing the inversions are used. The results show, that despite the different methodological approaches, in over 90% of the area of Germany there are only minor deviations between the resulting scenic quality maps (less or equal one step on a five-step scale). The main differences occur due to a different relative weight given to terrain and water indicators in the respective methods. We conclude that a methodologically valid scenic quality evaluation using geodata of homogenous quality is possible also at the national level. By triangulating between different methods, for both, the validity could be proven. The datasets elaborated can also be used as a benchmark for regional landscape assessments and for an upcoming monitoring of changes in visual landscape quality. Full article
(This article belongs to the Special Issue Visual Landscape Research in Sustainable Urban and Landscape Planning)
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24 pages, 3185 KB  
Article
How Society 5.0 and Industry 4.0 Ideas Shape the Open Data Performance Expectancy
by Anna Sołtysik-Piorunkiewicz and Iwona Zdonek
Sustainability 2021, 13(2), 917; https://doi.org/10.3390/su13020917 - 18 Jan 2021
Cited by 61 | Viewed by 6497
Abstract
The open data (OD) performance expectancy is a critical factor for the user technology acceptance models for future implementation OD in Industry 4.0, and to have an impact in area of Society 5.0. The purpose of this article is identifying trends and key [...] Read more.
The open data (OD) performance expectancy is a critical factor for the user technology acceptance models for future implementation OD in Industry 4.0, and to have an impact in area of Society 5.0. The purpose of this article is identifying trends and key words (leading terms) in promoting ODs for their use in Industry 4.0 and Society 5.0. We are also looking for leaders in Europe in promoting the use of OD in the context of Industry 4.0 and Society 5.0. The research methodology includes methods such as: analyses based on text mining, visualization techniques, and multidimensional cluster analyses with correlation analyses. The dataset covered 288 digital products and services based on OD. The timeframe covers the period January 2018–January 2020, and the research focuses on European issues. The research is focused on texts promoting the digital OD products and services, with the most popular being applications, websites and platforms. The main direction in presenting the benefits of their use is related to promoting them as tools to provide real time information on public issues, primarily in areas such as transport, education, culture and sport, economics and finance and health. The main types of OD are geodata and those specified as national and local. Additionally, the geographical area in Europe-dominating countries, and the key terms promoting product and services in context of OD performance expectancy in Western Europe, Northern Europe, Southern Europe and Eastern Europe, were found. Full article
(This article belongs to the Special Issue Society 5.0 and Industry 4.0 Relations and Implications)
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17 pages, 5789 KB  
Article
A Study of User Activity Patterns and the Effect of Venue Types on City Dynamics Using Location-Based Social Network Data
by Naimat Ullah Khan, Wanggen Wan, Shui Yu, A. A. M. Muzahid, Sajid Khan and Li Hou
ISPRS Int. J. Geo-Inf. 2020, 9(12), 733; https://doi.org/10.3390/ijgi9120733 - 7 Dec 2020
Cited by 13 | Viewed by 4198
Abstract
The main purpose of this research is to study the effect of various types of venues on the density distribution of residents and model check-in data from a Location-Based Social Network for the city of Shanghai, China by using combination of multiple temporal, [...] Read more.
The main purpose of this research is to study the effect of various types of venues on the density distribution of residents and model check-in data from a Location-Based Social Network for the city of Shanghai, China by using combination of multiple temporal, spatial and visualization techniques by classifying users’ check-ins into different venue categories. This article investigates the use of Weibo for big data analysis and its efficiency in various categories instead of manually collected datasets, by exploring the relation between time, frequency, place and category of check-in based on location characteristics and their contributions. The data used in this research was acquired from a famous Chinese microblogs called Weibo, which was preprocessed to get the most significant and relevant attributes for the current study and transformed into Geographical Information Systems format, analyzed and, finally, presented with the help of graphs, tables and heat maps. The Kernel Density Estimation was used for spatial analysis. The venue categorization was based on nature of the physical locations within the city by comparing the name of venue extracted from Weibo dataset with the function such as education for schools or shopping for malls and so on. The results of usage patterns from hours to days, venue categories and frequency distribution into these categories as well as the density of check-in within the Shanghai and contribution of each venue category in its diversity are thoroughly demonstrated, uncovering interesting spatio-temporal patterns including frequency and density of users from different venues at different time intervals, and significance of using geo-data from Weibo to study human behavior in variety of studies like education, tourism and city dynamics based on location-based social networks. Our findings uncover various aspects of activity patterns in human behavior, the significance of venue classes and its effects in Shanghai, which can be applied in pattern analysis, recommendation systems and other interactive applications for these classes. Full article
(This article belongs to the Special Issue Geodata Science and Spatial Analysis in Urban Studies)
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28 pages, 26554 KB  
Article
A Feasibility Study of Map-Based Dashboard for Spatiotemporal Knowledge Acquisition and Analysis
by Chenyu Zuo, Linfang Ding and Liqiu Meng
ISPRS Int. J. Geo-Inf. 2020, 9(11), 636; https://doi.org/10.3390/ijgi9110636 - 27 Oct 2020
Cited by 15 | Viewed by 8576
Abstract
Map-based dashboards are among the most popular tools that support the viewing and understanding of a large amount of geo-data with complex relations. In spite of many existing design examples, little is known about their impacts on users and whether they match the [...] Read more.
