Access to the EGNOS signal in space over mobile-IP

The EGNOS service will provide better positioning availability and accuracy than that from the standalone GPS solutions. However, in order to access the EGNOS service, the end user needs to access the corresponding GEO satellites that broadcast the augmentation information for the region. This is not a problem normally for aviation and maritime applications because an open sky is always available for such applications. However, an open sky is not always available for land applications because of the obstacles in the vicinity of the end users, for example, in the city canyons. The situation gets worse for the regions at high latitudes because the elevation angles to the GEO satellites are rather low (e.g. 4–22° in Finland). This article describes briefly the SISNeT technology, designed and developed by the European Space Agency, which allows accessing the EGNOS SIS via the Internet. It will describe in detail the handheld SISNeT receiver, designed and developed by the Finnish Geodetic Institute under ESA contract. The SISNeT data server is an IP-based server that acquires the EGNOS messages from an EGNOS receiver, and broadcasts them over the Internet in real-time. The handheld receiver consists of a GPS PC-card receiver, a GPRS (or GSM) card phone, and a pocket PC as the host platform. The receiver software is a Windows CE-based package with a multi-process and multi-thread architecture. It simultaneously receives: (1) the EGNOS SIS over a GPRS wireless connection and the Internet and (2) the NMEA messages from a serial connection to a GPS receiver. It decompresses and decodes the EGNOS messages, and utilizes the information in the messages to estimate the EGNOS-corrected coordinates, which are finally delivered to the end user via a virtual COM port. The virtual COM port has been implemented as a stream interface driver in the Pocket PC. It can be accessed in the same way as the physical COM port in a GPS receiver is accessed. Therefore, it is easy to interface to any third-party applications. The test results show that the handheld SISNeT receiver can provide a positioning accuracy of about 1–2 m for the horizontal components, and 2–3 m for the vertical component in real time. Due to the poor performance of the wireless connection, 10–30% of the EGNOS messages can be lost depending on the services provided by the wireless network operators. The impact of the messages lost on the positioning accuracy is about 0.5 m in both the horizontal and vertical components. Electronic Publication     

Determining the road traffic accident hotspots using GIS-based temporal-spatial statistical analytic techniques in Hanoi,Vietnam

ABSTRACT

This study applied GIS-based statistical analytic techniques to investigate the influence of accident Severity Index (SI) on temporal-spatial patterns of accident hotspots related to the specific time intervals of day and seasons. Road Traffic Accident (RTA) data in 3 years (2015 ? 2017) in Hanoi, Vietnam were used to analyze and test this approach. Firstly, the RTA data were divided into four seasons in accordance with Hanoi’s weather conditions and the time intervals such as the daytime, nighttime, or peak hours. Then, the Kernel Density Estimation (KDE) method was applied to analyze hotspots according to the time intervals and seasons. Finally, the results were presented by using the comap technique. This study considered both analyses with and without SI. The accident SI measures the seriousness of an accident. The approach method is to give higher weights to the more serious accidents, but not with the extremely high values calculated on a direct rate to the accident expenditures. The results showed that both analyses determined the relatively similar hotspots, but the rankings of some hotspots were quite different due to the integration of SI. It is better to take into account SI in determining RTA hotspots because the gained results are more precise and the rankings of hotspots are more accurate. From there, the traffic authorities can easily understand the causes behind each accident and provide reasonable solutions to solve the most dangerous hotspots in case of limited budget and resources appropriately. This is also the first study about this issue in Vietnam, so the contribution of the article will help the traffic authorities easily solve this problem not only in Hanoi but also in other cities.     

