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《制图学和地理信息科学》2013,40(1):47-60
Without a priori cell traversing cost data, conventional GIS-based techniques cannot be used to find minimum cost paths from specified starting points to specified ending points. However, in one class of problems where these costs do not exist a priori, it may be possible to derive them. This class of problems is characterized by the presence of an existing minimum cost path that is subject to the same traversing cost mechanics as the new path that is being contemplated. This study developed and evaluated linear programming-based techniques for deriving both isotropic and anisotropic traversing costs from existing minimum cost pathways. The derived costs can then be used to find minimum cost routes for new pathways that are subject to the same cost mechanics as the existing pathways. The techniques presented here were evaluated by applying them to situations found in the forest road network of the Arapaho and Roosevelt National Forests (ARNF) in Colorado. In 18 of the 19 situations evaluated, the predicted routes generated using the techniques presented here agreed with actual roads found in the ARNF. 相似文献
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The p‐median problem (PMP) is one of the most applied location problems in urban and regional planning. As an NP‐hard problem, the PMP remains challenging to solve optimally, especially for large‐sized problems. A number of heuristics have been developed to obtain PMP solutions in a fast manner. Among the heuristics, the Teitz and Bart (TB) algorithm has been found effective for finding high‐quality solutions. In this article, we present a spatial‐knowledge‐enhanced Teitz and Bart (STB) heuristic method for solving PMPs. The STB heuristic prioritizes candidate facility sites to be examined in the solution set based on the spatial distribution of demand and service provision. Tests based on a range of PMPs demonstrate the effectiveness of the STB heuristic. This new algorithm can be incorporated into current commercial GIS packages to solve a wide range of location‐allocation problems. 相似文献
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道路网络背景下的距离度量（如道路网络距离、旅行时间）是在空间分析或空间统计过程中常用的距离度量,但在科研过程中由于道路数据的可获得性和精度等方面的限制,该类距离的计算可能较为困难。Minkowski距离函数是欧氏空间中的广义距离函数,其参数p值的不同代表着对空间不同的度量。利用Minkowski的通用性和灵活性（参数p不同的取值）,研究如何更好地逼近道路网络距离。同时,探索不同道路网络的部分计量特征（如密度、弯曲度等）与最优p值之间的关系。实验证明,相对于最常用的欧氏距离度量,优选p值后的Minkowski距离函数能够更大程度上逼近道路距离。而通过对道路网络计量特征与最优p值之间的关系的分析,指出了弯曲度与最优p值之间的对应关系,它对于p值的选择具有重要的指导意义。此外,为了验证Minkowski距离逼近算法的可行性,以地理加权回归分析为例,通过对比传统的欧氏距离度量、最优Minkowski距离度量和道路网络距离（旅行时间）对模型解算结果的影响,指出优选后Minkowski距离一定程度上更接近于采用旅行时间对模型解算的结果。 相似文献
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针对雨雪雾天气影响下的动态路网最优路径问题,概括了天气影响行车的因子,基于停车视距模型进行了顾及天气影响的安全车速计算。在此基础上,将行车的时间和费用作为路阻,并结合现有交通模型,采用最大似然估计法确定了路阻函数,论述了在天气和交通状况已知的条件下,如何构建动态路网模型,并提出一种求解动态路网最优路径的算法。 相似文献
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阐述了GIS网络分析中不确定性选址问题的基本模型及特性。从问题的定义可知其为NP完备类问题。推导了最优解在紧条件的下界算法,并结合广义Powell算法及遗传算法,提出了不确定性选址问题的混合遗传算法,实验证明,在最优解的品质和收敛速度上都达到了比较好的效果。同时,实验的结果从另一个角度证明,如果兼顾收敛速度和解的品质这两个指标,单纯的遗传算法未必比其他搜索算法更优越,采用一些局部搜索性能较好的算法结合遗传算法,可以从两方面改善求解效果。 相似文献
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旅行商路径优化问题是经典的网络分析问题之一。由于旅行商问题具有NP Hard特性,主要通过智能优化方法或启发式算法来获得近似最优解。然而,单一智能优化方法存在运算量过大、参数选择苛刻,对初值依赖性强等缺陷,很难快速实现全局优化。结合多种优化机制和邻域搜索结构设计混合启发式算法可在一定程度上解决这一问题。本文结合遗传算法的全局寻优能力和禁忌搜索的记忆功能,设计实现了一种基于分散集中策略的禁忌遗传算法,即采用遗传变异算子作为分散策略构造邻域,开辟新的搜索空间,有效提升获得全局最优解的概率;将禁忌搜索作为集中策略进行局部寻优,避免迂回探测,充分体现禁忌搜索较强的“爬山”能力,并通过实际交通网络和不同规模的节点集合,从求解精度、稳定性和效率三个方面对算法进行了评价。结果表明,本文提出的交通网络旅行商路径优化的禁忌遗传算法平均求解精度比禁忌搜索算法提高了9%,略优于ArcGIS;当与ArcGIS求解的TSP路径长度差异在1%以内时,禁忌搜索算法已经难以获得对应精度的TSP路径,而禁忌遗传算法效率比遗传算法提高了50%。且禁忌遗传算法具有很好的并行化潜力。 相似文献
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Chris Brunsdon 《Transactions in GIS》2011,15(3):385-400
Following a brief review of the kernel regression approach to estimating surface models of the form z=f(x,y) +ε, this article will consider the situation where f is not a continuous surface function, and in particular where the discontinuities take the form of one‐dimensional breaks in the surface, and are not specified a priori. This form of model is particularly useful when visualizing some social and economic data where very rapid changes in geographical characteristics may occur – such as crime rates or house prices. The article briefly reviews approaches to this problem and proposes a novel approach (Bilateral Kernel Regression) adapting an algorithm from the field field of image processing (Bilateral Filtering), giving example analyses of synthetic and real‐world data. Techniques for enhancing the basic algorithm are also considered. 相似文献
