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行程时间不确定性导致了可达性随时间的变化,相关研究表明忽略行程时间不确定性会高估可达性水平。既有可达性研究往往用行程时间可靠性表示行程时间不确定性,但未考虑不同可达性模型结果的差异以及行程时间可靠性价值。本文结合各OD之间的行程时间分布特征,构建方差型的行程时间可靠性来描述行程时间不确定性,并进一步将行程时间可靠性纳入到广义出行时间成本中,建立了时间距离模型、潜力模型、累计机会模型和高斯模型4种基于位置的可达性测算方法,以比较在不同测算方法下,行程时间不确定性对可达性的影响。深圳的案例研究表明：(1)忽略行程时间不确定性会使全区域的可达性至少被高估5.04%,最大被高估95.04%。潜力模型、时间距离模型、累计机会模型和高斯模型的高估幅度由低到高;(2)行程时间不确定性对可达性的影响存在阈值效应,阈值越高,可达性受影响的程度越小;(3)从空间分布来看,行程时间不确定性对可达性水平高和低的区域都有一定影响。若不考虑行程时间不确定性,可达性高的区域高估值大,而在可达性低的区域,可达性高估的百分比较大,高估百分比中位数的差异程度最大可达77.1%;(4)行程时间不确定性对潜力模型可达性分类的... 相似文献
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Biodiversity maps are an important component of ecosystem-based management and conservation. In the past, biodiversity maps were largely generated using patchy occurrence data from a range of data sources. Currently, substantial species occurrence data are readily available for large parts of the world and are accessible programmatically. Considering both the observed and expected changes in species distributions, and hence biodiversity, in response to present and future climate change, it is important to utilise readily available species occurrence databases to generate temporal and spatial biodiversity maps. In this study biodiversity maps were generated for three generic functional groups within the exclusive economic zone of South Africa: zooplankton, fishes and benthos. This was achieved by stacking individual species-distribution maps. Freely available occurrence data from the Ocean Biogeographic Information System (OBIS) were accessed for this purpose. Ensemble species-distribution modelling, employing five widely used statistical methods, was used to generate species-distribution maps for each functional group. The resulting spatial patterns of biodiversity for the three functional groups were largely in agreement with known patterns. The results of this study highlight the value of open-source occurrence and environmental data to generate biodiversity maps that can potentially be used in future spatial prioritisation or planning for management of marine areas and in environmental-change studies. 相似文献
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为了更好地实现地理空间数据和信息共享,在分析Web GIS平台、开源GIS、OGC规范以及Web服务的基础上,设计与开发一个基于OGC规范的Web GIS开源服务平台,并给出具体的实现步骤。该方案可高效地完成矢量数据入库、可视化浏览、空间对象属性查询、地图编辑和空间分析等任务,能够为集成应用提供标准的数据访问和获取接口。最后,将其应用到"太湖流域雨量水情信息服务"中,取得较好的效果。 相似文献
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简要介绍了实现开源平台WebGIS的一些技术,从这些技术出发,设计并实现了一套基于开源平台Web专题地图系统。该系统易于使用,相较于基于非开源平台的实现,具有低成本,易于维护等特点。同时,进一步探讨了将开源技术引入WebGIS开发领域的优势所在。 相似文献
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Benchmark on the accuracy and efficiency of several neural network based phase pickers using datasets from China Seismic Network 
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下载免费PDF全文 Seismic phase pickers based on deep neural networks have been extensively used recently, demonstrating their advantages on both performance and efficiency. However, these pickers are trained with and applied to different data. A comprehensive benchmark based on a single dataset is therefore lacking. Here, using the recently released DiTing dataset, we analyzed performances of seven phase pickers with different network structures, the efficiencies are also evaluated using both CPU and GPU devices. Evaluations based on F1-scores reveal that the recurrent neural network (RNN) and EQTransformer exhibit the best performance, likely owing to their large receptive fields. Similar performances are observed among PhaseNet (UNet), UNet++, and the lightweight phase picking network (LPPN). However, the LPPN models are the most efficient. The RNN and EQTransformer have similar speeds, which are slower than those of the LPPN and PhaseNet. UNet++ requires the most computational effort among the pickers. As all of the pickers perform well after being trained with a large-scale dataset, users may choose the one suitable for their applications. For beginners, we provide a tutorial on training and validating the pickers using the DiTing dataset. We also provide two sets of models trained using datasets with both 50 Hz and 100 Hz sampling rates for direct application by end-users. All of our models are open-source and publicly accessible. 相似文献