基于对偶拓扑结构的路网路段重要性评估方法

现有的路网路段重要性评估方法考虑的是路网中的路段的统计特性或路网的局部结构对重要性的影响。在路段的重要性与路网的全体路段相关联的基础上,提出m阶邻居节点的复杂路网路段重要度评估方法。为验证算法的有效性,实验仿真采用成都市路网的对偶拓扑结构,在1 484个路段中提取10条关键路径对评估方法进行验证。评估结果显示:与度值法、介数法相比,该方法能显著地区分复杂路网中路段之间的重要性差异,准确地确定网络中的关键路径,具有更高的评估准确性。     

UAVDP技术在道路工程应用中的可行性研究

本文介绍了UAVDP(无人飞行器低空数字摄影测量系统)技术和配套系统的开发应用,以及UAVDP技术和配套软件在工程中应用的关键技术,简要介绍了其成果精度的评定。并讨论了该技术在公路勘测中的应用以及适合公路数字化设计的可能性。     

Modeling the traffic disruption caused by pluvial flash flood on intra‐urban road network

Pluvial flash flood (PFF) can cause serious traffic disruption in big cities. We conducted interdisciplinary research by integrating flood modeling and traffic analysis to reveal the spatiotemporal pattern of the interplay between these two processes. A simplified simulation tool, which is capable of building a road network model, assigning trip paths with the effect of road closures, and evaluating travel delay and vehicle volume redistribution in a given PFF scenario, was developed to capture the traffic disruption in the face of PFF events. Modeling outputs from a case study in the city center of Shanghai showed that the delay of vehicles diverted to dry links or trapped in flooded links may reach 0.5 to 8 times the travel time in no‐flood scenarios. Overall, approximately 1–7% of vehicle volumes on flooded links would be redistributed onto dry links (more likely major arterial roads). However, the vehicle volume variation during each time interval demonstrated evident disparity with the spatiotemporal change of flood inundations. Simulating and mapping the congestion can largely facilitate the identification of vulnerable links. Future research will test the method in other intra‐urban areas and try to bridge the gap between modeling outputs and smart city planning and management.     

线性参考系统技术在道路资产管理系统中的应用研究

分析了传统道路资产管理系统中存在的一些问题,阐述了引入线性参考系统的必要性。以线性参考系统和动态分段技术为基础,研究了道路资产管理系统的数据组织,讨论了系统实现的核心技术,主要包括道路资产评估方法和道路资产维护方案决策支持技术等。     

基于几何规则的车载近景立体影像道路交通标线自动提取

道路交通标线信息是道路导航地图中必不可少的数据,对于制作精度更高、道路细节信息更加丰富清晰的高精度导航地图具有重要的作用。本文以车载近景立体影像中的道路交通标线信息自动提取为研究目标,针对道路交通标线快速、精确采集的应用需求,提出了基于几何规则的车载近景立体影像道路交通标线自动提取方法。该方法首先分析了道路交通标线的几何特征;其次,构建了基于几何特征的交通标线信息提取规则;最后,以标线种子点为基础,结合前述规则,实现了道路交通标线三维空间信息的自动采集。以南京师范大学的车载移动测量系统拍摄的实际近景立体影像为数据进行了试验,试验结果证明,本文方法相比传统人机交互采集方法,在交通标线特征点采集效率、标线几何相似度等方面有较大的优势,可为高精度导航地图的生产提供一种可借鉴的技术支撑。     

基于路网拓扑结构的指路标志标识系统数据模型的研究与应用

针对指路标志的标识功能,分析了指路标志的特征,提出了指路标志项的概念。基于路网拓扑结构,构建了以指路标志项为基本单元的指路标志标识系统的数据模型,使得在计算机中建立指路标志的信息管理及自动设计分析应用系统成为可能。最后,在此数据模型的基础上,开发了一个基于GIS平台的指路标志标识计算机应用系统。该系统能对指路标志进行自动设计、根据交通规则的修改对指路标志执行自动更新,说明本文提出的数据模型是有效可行的。     

