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An Efficient Representation of Quadtrees and Bintrees for Multiresolution Terrain Models

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Geo-Spatial Information Science 2011年第3期14卷 198-206页

作者： Yusnier Valle José Ortiz center of geoinformatics and Digital Signals University of Informatics Sciences Dean of the Faculty 1 University of Informatics Sciences

A space-filling curve in 2,3,or higher dimensions can be thought as a path of a continuously moving *** its main goal is to preserve spatial proximity,this type of curves has been widely used in the design and implementation of spatial data structures and nearest neighbor-finding *** paper is essentially focused on the efficient representation of Digital Ele-vation Models(DEM) that entirely fit into the main *** propose a new hierarchical quadtree-like data structure to be built over domains of unrestricted size,and a representation of a quadtree and a binary triangles tree by means of the Hilbert and the Sierpinski space-filling curves,respectively,taking into account the hierarchical nature and the clustering properties of this kind of *** triangulation schemes are described for the space-filling-curves-based approaches to efficiently visualize multiresolu-tion surfaces.

关键词： bintrees quadtrees space-filling curves spatial data structures digital terrain models

Comprehensive assessment of real-time precise products from IGS analysis centers

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Satellite Navigation 2022年第1期3卷 97-113,I0004页

作者： Bofeng Li Haibo Ge Yuhang Bu Yanning Zheng Leitong Yuan College of Surveying and geoinformatics Tongji UniversityShanghai 200092China

Real-Time Precise Point Positioning(RT-PPP)has been one of the research hotspots in GNSS(Global Navigation Satellite System)community for ***-time precise products of satellite orbits and clocks are the prerequisite for ***,it is of great importance to investigate the current multi-GNSS real-time precise products in State Space Representation(SSR)from diferent analysis *** this article,SSR products from 10 analysis centers are comprehensively evaluated by comparing them with the fnal products and performing the kinematic *** results show that analysis centers CNES(Centre National D’Etudes Spatiales)and WHU(GNSS Research center of Wuhan University)provide the most complete products with the best *** the accuracy of real-time products for the GNSSs,the accuracies of orbit and clock products are better than 5 cm and 0.15 ns,respectively,for Global Positioning System(GPS),followed by Galileo navigation satellite system(Galileo),BeiDou-3 Navigation Satellite System(BDS-3),GLObal NAvigation Satellite System(GLONASS),and BeiDou-2 Navigation Satellite System(BDS-2).Meanwhile,the results of the RT-PPP with quad-system show that the positioning accuracies are 1.76,1.12 and 2.68 cm in east,north,and up directions,respectively,and the convergence time to 0.1,0.1,0.2 m for corresponding directions is 15.35 min.

关键词： Real-time precise point positioning(RT-PPP) State space representation(SSR) Multi-GNSS Convergence time

Deep reinforcement learning and 3D physical environments applied to crowd evacuation in congested scenarios

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International Journal of Digital Earth 2023年第1期16卷 691-714页

作者： Dong Zhang Wenhang Li Jianhua Gong Guoyong Zhang Jiantao Liu Lin Huang Heng Liu Haonan Ma National Engineering Research center for geoinformatics Aerospace Information Research InstituteChinese Academy of SciencesBeijingPeople’s Republic of China University of Chinese Academy of Sciences BeijingPeople’s Republic of China Zhejiang-CAS Application center for geoinformatics JiaxingPeople’s Republic of China School of Surveying and Geo-Informatics Shandong Jianzhu UniversityJinanPeople’s Republic of China

To avoid crowd evacuation simulations depending on 2D environments and real data,we propose a framework for crowd evacuation modeling and simulation by applying deep reinforcement learning(DRL)and 3D physical environments(3DPEs).In 3DPEs,we construct simulation scenarios from the aspects of geometry,semantics and physics,which include the environment,the agents and their interactions,and provide training samples for *** DRL,we design a double branch feature extraction combined actor and critic network as the DRL policy and value function and use a clipped surrogate objective with polynomial decay to update the *** a unified configuration,we conduct evacuation *** scenarios with one exit,we reproduce and verify the bottleneck effect of congested crowds and explore the impact of exit width and agent characteristics(number,mass and height)on *** scenarios with two exits and a uniform(nonuniform)distribution of agents,we explore the impact of exit characteristics(width and relative position)and agent characteristics(height,initial location and distribution)on agent exit selection and ***,interactive 3DPEs and unified DRL enable agents to adapt to different evacuation scenarios to simulate crowd evacuation and explore the laws of crowd evacuation.