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Juan Mariano Camarillo-Naranjo Natalia Limones-Rodríguez María Fernanda Pita-López Mónica Aguilar-Alba 《International Journal of Digital Earth》2019,12(4):394-414
This paper summarizes our work on building a data model and a geovisualization tool that provides access to global climate data: the Global Climate Monitor Web Viewer. Linked to this viewer, a complete set of climate-environmental indicators capable of displaying climate patterns on a global scale that is accessible to any potential user (scientists and laypeople) will be built and published using the same online application. The data currently available correspond to the CRU TS3.21 version of the Climate Research Unit (University of East Anglia) database – a product that provides data at a spatial resolution of half of a degree in latitude and longitude, spanning January 1901 to December 2012, on a monthly basis. Since January 2013, the datasets feeding the system have been the GHCN-CAMS temperature dataset and the Global Precipitation Climatology Centre (GPCC) First Guess precipitation dataset. Climatologists, hydrologists, planners and non-experts users such as media workers, policymakers, non-profit organizations, teachers or students, can access useful climatological information through the Global Climate Monitor system. 相似文献
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Michelle C. Hamilton John A. Nedza Patrick Doody Matthew E. Bates Nicole L. Bauer Demetra E. Voyadgis 《International journal of geographical information science》2016,30(8):1667-1686
The emerging ubiquity of geospatial information is providing an unprecedented opportunity to apply Geographical Information Systems (GIS)-based multiple criteria decision analysis (MCDA) to a broad spectrum of use cases. Volunteered geographic information, open GIS software, geoservice-based tools, cloud-based virtualized platforms, and worldwide collaboration of both domain experts and general users have greatly increased the quantity and accessibility of geospatially referenced data resources. Currently, there is a lack of GIS-based MCDA tools that integrate this decision-driven process within a widely accessible, robust geoframework environment, designed for user-friendly interaction. In this contribution, we present a conceptual workflow and proof-of-concept software application, Geocentric Environment for Analysis and Reasoning (GEAR), which provides a viable transition path to enhance geospatial MCDA in the age of open GIS. We propose a Web-based platform that leverages open-source geotechnologies to incorporate a wide variety of geospatial data formats in a common solution space to allow for spatially enhanced and time-relevant decision analysis. Through the proposed workflow, a user can ingest and modify heterogeneous data formats, exploit temporally tagged data sources, create multicriteria decision analysis models, and visualize the results in an iterative and collaborative workspace. A sample case study applied to disaster relief is used to demonstrate the prototype and workflow. This proof-of-concept Web-based application provides a notional pathway of how to connect open-source data to open-source analysis through a geospatially enabled MCDA workflow that could be virtually accessible to many levels of decision makers from individuals to entire organizations. 相似文献
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针对海量地形数据实时渲染,本文采用开源跨平台三维渲染引擎OSG(Open Scene Graph)技术,设计了一种海量地形快速渲染方案。文中对场景结构的组织和管理、LOD调度等关键技术展开了研究,分析了生成IVE三维模型的分页LOD层次结构,提出了一种海量地形快速渲染的实现方法。试验结果实现了海量地形数据的实时加载、距离坡度测量、多种场景漫游方式以及水淹分析等功能,对工程实践有一定的指导意义。 相似文献
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