Map-based dashboards are among the most popular tools that support the viewing and understanding of a large amount of geo-data with complex relations. In spite of many existing design examples, little is known about their impacts on users and whether they match the information demand and expectations of target users. The authors first designed a novel map-based dashboard to support their target users’ spatiotemporal knowledge acquisition and analysis, and then conducted an experiment to assess the feasibility of the proposed dashboard. The experiment consists of eye-tracking, benchmark tasks, and interviews. A total of 40 participants were recruited for the experiment. The results have verified the effectiveness and efficiency of the proposed map-based dashboard in supporting the given tasks. At the same time, the experiment has revealed a number of aspects for improvement related to the layout design, the labeling of multiple panels and the integration of visual analytical elements in map-based dashboards, as well as future user studies. Full article
(This article belongs to the Special Issue Multimedia Cartography)
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26 pages, 6256 KB  
Article
A Framework Uniting Ontology-Based Geodata Integration and Geovisual Analytics
by Linfang Ding, Guohui Xiao, Diego Calvanese and Liqiu Meng
ISPRS Int. J. Geo-Inf. 2020, 9(8), 474; https://doi.org/10.3390/ijgi9080474 - 28 Jul 2020
Cited by 21 | Viewed by 7886
Abstract
In a variety of applications relying on geospatial data, getting insights into heterogeneous geodata sources is crucial for decision making, but often challenging. The reason is that it typically requires combining information coming from different sources via data integration techniques, and then making [...] Read more.
In a variety of applications relying on geospatial data, getting insights into heterogeneous geodata sources is crucial for decision making, but often challenging. The reason is that it typically requires combining information coming from different sources via data integration techniques, and then making sense out of the combined data via sophisticated analysis methods. To address this challenge we rely on two well-established research areas: data integration and geovisual analytics, and propose to adopt an ontology-based approach to decouple the challenges of data access and analytics. Our framework consists of two modules centered around an ontology: (1) an ontology-based data integration (OBDI) module, in which mappings specify the relationship between the underlying data and a domain ontology; (2) a geovisual analytics (GeoVA) module, designed for the exploration of the integrated data, by explicitly making use of standard ontologies. In this framework, ontologies play a central role by providing a coherent view over the heterogeneous data, and by acting as a mediator for visual analysis tasks. We test our framework in a scenario for the investigation of the spatiotemporal patterns of meteorological and traffic data from several open data sources. Initial studies show that our approach is feasible for the exploration and understanding of heterogeneous geospatial data. Full article
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23 pages, 9242 KB  
Article
Augmenting Printed School Atlases with Thematic 3D Maps
by Raimund Schnürer, Cédric Dind, Stefan Schalcher, Pascal Tschudi and Lorenz Hurni
Multimodal Technol. Interact. 2020, 4(2), 23; https://doi.org/10.3390/mti4020023 - 27 May 2020
Cited by 13 | Viewed by 7331
Abstract
Digitalization in schools requires a rethinking of teaching materials and methods in all subjects. This upheaval also concerns traditional print media, like school atlases used in geography classes. In this work, we examine the cartographic technological feasibility of extending a printed school atlas [...] Read more.
Digitalization in schools requires a rethinking of teaching materials and methods in all subjects. This upheaval also concerns traditional print media, like school atlases used in geography classes. In this work, we examine the cartographic technological feasibility of extending a printed school atlas with digital content by augmented reality (AR). While previous research rather focused on topographic three-dimensional (3D) maps, our prototypical application for Android tablets complements map sheets of the Swiss World Atlas with thematically related data. We follow a natural marker approach using the AR engine Vuforia and the game engine Unity. We compare two workflows to insert geo-data, being correctly aligned with the map images, into the game engine. Next, the imported data are transformed into partly animated 3D visualizations, such as a dot distribution map, curved lines, pie chart billboards, stacked cuboids, extruded bars, and polygons. Additionally, we implemented legends, elements for temporal and thematic navigation, a screen capture function, and a touch-based feature query for the user interface. We evaluated our prototype in a usability experiment, which showed that secondary school students are as effective, interested, and sustainable with printed as with augmented maps when solving geographic tasks. Full article
(This article belongs to the Special Issue 3D Human–Computer Interaction)
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20 pages, 1569 KB  
Review
Geospatial Data Management Research: Progress and Future Directions
by Martin Breunig, Patrick Erik Bradley, Markus Jahn, Paul Kuper, Nima Mazroob, Norbert Rösch, Mulhim Al-Doori, Emmanuel Stefanakis and Mojgan Jadidi
ISPRS Int. J. Geo-Inf. 2020, 9(2), 95; https://doi.org/10.3390/ijgi9020095 - 4 Feb 2020
Cited by 153 | Viewed by 26099
Abstract
Without geospatial data management, today’s challenges in big data applications such as earth observation, geographic information system/building information modeling (GIS/BIM) integration, and 3D/4D city planning cannot be solved. Furthermore, geospatial data management plays a connecting role between data acquisition, data modelling, data visualization, [...] Read more.