关键词： Virtual geographic environments crowd evacuation crowd evacuation simulation deep reinforcement learning 3D physical environments

Selected issues of cartographic communication optimization for emergency centers

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International Journal of Digital Earth 2010年第4期3卷 316-339页

作者： Karel Staněk Lucie Friedmannová Petr Kubıcek Milan Konecný Laboratory on geoinformatics and Cartography Department of GeographyFaculty of ScienceMasaryk UniversityBrnoCzech Republic

Cartographic communication and support within emergency management(EM)are complicated issues with changing demands according to the incident extent and phase of the EM *** in mind the specifics of each purpose,it is obvious that spatial data used for maps preparation and production must be differently visualized even for the same type of emergency incident(traffic accident,fire,and natural disaster).Context-based cartography is a promising methodology to deal with the changing demands of an operational EM *** overview of cartographic communication is presented within the context of an operational EM center,activities of particular actors,and map use supporting the incident *** authors of the paper respond to a series of questions,for example:what is the current cartographic support of operational EM in the Czech Republic in Digital Earth conditions?What possibilities are there to improve the cartographic communication?How can contextual cartographic services be implemented in a Web environment and how can the usability of results be tested?The paper gives several examples of the usage of cartographic technologies in map creation for various emergency situations.

关键词： map use cartographic communication context-based cartography Digital Earth operational emergency management

Retrieval of sea surface winds under hurricane conditions from GNSS-R observations

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Acta Oceanologica Sinica 2016年第9期35卷 91-97页

作者： JING Cheng YANG Xiaofeng MA Wentao YU Yang DONG Di LI Ziwei XU Cong State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital EarthChinese Academy of Sciences National Engineering center for geoinformatics Institute of Remote Sensing and Digital EarthChinese Academy of Sciences

Reflected signals from global navigation satellite systems（GNSSs） have been widely acknowledged as an important remote sensing tool for retrieving sea surface wind *** power of GNSS reflectometry（GNSS-R）signals can be mapped in delay chips and Doppler frequency space to generate delay Doppler power maps（DDMs）,whose characteristics are related to sea surface roughness and can be used to retrieve wind ***,the bistatic radar cross section（BRCS）,which is strongly related to the sea surface roughness,is extensively used in ***,a bistatic radar cross section（BRCS） map with a modified BRCS equation in a GNSS-R application is *** the BRCS map,three observables are proposed to represent the sea surface roughness to establish a relationship with the sea surface wind *** Hurricane Dennis（2005） GNSS-R data are then *** than 16 000 BRCS maps are generated to establish GMFs of the three ***,the proposed model and classic one-dimensional delay waveform（DW） matching methods are compared,and the proposed model demonstrates a better performance for the high wind speed retrievals.

关键词： global navigation satellite system-reflectometry Hurricane Dennis delay doppler maps bistatic radar cross section map sea surface wind speed

New spatial dimensions of global cityscapes: From reviewing existing concepts to a conceptual spatial approach

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Journal of Geographical Sciences 2016年第3期26卷 355-380页

作者： GEORG Isabel BLASCHKE Thomas TAUBENB?CK Hannes Department of geoinformatics University of Salzburg Earth Observation center (EOC) Remote Sensing Data Center (DFD)German Aerospace Center (DLR)

Current global urbanisation processes are leading to new forms of massive urban constellations. The conceptualisations and classifications of these, however, are often ambiguous, overlap or lag behind in scientific literature. This article examines whether there is a common denominator to define and delimitate–and ultimately map–these new dimensions of cityscapes. In an extensive literature review we analysed and juxtaposed some of the most common concepts such as megacity, megaregion or megalopolis. We observed that many concepts are abstract or unspecific, and for those concepts for which physical parameters exist, the parameters are neither properly defined nor used in standardised ways. While understandably concepts originate from various disciplines, the authors identify a need for more precise definition and use of parameters. We conclude that often, spatial patterns of large urban areas resemble each other considerably but the definitions vary so widely that these differences may surpass any inconsistencies in the spatial delimitation process. In other words, today we have tools such as earth observation data and Geographic Information Systems to parameterise if clear definitions are provided. This appears not to be the case. The limiting factor when delineating large urban areas seems to be a commonly agreed ontology.