ComGIS在城市公共交通查询系统中的应用研究

从系统建立的必要性出发,阐述ComGIS在城市公共交通查询系统中的应用,探讨如何运用ESRI公司的GIS组件-MO与高级程序语言VC#相结合,以SQL Server 2000作为后台数据库,进行城市公共交通查询系统的开发。实现系统的基本通用功能,以及站点查询、公共交通线路查询、公共交通换乘方案和最短路径查询等空间分析功能,为广大市民及外地游客的出行提供便利。     

道路定线技术在北京市规划道路数据管理系统建设中的应用

为缩短规划道路数据的更新周期,提高数据质量,实现数据共享,设计开发了北京市规划道路数据管理系统.研究了规划道路中线条件编号表的设计以及规划道路中线点属性表中曲线标识、曲线位置、非正常曲线标识设置情况;实现了曲线元素计算、派生红线图形编辑和规划道路中线图形输出.系统通过了专家鉴定,并被北京市测绘设计研究院等多家单位使用,实际应用证明,本系统设计合理,达到了预期目的,产生了良好的社会经济效益.     

测量数据处理的网络化模式

测量数据处理软件的应用使测绘工作者摆脱了手工处理测量数据的麻烦,提高了工作效率。随着单机版测绘数据处理软件的发展、成熟,设计和研发基于网络的测量数据处理系统已成为测量数据自动化处理研究领域的热点。本文利用Silverlight富客户端技术设计并实现了测量数据网络处理系统,该系统不仅具备单机平差软件丰富的测量数据处理功能,而且通过Silverlight技术改进了传统Web系统响应速度慢、页面简单、交互性差等缺点。所研发的系统具有丰富的浏览器表现,支持大量用户的并发访问,并能高效地完成用户交互。     

磁浮交通试验线压力管道直线度的测量方法研究及应用

目前,国内外对于磁浮交通真空压力管道直线度测量问题的研究较少。本文结合西南交通大学在建的真空磁浮高速列车试验装置,提出了一种真空压力管道直线度测量方法。该方法在管道内建立高精度=维控制网,依据三维控制网测量采用圆曲线拟合方法确定各节管道的圆心坐标,并采用直线拟合方法分析整个管道的直线度。最后依据上述方法编制程序对实测数据进行了处理分析,验证了方法的可行性和正确性,可为今后真空磁浮压力管道的建设提供技术参考。     

Estimation of geometric route distance from its topological distance: application to narrow road networks in Tokyo

The structure of road networks has been investigated in accordance with the development of GIScience. By classifying road networks into wide and narrow ones, we can define the route as the path from the route’s origin (also called the root) on a wide road network to a narrow road segment which consists of the sequence of narrow road segments arranged by ascending order of the number of steps of adjacency to its root. The length of the route can be defined with the following geometric and topological terms: the route distance, measuring the length along the route and the depth, counting the number of road segments on the route. The depth plays the important role of being a substitute for the route distance in modelling road networks as a planar graph. Since road networks clearly exhibit irregular patterns and road segment lengths are non-uniform, it is considered appropriate to adopt a stochastic approach rather than a deterministic one to analyse the route distance. However, the relationship between the route distance and its depth has not been sufficiently investigated stochastically. Therefore, the research question is how can we estimate the route distance from its depth? Based on an empirical study in the Tokyo metropolitan region, it was found that (1) the statistical distribution of the route distance can be formulated as an Erlang distribution whose parameters are its depth and the inverse of the mean length of narrow road segments, and (2) this length is constant and close to 40 m. Therefore, we can estimate the route distance from only one parameter, the depth. Also, as a practical application, accessibility to the kth depth link in terms of firefighting was evaluated because the maximum length of the extension of fire hoses is approximately 200 m. It was found that (1) even if k?≤?5, the probability that the route distance to the kth depth link is equal to or longer than 200 m ranges from 0 to 0.45; and (2) if k?≥?8, the probability is approximately 1. These indicate the limitation of the deterministic approach because, on the basis of complete grid patterns (with intervals of 40 m between intersections), k?=?5 corresponds to a distance of 200 m from wide road networks and the route to the 5th depth link can be covered with fire hoses. Moreover, it was found that the connectivity of wide road networks is higher than that of narrow ones in terms of the smaller ratio of cul-de-sacs and the larger ratio of four-way intersections. These answers contribute substantially not only to constructing a science of cities that provides a simple model and specifies the most important parameter, but also to our understanding of the structure of narrow road networks within several hundred metres of wide road networks.     

