一种VGI矢量数据增量变化发现的多层次蔓延匹配算法

目的 矢量要素的匹配是发现地物要素变化的重要方法之一,高精度的匹配结果有助于更快地发现变化地物,进行更新。VGI矢量数据具有几何和语义信息丰富的特点,但使用传统的矢量要素匹配算法难以发挥VGI矢量数据的优势。以城市 VGI道路数据为研究内容,提出基于多层次蔓延的矢量要素匹配算法,将 VGI数据和专业测绘数据进行匹配对比,从而实现道路变化增量信息的快速识别。     

面向道路网VGI数据的匹配与融合方法

自发地理信息(VGI)是一种新兴的地理数据采集方式,具有数据更新快、细节丰富、覆盖范围广等优势。利用VGI数据可以对道路网实现快速更新;但是由于VGI数据是非专业自发共享的,且数据采集时多使用非专业设备,所以存在数据质量不高的问题。大量VGI数据对同一地理要素的重复采集与融合处理则可改善数据的质量,文中以多人采集的道路网数据为例,结合矢量要素的匹配与融合理论,设计一种适用于道路网VGI数据的匹配与融合算法。首先在路段结点处建立缓冲区进行结点匹配,再根据路段距离相似度进行路段匹配,最后再利用Delaunay三角剖分融合算法对匹配后的同名路段进行融合。将匹配融合后的道路网与原始道路网VGI数据及Google影像图叠加对比分析,结果表明利用本文算法可有效地实现道路网VGI数据的匹配与融合。     

径向基函数神经网络的路网自动匹配算法

针对VGI数据中检测更新的问题,该文提出基于径向基函数的神经网络自动匹配算法。通过选取路段的距离、方向、形状和长度4个空间特征的相似度作为衡量路段是否匹配的指标。考虑到4个空间特征指标对匹配的影响力不同,在RBF(radial basis function)神经网络中的隐含层对基函数引入粒度拉伸因子,使径向对称的RBF顾及各向异性。同时对输出层在线性加权求和函数的基础上引入sigmoid函数,使计算结果(路段的匹配度值)归一化。该算法对数据质量较差的VGI路网具有很好的匹配能力,与BP神经网络相比,RBF神经网络在地图匹配中具有更好的匹配效率。     

VGI数据与地形图数据的自动融合研究

随着科学技术的不断发展,志愿者地理信息（volunteered geographic information,VGI）已经成为地理空间数据中最为重要的来源之一。为了充分利用志愿者地理信息,需要进行VGI与传统地形图数据的匹配与融合。开发了一种全新的数据自动匹配与融合算法,其目的是将ATKIS道路网数据（由德国联邦测绘局所采集的官方数据）与AOSD数据（由大量志愿者携带定位仪器进行户外徒步或骑行所获取的轨迹数据）匹配并融合起来,从而丰富传统地理信息数据的内容,并实现数据的增值。考虑到ATKIS数据与AOSD数据在空间表达上的差异很大,所开发的算法包括了道路要素的智能化分割、道路要素匹配、道路网数据融合以及融合后道路网内部要素间的匹配运算与数据集成等4个过程。大量实地数据的测试结果表明,该算法具有匹配成功率高、准确率高、运算速度快等优点。     

Assessing Data Completeness of VGI through an Automated Matching Procedure for Linear Data

New, free and fast growing spatial data sources have appeared online, based on Volunteered Geographic Information (VGI). OpenStreetMap (OSM) is one of the most representative projects of this trend. Its increasing popularity and density makes the study of its data quality an imperative. A common approach is to compare OSM with a reference dataset. In such cases, data matching is necessary for the comparison to be meaningful, and is usually performed manually at the data preparation stage. This article proposes an automated feature‐based matching method specifically designed for VGI, based on a multi‐stage approach that combines geometric and attribute constraints. It is applied to the OSM dataset using the official data from Ordnance Survey as the reference dataset. The results are then used to evaluate data completeness of OSM in several case studies in the UK.     

面向众源开放街道地图空间数据的质量评价方法

为了解决来自非专业用户协同编辑的众源地理空间数据质量问题,提出了一种众源地理空间数据质量评价技术框架。针对众源开放街道地图(open street map,OSM)数据特点,选取数据完整性、属性信息准确性和定位精度三方面质量要素,提出了面向众源开放街道地图(OSM)空间数据的质量模型和计算方法。     

OpenStreetMap data quality enrichment through awareness raising and collective action tools—experiences from a European project

ABSTRACT

Nowadays, several research projects show interest in employing volunteered geographic information (VGI) to improve their systems through using up-to-date and detailed data. The European project CAP4Access is one of the successful examples of such international-wide research projects that aims to improve the accessibility of people with restricted mobility using crowdsourced data. In this project, OpenStreetMap (OSM) is used to extend OpenRouteService, a well-known routing platform. However, a basic challenge that this project tackled was the incompleteness of OSM data with regards to certain information that is required for wheelchair accessibility (e.g. sidewalk information, kerb data, etc.). In this article, we present the results of initial assessment of sidewalk data in OSM at the beginning of the project as well as our approach in awareness raising and using tools for tagging accessibility data into OSM database for enriching the sidewalk data completeness. Several experiments have been carried out in different European cities, and discussion on the results of the experiments as well as the lessons learned are provided. The lessons learned provide recommendations that help in organizing better mapping party events in the future. We conclude by reporting on how and to what extent the OSM sidewalk data completeness in these study areas have benefited from the mapping parties by the end of the project.     