Without geospatial data management, today’s challenges in big data applications such as earth observation, geographic information system/building information modeling (GIS/BIM) integration, and 3D/4D city planning cannot be solved. Furthermore, geospatial data management plays a connecting role between data acquisition, data modelling, data visualization, and data analysis. It enables the continuous availability of geospatial data and the replicability of geospatial data analysis. In the first part of this article, five milestones of geospatial data management research are presented that were achieved during the last decade. The first one reflects advancements in BIM/GIS integration at data, process, and application levels. The second milestone presents theoretical progress by introducing topology as a key concept of geospatial data management. In the third milestone, 3D/4D geospatial data management is described as a key concept for city modelling, including subsurface models. Progress in modelling and visualization of massive geospatial features on web platforms is the fourth milestone which includes discrete global grid systems as an alternative geospatial reference framework. The intensive use of geosensor data sources is the fifth milestone which opens the way to parallel data storage platforms supporting data analysis on geosensors. In the second part of this article, five future directions of geospatial data management research are presented that have the potential to become key research fields of geospatial data management in the next decade. Geo-data science will have the task to extract knowledge from unstructured and structured geospatial data and to bridge the gap between modern information technology concepts and the geo-related sciences. Topology is presented as a powerful and general concept to analyze GIS and BIM data structures and spatial relations that will be of great importance in emerging applications such as smart cities and digital twins. Data-streaming libraries and “in-situ” geo-computing on objects executed directly on the sensors will revolutionize geo-information science and bridge geo-computing with geospatial data management. Advanced geospatial data visualization on web platforms will enable the representation of dynamically changing geospatial features or moving objects’ trajectories. Finally, geospatial data management will support big geospatial data analysis, and graph databases are expected to experience a revival on top of parallel and distributed data stores supporting big geospatial data analysis. Full article
(This article belongs to the Special Issue State-of-the-Art in Spatial Information Science)
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18 pages, 8750 KB  
Article
Automatic Geodata Processing Methods for Real-World City Visualizations in Cities: Skylines
by Jan Pinos, Vit Vozenilek and Ondrej Pavlis
ISPRS Int. J. Geo-Inf. 2020, 9(1), 17; https://doi.org/10.3390/ijgi9010017 - 1 Jan 2020
Cited by 19 | Viewed by 19430
Abstract
The city-building game Cities: Skylines simulates urban-related processes in a visually appealing 3D environment and thus offers interesting possibilities for visualizations of real-world places. Such visualizations could be used for presentation, participation, or education projects. However, the creation process of the game model [...] Read more.
The city-building game Cities: Skylines simulates urban-related processes in a visually appealing 3D environment and thus offers interesting possibilities for visualizations of real-world places. Such visualizations could be used for presentation, participation, or education projects. However, the creation process of the game model from geographical data is inaccurate, complicated, and time consuming, thus preventing the wider use of this game for non-entertainment purposes. This paper presents the automatic methods scripted in the Cities: Skylines application programming interface (API) and bundled into a game modification (commonly referred to as a game mod) named GeoSkylines, to create a geographically accurate visualization of real-world places in Cities: Skylines. Based on various geographical data, the presented methods create road and rail networks, tree coverage, water basins, planning zones, buildings, and services. Using these methods, playable models of the cities of Svit (Slovakia) and Olomouc (Czech Republic) were created in the game. The game mod GeoSkylines also provides methods for exporting game objects such as roads, buildings, and zones into a Geographic Information System (GIS) data format that can be processed further. This feature enables the game Cities: Skylines to be utilized as a data collection tool that could be used in redevelopment design projects. Full article
(This article belongs to the Special Issue Gaming and Geospatial Information)
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22 pages, 8287 KB  
Article
Comparison of GNSS-, TLS- and Different Altitude UAV-Generated Datasets on the Basis of Spatial Differences
by Huseyin Yurtseven
ISPRS Int. J. Geo-Inf. 2019, 8(4), 175; https://doi.org/10.3390/ijgi8040175 - 3 Apr 2019
Cited by 27 | Viewed by 8970
Abstract
In this study, different in-situ and close-range sensing surveying techniques were compared based on the spatial differences of the resultant datasets. In this context, the DJI Phantom 3 Advanced and Trimble UX5 Unmanned Aerial Vehicle (UAV) platforms, Zoller + Fröhlich 5010C phase comparison [...] Read more.