顾及道路等级的几何信息量量测方法

几何信息量量测是地理信息量量测最重要的方面之一。本文在分析比较了常规几何信息量量测方法的基础上,从道路的等级信息出发,提出一种顾及道路等级信息的几何信息量测思想,并用加权熵和密度图等方法实现,实验证明这种顾及道路等级的几何信息量测能较准确反映道路的分布规律和不同等级的要素造成的信息量差别。     

训练模拟系统中地形量化模型的探讨

现代作战模拟系统大多保留"对弈"的推演思路,每一步推演在空间上并非连续,而是按照一定的空间间距和时间间距进行计算的,类似于在网格状的棋盘上下棋.这种网格结构及其属性就是地形量化模型,它是决定地形分辨率及推演实时计算的关键因素之一.重点探讨了地形量化模型的概念、特点及建模流程等方面的内容,为针对不同训练模拟系统的具体需求选择适当的地形量化模型提供了有益的参考.     

训练模拟系统中地形量化模型的探讨

现代作战模拟系统大多保留对弈的推演思路,每一步推演在空间上并非连续,而是按照一定的空间间距和时间间距进行计算的,类似于在网格状的棋盘上下棋。这种网格结构及其属性就是地形量化模型,它是决定地形分辨率及推演实时计算的关键因素之一。重点探讨了地形量化模型的概念、特点及建模流程等方面的内容,为针对不同训练模拟系统的具体需求选择适当的地形量化模型提供了有益的参考。     

反向灰色模型的初值优化在道路沉降中应用

针对灰色GM(1,1)模型预测单调递减数据会出现不合理计算误差的问题,建立反向灰色GOM(1,1)模型,利用遗传算法改进x(1)(n)的初始值范围,求出最佳初始值x替换x(0)(1)作为模型初始条件。通过选取高速公路地面沉降数据进行实例计算,证实优化后模型的有效性。     

地质雷达+三维测量内窥镜的城市道路病害检测与应用

城市道路病害体作为城市安全的重要隐患,具有隐蔽性、突发性等特点,需及时予以检测和处理。地质雷达利用电磁波反射确定地下介质分布,以其无损、快捷及浅层高分辨率优势广泛应用于城市道路病害检测中,但要对病害体作进一步处理,需要对病害体做进一步精细勘测。本文利用地质雷达在道路病害检测中的优势,结合三维测量内窥镜技术的实时视频和测量功能,实现道路地下病害体的准确定位和精准测量,为后续防治和治理提供有用数据。     

图卷积网络在道路网选取中的应用

针对现有制图综合中的道路网自动选取方法不能有效地利用道路网的空间特征问题,该文把道路网抽象为图结构,提出了使用图卷积网络来进行道路网的自动选取,并比较分析了不同的图卷积网络在道路网选取中的适用性。结果表明,图卷积网络可以通过多层卷积来自动提取不同局部范围的空间特征,从而减少空间特征的人工构建,相比传统的多层感知机(MLP)等人工智能选取方法,具有更高的选取精度。对于不同的图卷积网络模型,使用最大池化聚合的GraphSAGE获得了最优的性能。     

道路勘测阶段控制测量方法的研究

道路勘测控制测量作为线路施工放样的依据,必须建立具备一定精度的控制网,测量仪器及施工方法对工程质量将会产生很大影响。结合张承高速公路二期工程所处测区概况,并结合现代测量工具,从而提出该路段控制测量的最佳施测方法;通过对实测数据进行处理及分析,验证该方法的可行性。