Towards an Automated Comparison of OpenStreetMap with Authoritative Road Datasets

OpenStreetMap (OSM) is an extraordinarily large and diverse spatial database of the world. Road networks are amongst the most frequently occurring spatial content within the OSM database. These road network representations are usable in many applications. However the quality of these representations can vary between locations. Comparing OSM road networks with authoritative road datasets for a given area or region is an important task in assessing OSM's fitness for use for applications like routing and navigation. Such comparisons can be technically challenging and no software implementation exists which facilitates them easily and automatically. In this article we develop and propose a flexible methodology for comparing the geometry of OSM road network data with other road datasets. Quantitative measures for the completeness and spatial accuracy of OSM are computed, including the compatibility of OSM road data with other map databases. Our methodology provides users with significant flexibility in how they can adjust the parameterization to suit their needs. This software implementation is exclusively built on open source software and a significant degree of automation is provided for these comparisons. This software can subsequently be extended and adapted for comparison between OSM and other external road datasets.     

基于影像匹配的自发地理信息道路精度评价与改善

针对无矢量参考数据自发地理信息道路精度难以评价的问题,提出了一种基于影像匹配的道路精度评价方法。首先提取影像与自发地理信息中的道路交叉口作为控制点,并将对应的交叉口进行匹配,以同名控制点的均方根误差作为自发地理信息的道路精度;然后以两组控制点分别构建Delaunay三角网,利用两组控制点的对应关系对每个三角网进行仿射变换,从而实现对自发地理信息道路的几何纠正,以提高其精度。最后以郑州市的Open Street Map道路数据进行试验,结果表明本文算法能够有效提高自发地理信息的道路精度。     

Geometric quality assessment of trajectory‐generated VGI road networks based on the symmetric arc similarity

As large amounts of trajectories from a wide variety of Volunteered Geographic Information (referred to as VGI) contributors pour into the spatial database, the geometric qualities of the VGI road networks generated from these trajectories are different from the ground truth road dataset and so need to be differently assessed. To address this issue, an assessment approach based on symmetric arc similarity is proposed, and the geometric quality of a VGI road network is assessed by its conformity with the corresponding ground truth road network, the results being visualized as hierarchical thematic maps. To compute the conformity, the geometric similarity between the VGI road arc and the corresponding ground truth road arc, which is selected by the adaptive searching distance, is measured based on the symmetric arc similarity method; the geometric quality is assessed based on an assessment matrix. Also, the symmetric arc similarity method is independent of directions and with a feature of shift‐independence, which is applicable to assess the geometric qualities of different VGI road networks and makes the assessment result consistent with the actual situation of the real world. The robustness and scalability of the approach are examined using VGI road networks from different sources.     

Modeling aggregated expertise of user contributions to assess the credibility of OpenStreetMap features

The emergence of volunteered geographic information (VGI) during the past decade has fueled a wide range of research and applications. The assessment of VGI quality and fitness‐of‐use is still a challenge because of the non‐standardized and crowdsourced data collection process, as well as the unknown skill and motivation of the contributors. However, the frequent approach of assessing VGI quality against external data sources using ISO quality standard measures is problematic because of a frequent lack of available external (reference) data, and because for certain types of features, VGI might be more up‐to‐date than the reference data. Therefore, a VGI‐intrinsic measure of quality is highly desirable. This study proposes such an intrinsic measure of quality by developing the concept of aggregated expertise based on the characteristics of a feature's contributors. The article further operationalizes this concept and examines its feasibility through a case study using OpenStreetMap (OSM). The comparison of model OSM feature quality with information from a field survey demonstrates the successful implementation of this novel approach.     

Analyzing the effect of earthquakes on OpenStreetMap contribution patterns and tweeting activities

ABSTRACT

Natural disasters, such as wildfires, earthquakes, landslides, or floods, lead to an increase in topical information shared on social media and in increased mapping activities in volunteered geographic information (VGI) platforms. Using earthquakes in Nepal and Central Italy as case studies, this research analyzes the effects of natural disasters on short-term (weeks) and longer-term (half year) changes in OpenStreetMap (OSM) mapping behavior and tweet activities in the affected regions. An increase of activities in OSM during the events can be partially attributed to those focused OSM mapping campaigns, for example, through the Humanitarian OSM Team (HOT). Using source tags in OSM change-sets, it was found that only a small portion of external mappers actually travels to the affected regions, whereas the majority of external mappers relies on desktop mapping instead. Furthermore, the study analyzes the spatio-temporal sequence of posted tweets together with keyword filters to identify a subset of users who most likely traveled to the affected regions for support and rescue operations. It also explores where, geographically, earthquake information spreads within social networks.     

