基于位置服务的语义位置建模研究

位置是实现位置服务的基础,语义位置模型从语义的角度描述与组织位置信息,能够更好地反映位置的全部特征,因而正逐渐成为位置服务的研究热点。鉴于目前语义位置模型存在研究内容不明确、形式化表达不具体和难以实际应用的问题,本文重点剖析了语义位置的内涵,详细描述了基于本体的语义位置逻辑结构及形式化表达,并建立了基于商场的语义位置模型。     

PSD位置测量系统的实现及技术问题探讨

介绍了ＰＳＤ光电位置传感器及其测量系统的构成，并对位置测量系统中应着重考虑的技术问题进行了较深入的讨论，同时介绍了测量系统的其它应用领域。     

一种规则化自然语言位置估算方法

位置信息是位置信息服务的前提和基础,位置信息的转换对统一位置信息描述和信息之间的空间联系具有重要的意义.针对估算规则化自然语言位置的空间位置的问题,首先分析了规则化自然语言位置的特征和内涵,总结出其结构化的表达形式;然后提出了一种规则化自然语言位置估算方法.     

一步彩虹全息术的成象位置分析

本文从标量衍射理论出发,结合一定的物理意义,直接导出了一步彩虹全息术的成象位置公式;并根据可观察再现象的条件,从理论上导出了较为完整的成象位置关系表;并从中选出一部分成象位置关系进行了实验验证。     

基于星心坐标系的视位置计算

在天文计算中所用到的观测瞬间的恒星坐标，一般是从某一历元的恒星位置表中的平坐标通过视位置计算得到。但这是针对测站设在地球上进行的，对于以导航卫星为测站的恒星位置计算还没有进行具体的推导。文中通过对基于星心坐标系视位置计算原理的详细分析，给出了基于星心坐标系恒星和卫星的视位置计算方法、公式和步骤，并通过编程试算，对测站设在地面上和测站设在卫星上的视位置改正的大小进行了初步比较，验证了程序的正确性。     

室内位置信息模型与智能位置服务

商业中心、交通枢纽、医院、停车场等复杂室内及地下空间的安全管理与应急响应对室内外无缝导航与位置服务的需求日益迫切,提出了一种室内位置信息模型,扩展了OGC标准CityGML和IndoorGML中的位置信息描述,提供了描述室内相对位置和室内绝对位置的本体,介绍了一种针对三维建筑物模型的室内空间自动提取方法,为智能位置服务奠定了重要基础。     

数字化地图位置精度的统计分析

本文利用统计分析方法,结合１４５幅数字化地图,对规则地物的数字化精度进行了分析研究,得出结论：数字化图面精度一般为±０．１３ｍｍ,其最大允许误差为±０．４ｍｍ。并且,还从数字化仪、操作员、图形的难易程度等几个方面探讨了它们对数字化精度的影响规律,通过这些方法可动态跟踪产品质量,及时发现问题、解决问题。     

刊登地图的最佳位置

一天在香山上唱歌,旁边的朋友告诉了我一些电子地图的网站。我说我主要是收藏传统地图,因为它们的介质不是“比特”,看得见,摸不着。人类“发明”地图这种东西已经至少5000年了,现在我们能收到的最多200年,而电子地图出现不过10年,而且因为是网上,没有收藏障碍,而收藏历来是以稀为贵的。     

Integrated compression of vehicle spatio‐temporal trajectories under the road stroke network constraint

With fast growth of all kinds of trajectory datasets, how to effectively manage the trajectory data of moving objects has received a lot of attention. This study proposes a spatio‐temporal data integrated compression method of vehicle trajectories based on stroke paths coding compression under the road stroke network constraint. The road stroke network is first constructed according to the principle of continuous coherence in Gestalt psychology, and then two types of Huffman tree—a road strokes Huffman tree and a stroke paths Huffman tree—are built, based respectively on the importance function of road strokes and vehicle visiting frequency of stroke paths. After the vehicle trajectories are map matched to the spatial paths in the road network, the Huffman codes of the road strokes and stroke paths are used to compress the trajectory spatial paths. An opening window algorithm is used to simplify the trajectory temporal data depicted on a time–distance polyline by setting the maximum allowable speed difference as the threshold. Through analysis of the relative spatio‐temporal relationship between the preceding and latter feature tracking points, the spatio‐temporal data of the feature tracking points are all converted to binary codes together, accordingly achieving integrated compression of trajectory spatio‐temporal data. A series of comparative experiments between the proposed method and representative state‐of‐the‐art methods are carried out on a real massive taxi trajectory dataset from five aspects, and the experimental results indicate that our method has the highest compression ratio. Meanwhile, this method also has favorable performance in other aspects: compression and decompression time overhead, storage space overhead, and historical dataset training time overhead.     

