Applications of graph theory to gross error detection for GPS geodetic control networks     

Samwel Katambi  Guo Jiming  Kong Xiangyuan 《地球空间信息科学学报》2013,16(4):26-31

This paper describes a broad perspective of the application of graph theory to establishment of GPS control networks whereby the GPS network is considered as a connected and directed graph with three components. In this algorithm the gross error detection is undertaken through loops of different spanning trees using the “Loop Law” in which the individual components ΔX, ΔY and ΔZ sum up to zero. If the sum of the respective vector components ΩX, ΩY and ΩZ in a loop is not zero and if the error is beyond the tolerable limit (ε>ω), it indicates the existence of gross errors in one of the baselines in the loop and therefore the baseline must be removed or re-observed. After successful screening of errors by graph theory, network adjustment can be carried out. In this paper, the GPS data from the control network established as refence system for the HP Dam at Baishan county in Liaoning province is presented to illustrate the algorithm.  相似文献   

A fewest-turn-and-shortest path algorithm based on breadth-first search     

Yan Zhou  Weisheng Wang  Di He  Zhe Wang 《地球空间信息科学学报》2013,16(4):201-207

Many cognitive studies have indicated that the path simplicity may be as important as its distance travelled. However, the optimality of paths for current navigation system is often judged purely on the distance travelled or time cost, and not the path simplicity. To balance these factors, this paper presented an algorithm to compute a path that not only possesses fewest turns but also is as short as possible by utilizing the breadth-first-search strategy. The proposed algorithm started searching from a starting point, and expanded layer by layer through searching zero-level reachable points until the endpoint is found, and then deleted unnecessary points in the reverse direction. The forward searching and backward cleaning strategies were presented to build a hierarchical graph of zero-level reachable points, and form a fewest-turn-path graph (G*). After that, a classic Dijkstra shortest path algorithm was executed on the G* to obtain a fewest-turn-and-shortest path. Comparing with the shortest path in Baidu map, the algorithm in this work has less than half of the turns but the nearly same length. The proposed fewest-turn-and-shortest path algorithm is proved to be more suitable for human beings according to human cognition research.  相似文献   

Applicability of the Modified Universal Soil Loss Equation for prediction of sediment yield in Khanmirza watershed,Iran     

《水文科学杂志》2013,58(5):1068-1075

Abstract

The present study aims to estimate the sediment yield due to storm rainfall and runoff at the outlet of the Khanmirza watershed (395 km²) located in western Iran. The estimation was made for six storm events using the Modified Universal Soil Loss Equation (MUSLE). All the inputs required for the application of the model were determined through runoff and sediment concentration monitoring at the time of storm events, and field surveys in the study area. The applicability of the model to the study area was then evaluated by comparison of its estimates with those calculated using the measured sediment data. The results of the study demonstrated the efficiency of the MUSLE in estimating storm-associated sediment yield except one storm event in the study area with a high level of agreement and non-significant differences between mean estimated and measured values in the study storm events.  相似文献   

A Franco-American Geographical Encounter     

《The Professional geographer》2013,65(3):367-368

ATLAS?GRAPHICS (Version 3.0).

AutoCAD (Release 9.0 with ADE+1, ADE+2 and ADE+3).

AutoSketch (Speed Enhanced Version 1.02).

NUMERICAL RECIPES FORTRAN. Numerical Recipes Software

SCIPLOT.  相似文献   

A graph-based algorithm to define urban topology from unstructured geospatial data     

J.-P. de Almeida  J.G. Morley  I.J. Dowman 《International journal of geographical information science》2013,27(8):1514-1529

Interpretation and analysis of urban topology are particularly challenging tasks given the complex spatial pattern of the urban elements, and hence their automation is especially needed. In terms of the urban scene meaning, the starting point in this study is unstructured geospatial data, i.e. no prior knowledge of the geospatial entities is assumed. Translating these data into more meaningful homogeneous regions can be achieved by detecting geographic features within the initial random collection of geospatial objects, and then by grouping them according to their spatial arrangement. The techniques applied to achieve this are those of graph theory applied to urban topology analysis within GIS environment. This article focuses primarily on the implementation and algorithmic design of a methodology to define and make urban topology explicit. Conceptually, such procedure analyses and interprets geospatial object arrangements in terms of the extension of the standard notion of the topological relation of adjacency to that of containment: the so-called ‘containment-first search’. LiDAR data were used as an example scenario for development and test purposes.  相似文献   