关键词： urban concepts large urban areas conceptualization urbanization megacity metropolis ribbon development urban sprawl conurbation city region agglomeration megaregion urban corridor

Graphics processing unit-based dynamic volume rendering for typhoons on a virtual globe

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International Journal of Digital Earth 2015年第6期8卷 431-450页

作者： Po Liu Jianhua Gong Miao Yu State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijingChina University of Chinese Academy of Sciences BeijingChina Zhejiang-CAS Application center for geoinformatics ZhejiangChina

Typhoons are usually accompanied by strong winds,heavy rain,storm surges and other disastrous events,and they are the most severe weather phenomena in the western part of the North Pacific *** is a key technology for analysing and presenting climate simulations and observations together with related social and ecological *** globes are a logical platform for visualising such geospatial data via the *** implement interactive visualisation of typhoon data within virtual globes,this study provides a 3D texture-mapping algorithm to render volume textures on a *** addition,a systematic framework is proposed in which a hierarchical octree-based multiresolution data structure is implemented to organise the large volume dataset,and a graphics processing unit-based dynamic interpolation approach is proposed to obtain a smooth ***,the structure is combined with a level of detail strategy to enable the rendering of dynamic volumetric data at an acceptable interactive frame *** demonstrate the capabilities of this framework,data for a simulated typhoon event were rendered in World Wind,an open-source virtual *** experimental results demonstrate that the application of the proposed strategies can result in an interactive visualisation performance that renders typhoon data on virtual globes.

关键词： typhoon GPU volume animation octree LOD virtual globes

A monocular visual SLAM system augmented by lightweight deep local feature extractor using in-house and low-cost LIDAR-camera integrated device

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International Journal of Digital Earth 2022年第1期15卷 1929-1946页

作者： Jing Li Chenhui Shi Jun Chen Ruisheng Wang Zhiyuan Yang Fan Zhang Jianhua Gong National Engineering Research center for geoinformatics Aerospace Information Research InstituteChinese Academy of SciencesBeijingPeople’s Republic of China National Geomatics center of China BeijingPeople’s Republic of China Department of Geomatics Engineering University of CalgaryCalgaryCanada Department of Urban Studies and Planning Massachusetts Institute of TechnologyCambridgeMAUSA

Simultaneous Localization and Mapping(SLAM)has been widely used in emergency response,self-driving and city-scale 3D mapping and *** deep-learning based feature point extractors have demonstrated superior performance in dealing with the complex environmental challenges(*** lighting)while the traditional extractors are *** this paper,we have successfully improved the robustness and accuracy of a monocular visual SLAM system under various complex scenes by adding a deep learning based visual localization thread as an augmentation to the visual SLAM *** this thread,our feature extractor with an efficient lightweight deep neural network is used for absolute pose and scale estimation in real time using the highly accurate georeferenced prior map database at 20cm geometric accuracy created by our in-house and low-cost LiDAR and camera integrated *** closed-loop error provided by our SLAM system with and without this enhancement is 1.03m and 18.28m *** scale estimation of the monocular visual SLAM is also significantly improved(0.01 versus 0.98).In addition,a novel camera-LiDAR calibration workflow is also provided for large-scale 3D *** paper demonstrates the application and research potential of deep-learning based vision SLAM with image and LiDAR sensors.

关键词： Deep local features lightweight network visual localization SLAM LiDAR

Medical transportation and the contribution of air medical evacuation in isolated mountainous areas of Greece-Case study,Municipality of Agrafa

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Journal of Mountain Science 2022年第11期19卷 3178-3191页

作者： Ioanna KARANI Anastasios BALASKAS Dimitris KALIAMPAKOS School of Rural Surveying and Geoinformatics EngineeringNational Technical University of AthensAthens 15780Greece School of Mining and Metallurgical Engineering National Technical University of AthensAthens 15780Greece Metsovion Interdisciplinary Research center National Technical University of AthensAthens 15780Greece

In every emergency medical situation,access to emergency medical services is an inalienable right of any *** average acceptable time to provide first aid assistance is 60 *** this paper,the possibility of using helicopters for air travel in mountainous areas was examined for the first time for all of Greece and especially for a mountainous and isolated area such as the Municipality of ***,the time distance-virtual distance,from the hospitals was calculated at the national level of Greece,with an acceptable first contact time of 60 minutes(golden hour),i.e.,less than two hours from the nearest hospital to the incident and back to the hospital and the relevant conclusions are ***,the case study of Municipality of Agrafa,one of the most mountainous areas in Greece,was *** time distance of the settlements from the nearest primary health point,namely the Primary Health Centre(PHC)of West Fragkista,was calculated and the transportation by ground means was compared with the corresponding time by flying means,to investigate the contribution of air transportation or not,of the timely arrival of the patients in the appropriate health ***,possible helicopter landing locations were identified,using a geographic information system to facilitate the process of air medical transportation in the Municipality of Agrafa.

关键词： Civil air transport Mountain areas Landing sites Travel time Greece