一种基于道路网络模型减少车辆轨迹数据量的算法

定位及移动通信的发展使我们可以获取和传输车辆在道路网络上的轨迹信息。除实现定位或导航等基本功能外,从车辆轨迹数据中还可以提取大量的交通信息,成为交通规划和管理的一个重要的信息来源。通过建立轨迹数据与道路网络之间的拓扑关系,提取轨迹数据中能代表主要信息的特征点来代替大量的轨迹数据,以达到减少轨迹数据量的目的。特征点通过一个综合了网络关系、速度币口方向的筛选方法进行提取,该方法也同时有利于建立轨迹数据检索结构和定义查询语言,系统的实验和分析验证了所提出方法的有效性。     

出租车轨迹数据的频繁轨迹识别

为识别城市交通中的频繁路径,本文提出了一种出租车轨迹数据的频繁轨迹识别方法。该方法首先对轨迹数据进行轨迹压缩,以降低计算复杂度;然后基于最长公共子序列和动态时间规整算法进行轨迹相似性度量计算,利用计算得到的轨迹间相似度生成距离矩阵;最后将生成的距离矩阵结合HDBSCAN算法进行聚类得到频繁轨迹。选取厦门岛内两个区域进行试验分析,结果表明,该方法能够识别出轨迹数据集中的频繁轨迹,进而得到城市区域之间通行的频繁路径,对道路规划、路径优化与推荐、交通治理等应用提供帮助。     

A Chain-Code-Based Map Matching Algorithm for Wheelchair Navigation

Accurate vehicle tracking is essential for navigation systems to function correctly. Unfortunately, GPS data is still plagued with errors that frequently produce inaccurate trajectories. Research in map matching algorithms focuses on how to efficiently match GPS tracking data to the underlying road network. This article presents an innovative map matching algorithm that considers the trajectory of the data rather than merely the current position as in the typical map matching case. Instead of computing the precise angle which is traditionally used, a discrete eight-direction chain code, to represent a trend of movement, is used. Coupled with distance information, map matching decisions are made by comparing the differences between trajectories representing the road segments and GPS tracking data chain-codes. Moreover, to contrast the performance of the chain-code algorithm, two evaluation strategies, linear and non-linear, are analyzed. The presented chain-code map matching algorithm was evaluated for wheelchair navigation using university campus sidewalk data. The evaluation results indicate that the algorithm is efficient in terms of accuracy and computational time.     

路网环境下的混合数据最近邻查询算法

路网环境下的k最近邻查询方法在地理信息系统、智慧城市、数据挖掘、医疗营救和物流配送等领域都有着较为重要的作用,已有路网环境下的最近邻查询方法无法直接解决查询对象为点而数据对象为点和线段混合的复杂数据的近邻查询问题,为了弥补已有方法的不足,提出了路网环境下混合复杂数据的最近邻查询算法。将查询过程分为预处理、数据集约减和数据集精炼3个部分,并与3种对比算法进行对比实验,研究了测试数据对象的数量、路网规模的大小对中央处理器运行时间以及输入/输出代价的影响。结果表明,所提算法能有效地处理路网环境下混合数据的最近邻查询问题。     

Path-finding through flexible hierarchical road networks: An experiential approach using taxi trajectory data

Optimal paths computed by conventional path-planning algorithms are usually not “optimal” since realistic traffic information and local road network characteristics are not considered. We present a new experiential approach that computes optimal paths based on the experience of taxi drivers by mining a huge number of floating car trajectories. The approach consists of three steps. First, routes are recovered from original taxi trajectories. Second, an experiential road hierarchy is constructed using travel frequency and speed information for road segments. Third, experiential optimal paths are planned based on the experiential road hierarchy. Compared with conventional path-planning methods, the proposed method provides better experiential optimal path identification. Experiments demonstrate that the travel time is less for these experiential paths than for paths planned by conventional methods. Results obtained for a case study in the city of Wuhan, China, demonstrate that experiential optimal paths can be flexibly obtained in different time intervals, particularly during peak hours.     