如何运用GeoMAG软件使图件结构规范化——以贵州省分幅实际材料图为例     

邬晓芳  邓毅  王常薇  况忠 《贵州地质》2012,29(2):156-159

根据《全国矿产资源潜力评价数据模型规范》要求,图件结构模型包括图件名称、图件代码、图件分层、图件比例尺、坐标系参数、图层对应属性数据表、属性数据项代码等,全国矿产资源潜力评价项目办开发了GeoMAG软件来帮助大家更快、更好的规范图件。笔者在工作过程中视不同情况分别采用生成图件结构和规范图件结构两种方法对图件进行规范化处理,使提交的图件符合《全国矿产资源潜力评价数据模型规范》要求。  相似文献   

资料缺失河道水质风险分析          下载免费PDF全文

顾文权  邵东国 《水科学进展》2012,23(1):74-79

资料缺失是进行水质风险分析的薄弱环节。结合水质指标浓度分布的先验信息及已有水质资料,在分析水质指标相关关系基础上建立其随时间变化的浓度分布模型,应用Bayes理论及Gibbs抽样方法对模型涉及的大量参数和超参数的统计特征进行了同步估计。在假定缺失数据为随机变量的基础上,应用该方法得到的大量样本较好实现了对缺失数据的估计,并结合风险分析理论进一步量化了水质超标风险。通过实例验证了模型的合理性,为资料缺失地区的水质风险分析提供了新的思路和方法。  相似文献   

基于水流阻力与图论的河网连通性评价   总被引：6，自引：0，他引：6       下载免费PDF全文

徐光来  许有鹏  王柳艳 《水科学进展》2012,23(6):776-781

河网连通是区域防洪、供水和生态安全的重要基础。基于图论将河网概化为图模型,考虑不同类型河道输水能力差异,以河道水流阻力倒数表征水流通畅度,并以河道水流通畅度为权值,借助ArcGIS平台建立河网图模型加权邻接矩阵,再利用MATLAB工具进行顶点水流通畅度计算和河网连通度分析,从而实现对河网连通性的定量化分析。以太湖流域嘉兴平原河网为例,进行河道疏浚前后的河网连通程度定量评价,结果表明河道疏浚后河网连通度明显增加。  相似文献   

图划分对Arc-flags算法的影响     

刘惠民  孙广中  周英华 《地球信息科学学报》2016,18(11):1456-1464

最短路径计算作为导航的常用算法在移动互联网中扮演了重要角色,由于路网规模的增大和终端的不停移动,传统的串行最短路径算法已经无法满足实时性要求,因此预处理技术得到了广泛使用。Arc-flags是一个经典的基于预处理技术的最短路径算法,可以提供高效的在线最短路径查询服务。现有Arc-flags算法的研究主要集中在提升预处理时空效率和比较不同路网划分方式的优劣上,尚未见图划分对Arc-flags算法影响的深入研究。本文在真实路网上测试了不同的图划分数量和边界点数量等因素对Arc-flags算法的影响,主要包括预处理时间和空间的消耗、在线查询时间和搜索范围等方面,并根据实验结果和分析提出了合理的图划分建议（如选用好的图划分方法减少边界点数量等）,为改进和使用Arc-flags算法提供指导。  相似文献   

浅谈GPS技术在"竿影日照图"测量中的应用     

詹瑞超  王丽君 《测绘与空间地理信息》2004,27(5):75-76

按照规划原理的要求,利用GPS定位技术测定本地区“竿影日照图”,用以规范和指导城市规划中建筑物、构筑物等的日照间距问题,同时对GPS观测中的体会加以总结。  相似文献