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B. A. Gorbunov 《地理信息系统科学与遥感》2013,50(1):30-35
The mathematical basis for a feature classification algorithm is described which combines elements of game theory with Bayesian and suboptimal [feature classification] decision rules. Comparison of reflectance values with training area parameters, according to a sequence of diminishing a priori probabilities that the values will be assigned to that particular class results in reductions in computer time during classification. Results of the procedure are demonstrated through a pair of “before” and “after” images. Translated from: Metody kompleksnykh aerokosmicheskikh issledovaniy Sibiri, L. K. Zyat'kova, ed. Novosibirsk: Nauka, 1985, pp. 75–79. 相似文献
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CPT Clifford W. Greve 《Journal of Geodesy》1972,46(1):31-45
This paper discusses theory and results of an attempt to use non-linear programming methods to arrive at an optimal, in the
sense of least cost, solution to the design of a survey system to meet specified accuracy. In other words, the method determines
the combination of various types of observations which will yield the required accuracy of control points for a minimum cost.
The theoretical background of the procedure is discussed, and methods of extension to photo-grammetry and other sciences are
presented. Much of the paper is concerned with discussing results of numerical solutions for the optimal design of several
small, but typical, mapping problems.
It is believed that this research is original with the author, as extensive literature searches and correspondence has produced
no knowledge of prior research into this application of nonlinear programming. The method at its current state of development
appears to be capable of yielding significant improvements to the present concepts of survey network design. 相似文献
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为方便公众优化出行路径，规避或减少空气污染暴露损害，提出一种基于低空气污染暴露的健康出行路径动态搜索算法（dynamic healthy-route search algorithm，DHRSA），并设计开发了相应健康出行路线规划系统。该算法通过融合土地利用回归制图、暴露风险权重估算和Dijkstra最短路径搜索算法，基于实时空气污染情景动态规划健康出行路径。以长沙主城区为例进行随机车辆出行方式测试实验，通过比较DHRSA算法规划的健康出行路径与传统最短出行路径、最快出行路径的出行暴露风险，验证了该算法的可靠性与系统的实用价值。 相似文献
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X. X. Jin 《Journal of Geodesy》1997,71(7):411-422
This paper derives a DGPS positioning algorithm, referred to as the algorithm for carrier-adjusted DGPS positioning. This
algorithm can be applied by a DGPS user when code and carrier observations are available and when the dynamic behaviours of
both mobile positions and receiver-clock biases can and cannot be modelled. Since the algorithm directly uses code and carrier
observations, the stochastic model of observations has a simple structure and can be easily specified. When the dynamic behaviour
of mobile positions can be modelled, the algorithm can provide recursive solutions of the positions, on the other hand, when
the behaviour cannot be modelled, it can provide their instantaneous solutions. Furthermore, the algorithm can integrate with
a real-time quality-control procedure so that the quality of the position estimates can be guaranteed with a certain probability.
Since in the use of the algorithm there always exist redundant observations unless the position parameters are inestimable,
the quality control can even be performed when only four satellites are tracked. Using the algorithm and real GPS data collected
at a 100-km baseline, this contribution investigates how DGPS positioning accuracies vary with the type of observables used
at reference and mobile stations, and how important it is to choose an elevation-dependent standard deviation for code observations
in DGPS data reduction. It was found that using carrier observations along with code observations is more important at the
reference station than at the mobile station. Choosing an elevation-dependent standard deviation for code observations can
result in better positioning accuracy than choosing a constant standard deviation for code observations. For the 100-km baseline,
half-metre single-epoch positioning accuracy was achieved when dual-frequency data was used at both reference and mobile stations.
The positioning accuracy became better than 0.75m when the types of observable used at the mobile station were replaced by
L1 code and carrier.