In this study, different in-situ and close-range sensing surveying techniques were compared based on the spatial differences of the resultant datasets. In this context, the DJI Phantom 3 Advanced and Trimble UX5 Unmanned Aerial Vehicle (UAV) platforms, Zoller + Fröhlich 5010C phase comparison for continuous wave-based Terrestrial Laser Scanning (TLS) system and Network Real Time Kinematic (NRTK) Global Navigation Satellite System (GNSS) receiver were used to obtain the horizontal and vertical information about the study area. All data were collected in a gently (mean slope angle 4%) inclined, flat vegetation-free, bare-earth valley bottom near Istanbul, Turkey (the size is approximately 0.7 ha). UAV data acquisitions were performed at 25-, 50-, 120-m (with DJI Phantom 3 Advanced) and 350-m (with Trimble UX5) flight altitudes (above ground level, AGL). The imagery was processed with the state-of-the-art SfM (Structure-from-Motion) photogrammetry software. The ortho-mosaics and digital elevation models were generated from UAV-based photogrammetric and TLS-based data. GNSS- and TLS-based data were used as reference to calculate the accuracy of the UAV-based geodata. The UAV-results were assessed in 1D (points), 2D (areas) and 3D (volumes) based on the horizontal (X- and Y-directions) and vertical (Z-direction) differences. Various error measures, including the RMSE (Root Mean Square Error), ME (Mean Error) or MAE (Mean Average Error), and simple descriptive statistics were used to calculate the residuals. The comparison of the results is simplified by applying a normalization procedure commonly used in multi-criteria-decision-making analysis or visualizing offset. According to the results, low-altitude (25 and 50 m AGL) flights feature higher accuracy in the horizontal dimension (e.g., mean errors of 0.085 and 0.064 m, respectively) but lower accuracy in the Z-dimension (e.g., false positive volumes of 2402 and 1160 m3, respectively) compared to the higher-altitude flights (i.e., 120 and 350 m AGL). The accuracy difference with regard to the observed terrain heights are particularly striking, depending on the compared error measure, up to a factor of 40 (i.e., false positive values for 120 vs. 50 m AGL). This error is attributed to the “doming-effect”—a broad-scale systematic deformation of the reconstructed terrain surface, which is commonly known in SfM photogrammetry and results from inaccuracies in modeling the radial distortion of the camera lens. Within the scope of the study, the “doming-effect” was modeled as a functional surface by using the spatial differences and the results were indicated that the “doming-effect” increases inversely proportional to the flight altitude. Full article
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22 pages, 5245 KB  
Article
Geo-Tagged Social Media Data-Based Analytical Approach for Perceiving Impacts of Social Events
by Ruoxin Zhu, Diao Lin, Michael Jendryke, Chenyu Zuo, Linfang Ding and Liqiu Meng
ISPRS Int. J. Geo-Inf. 2019, 8(1), 15; https://doi.org/10.3390/ijgi8010015 - 29 Dec 2018
Cited by 31 | Viewed by 9110
Abstract
Studying the impact of social events is important for the sustainable development of society. Given the growing popularity of social media applications, social sensing networks with users acting as smart social sensors provide a unique channel for understanding social events. Current research on [...] Read more.
Studying the impact of social events is important for the sustainable development of society. Given the growing popularity of social media applications, social sensing networks with users acting as smart social sensors provide a unique channel for understanding social events. Current research on social events through geo-tagged social media is mainly focused on the extraction of information about when, where, and what happened, i.e., event detection. There is a trend towards the machine learning of more complex events from even larger input data. This research work will undoubtedly lead to a better understanding of big geo-data. In this study, however, we start from known or detected events, raising further questions on how they happened, how they affect people’s lives, and for how long. By combining machine learning, natural language processing, and visualization methods in a generic analytical framework, we attempt to interpret the impact of known social events from the dimensions of time, space, and semantics based on geo-tagged social media data. The whole analysis process consists of four parts: (1) preprocessing; (2) extraction of event-related information; (3) analysis of event impact; and (4) visualization. We conducted a case study on the “2014 Shanghai Stampede” event on the basis of Chinese Sina Weibo data. The results are visualized in various ways, thus ensuring the feasibility and effectiveness of our proposed framework. Both the methods and the case study can serve as decision references for situational awareness and city management. Full article
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