高光谱影像特征选择的快速克隆选择算法(英文)

Clonal selection feature selection algorithm (CSFS) based on clonal selection algorithm (CSA), a new computational intelligence approach, has been proposed to perform the task of dimensionality reduction in high-dimensional images, and has better performance than traditional feature selection algorithms with more computational costs. In this paper, a fast clonal selection feature selection algorithm (FCSFS) for hyperspectral imagery is proposed to improve the convergence rate by using Cauchy mutation instea...     

An enhanced approach for surface flow routing over drainage‐constrained triangulated irregular networks

The accuracy and efficiency of the simulations in distributed hydrological models must depend on the proper estimation of flow directions and paths. Numerous studies have been carried out to delineate the drainage patterns based on gridded digital elevation models (DEMs). The triangulated irregular network (TIN) has been increasingly applied in hydrological applications due to the advantages of high storage efficiency and multi‐scale adaptive performance. Much of the previous literature focuses mainly on filling the depressions on gridded DEMs rather than treating the special cases in TIN structures, which has hampered its applications to hydrological models. This study proposes a triangulation‐based solution for the removal of flat areas and pits to enhance the simulation of flow routing on triangulated facet networks. Based on the drainage‐constrained TIN generated from only a gridded DEM by the compound point extraction (CPE) method, the inconsistent situations including flat triangles, V‐shape flat edges and sink nodes are respectively identified and rectified. The optimization algorithm is an iterative process of TIN reconstruction, in which the flat areas are generalized into their center points and the pits are rectified by embedding break lines. To verify the proposed algorithm and investigate the potential for flow routing, flow paths of steepest descent are derived by the vector‐based tracking algorithm based on the optimized TIN. A case study of TIN optimization and flow path tracking was performed on a real‐world DEM. The outcomes indicate that the proposed approach can effectively solve the problem of inconsistencies without a significant loss in accuracy of the terrain model.     

An improved ionosphere interpolation algorithm for network RTK in low-latitude regions

A traditional interpolation algorithm with the linear interpolation method (LIM) using a fixed number of reference stations is widely used in network RTK to obtain the ionospheric delays for the users. In low-latitude regions, where the ionosphere is relatively active, however, large interpolation errors exist, especially for satellites at low elevation angles. Considering the characteristics of “coinciding ionospheric pierce points (CIPPs)” with a similar nature of ionospheric delays, an improved interpolation algorithm is proposed. In this algorithm, all stations with CIPPs are used to establish the interpolation model; thus, more precise interpolation model is achieved. To validate the performance of the proposed algorithm, data from some reference stations in Guangdong Province of China were used, and the results are compared with those with the traditional interpolation algorithm. Numerical analysis shows that the interpolation accuracy of the proposed algorithm increases by 10–30% compared with the traditional one. Since the number of reference stations is flexible, the proposed algorithm can also balance the model accuracy with the computation burdens. In addition, the proposed algorithm is less affected by the selection of master reference station. In terms of network RTK on-the-fly positioning, the time-to-first-fix is reduced when replacing the traditional interpolation algorithm with the proposed one.     

管道内部缺陷定位的一致性检验改进算法

针对管道内部缺陷定位中,里程轮累积误差较大的问题,提出了一种改进的一致性检验算法。在原有一致性检验的基础上,新定义了一种置信距离测度,消除了不同测量精度里程轮之间存在两种置信距离的情况,再利用阈值分辨出有效数据和较大误差定位数据,消除较大误差对定位结果的干扰。综合运用一致性检验和极大似然估计,进行管道内部缺陷检测定位分析,通过试验对比分析可知,新的一致性检验算法具有良好的抗干扰性,其平均相对定位误差为0.212%,有效减少了里程轮定位的累积误差,实现了管道内部缺陷检测的高精度定位,满足管道内检测的实际工程需求。