Received: 9 April 1996 / Accepted: 6 February 1997 相似文献
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灾后城市交通运输能力下降，原有的流量分配方案不再适用。为保障正常的经济社会活动，本文提出了一种基于改进蚁群算法的交通流量分配方法。首先评估路网通行能力影响因素并建立道路质量评价体系，利用路段质量改进蚁群算法中的启发式因子；然后为扩大蚁群搜索范围加入随机节点并改进信息素的更新机制；最后应用改进算法对城市交通总量进行分批分配并得到流量分配图。结果表明，改进算法综合考虑了出行距离和道路质量，较改进前更符合交通流量分配要求，具有较好的路径寻优性，可为灾后救援工作和灾后路网交通分配决策提供建议和支持。 相似文献
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Identifying a route that avoids obstacles in continuous space is important for infrastructure alignment, robotic travel, and virtual object path planning, among others, because movement through space is not restricted to a predefined road or other network. Vector and raster GIS (geographic information system) solution approaches have been developed to find good/efficient routes. On the vector side, recent solution approaches exploit spatial knowledge and utilize GIS functionality, offering significant computational advantages in finding an optimal solution to this path routing problem. Raster‐based shortest path techniques are widely applied in route planning for wayfinding, corridor alignment, robotics and video gaming to derive an obstacle avoiding path, but represent an approximation approach for solving this problem. This research compares vector and raster approaches for identifying obstacle‐avoiding shortest paths/routes. Empirical assessment is carried out for a number of planning applications, highlighting representational issues, computational requirements and resulting path efficiency. 相似文献
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Qingquan Li Zhe Zeng Tong Zhang Jonathan Li Zhongheng Wu 《International Journal of Applied Earth Observation and Geoinformation》2011
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. 相似文献
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An optimum vehicular path algorithm for traffic network based on hierarchical spatial reasoning 总被引：5，自引：0，他引：5
Human beings' intellection is the characteristic of a distinct hierarchy and can be taken to construct a heuristic in the shortest path algorithms.It is detailed in this paper how to utilize the hierarchical reasoning on the basis of greedy and directional strategy to establish a spatial heuristic,so as to improve running efficiency and suitability of shortest path algorithm for traffic network.The authors divide urban traffic network into three hierarchies and set forward a new node hierarchy division rule to avoid the unreliable solution of shortest path.It is argued that the shortest path,no matter distance shortest or time shortest,is usually not the favorite of drivers in practice.Some factors difficult to expect or quantify influence the drivers' choice greatly.It makes the drivers prefer choosing a less shortest,but more reliable or flexible path to travel on.The presented optimum path algorithm,in addition to the improvement of the running efficiency of shortest path algorithms up to several times,reduces the emergence of those factors,conforms to the intellection characteristic of human beings,and is more easily accepted by drivers.Moreover,it does not require the completeness of networks in the lowest hierarchy and the applicability and fault tolerance of the algorithm have improved.The experiment result shows the advantages of the presented algorithm.The authors argued that the algorithm has great potential application for navigation systems of large-scale traffic networks. 相似文献
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Human beings’ intellection is the characteristic of a distinct hierarchy and can be taken to construct a heuristic in the shortest path algorithms. It is detailed in this paper how to utilize the hierarchical reasoning on the basis of greedy and directional strategy to establish a spatial heuristic, so as to improve running efficiency and suitability of shortest path algorithm for traffic network. The authors divide urban traffic network into three hierarchies and set forward a new node hierarchy division rule to avoid the unreliable solution of shortest path. It is argued that the shortest path, no matter distance shortest or time shortest, is usually not the favorite of drivers in practice. Some factors difficult to expect or quantify influence the drivers’ choice greatly. It makes the drivers prefer choosing a less shortest, but more reliable or flexible path to travel on. The presented optimum path algorithm, in addition to the improvement of the running efficiency of shortest path algorithms up to several times, reduces the emergence of those factors, conforms to the intellection characteristic of human beings, and is more easily accepted by drivers. Moreover, it does not require the completeness of networks in the lowest hierachy and the applicability and fault tolerance of the algorithm have improved. The experiment result shows the advantages of the presented algorithm. The authors argued that the algorithm has great potential application for navigation systems of large-scale traffic networks. 相似文献
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针对GPS,GLONASS,BDS组合导航系统定位中卫星的选择作了相关分析。首先用STK软件进行仿真,分析几何精度因子与卫星数的关系,得出组合导航系统最佳选星数;再根据卫星星座的空间几何分布,基于次优选星算法的成本函数模型,结合各导航系统卫星测量精度的差异性以及次优选星算法的峰值、不稳定特点,构建一种以卫星高度角和载噪比确定的加权成本函数模型,提出一种依据加权成本函数选星的分步次优加权选星算法。实验结果表明,该选星算法能近似到达最优选星算法的效果,计算负荷也相对较小,可满足导航定位解算精度和实时性要求。 相似文献