多尺度道路网的距离匹配算法研究

根据道路网折线的匹配特点,提出基于格网索引的折线——结点距离匹配算法,将复杂的折线与折线之间的几何相似度计算转换为求结点到折线距离的匹配方法,降低了计算复杂度,并通过建立格网索引来提高计算效率。在应用实例中,采用曲线拟合的最小二乘法确定算法的匹配容差和匹配成功率之间的关系,并通过与现有统计匹配算法比较,可知该算法效率高且匹配成功率较理想,能够满足多尺度道路网数据匹配的应用需求。     

一种路网拓扑约束下的增量型地图匹配算法

着眼于低频浮动车轨迹数据,对地图匹配问题进行了抽象,并分析了影响匹配结果的几何约束与拓扑约束。针对GPS采样的低频性和城市路网的复杂性,提出了一种路网拓扑约束下的增量型地图匹配算法（topology-constrained incremental matching algorithm,TIM）。选取北京市浮动车的GPS样例轨迹数据进行匹配,结果表明,该匹配算法在不同复杂程度的城市路网下均表现较好。     

一种改进的快速浮动车地图匹配方法

浮动车地图匹配算法能够实现浮动车离散点与路段的快速准确匹配,是浮动车路况信息生成技术中的核心环节。本文针对现有方法的不足,实现了建立定位点的有效阈值缓冲区,并依据空间关系检索候选匹配路段,研究实现了一种利用行驶速度、行驶方向、投影距离、行驶距离4个参数进行行车轨迹判别的逻辑匹配算法。试验表明,该方法无需对路网数据进行大量的前期处理工作,简化了候选匹配路段的检索过程,在保证匹配正确率的同时也表现出了更高的效率。     

Completeness of citizen science biodiversity data from a volunteered geographic information perspective

Observations of living organisms by citizen scientists that are reported to online portals are a valuable source of information. They are also a special kind of volunteered geographic information (VGI). VGI data have issues of completeness, which arise from biases caused by the opportunistic nature of the data collection process. We examined the completeness of bird species represented in citizen science observation data from eBird and iNaturalist in US National Parks (NPs). We used approaches for completeness estimation which were developed for data from OpenStreetMap, a crowdsourced map of the world. First, we used an extrinsic approach, comparing species lists from citizen science data with National Park Service lists. Second, we examined two intrinsic approaches using total observation numbers in NPs and the development of the number of new species being added to the data-set over time. Results from the extrinsic approach provided appropriate completeness estimations to evaluate the intrinsic approaches. We found that total observation numbers are a good estimator of species completeness of citizen science data from US NPs. There is also a close relationship between species completeness and the ratio of new species added to observation data vs. observation numbers in a given year.     

浅论自发地理信息的数据管理

自发地理信息（volunteered geographic information,VGI）由大众志愿者自发标报,导致其可信度具有诸多不确定性,但目前的研究工作很少考虑用户信誉对于VGI质量的影响,因此提出基于用户信誉的VGI可信度计算模型。首先提出了VGI的用户信誉模型,模型综合考虑了用户的初始信誉和评价信誉两方面,在此基础上综合地理要素的编辑过程和贡献者的信誉等因素发展了地理对象的可信度计算模型。最后采用OpenStreetMap的真实历史数据中的线对象进行实验,实验结果表明,线要素的质量和可信度值呈正相关关系。本文从可信度的角度来评价自发地理信息,为VGI的质量评价和筛选提供了新的视角。     

An assessment of a collaborative mapping approach for exploring land use patterns for several European metropolises

Until recently, land surveys and digital interpretation of remotely sensed imagery have been used to generate land use inventories. These techniques however, are often cumbersome and costly, allocating large amounts of technical and temporal costs. The technological advances of web 2.0 have brought a wide array of technological achievements, stimulating the participatory role in collaborative and crowd sourced mapping products. This has been fostered by GPS-enabled devices, and accessible tools that enable visual interpretation of high resolution satellite images/air photos provided in collaborative mapping projects. Such technologies offer an integrative approach to geography by means of promoting public participation and allowing accurate assessment and classification of land use as well as geographical features. OpenStreetMap (OSM) has supported the evolution of such techniques, contributing to the existence of a large inventory of spatial land use information. This paper explores the introduction of this novel participatory phenomenon for land use classification in Europe's metropolitan regions. We adopt a positivistic approach to assess comparatively the accuracy of these contributions of OSM for land use classifications in seven large European metropolitan regions. Thematic accuracy and degree of completeness of OSM data was compared to available Global Monitoring for Environment and Security Urban Atlas (GMESUA) datasets for the chosen metropolises. We further extend our findings of land use within a novel framework for geography, justifying that volunteered geographic information (VGI) sources are of great benefit for land use mapping depending on location and degree of VGI dynamism and offer a great alternative to traditional mapping techniques for metropolitan regions throughout Europe. Evaluation of several land use types at the local level suggests that a number of OSM classes (such as anthropogenic land use, agricultural and some natural environment classes) are viable alternatives for land use classification. These classes are highly accurate and can be integrated into planning decisions for stakeholders and policymakers.