Open source, spatial analysis, and activity-travel behaviour research: capabilities of the aspace package

This paper reports on recent experience with the development of aspace, an Open Source (OS) library for the geographic visualization and analysis of activity-travel behaviour. The paper begins with an overview of recent progress with respect to the convergence of Open Source technology, spatial analysis, and travel behaviour research. The remainder of the paper focuses on aspace; a collection of functions that, when combined with data describing the geographical location of daily activities, can be used to visualize and describe spatial properties of individual and household activity spaces. These properties include: size, orientation, shape, and the geographical dispersion of activity locations contained within the activity space. Several planar geometries are used to transform measurable spatial properties into intuitive objects for visualizing spatial patterns of activity participation. Experiments are conducted, using data from the first wave of the 2003 Toronto Travel Activity Panel Survey, to demonstrate the potential application of aspace for basic and applied policy-based research into activity-travel behaviour. The toolkit is distributed as a downloadable ‘package’ from the Open Source R Project for Statistical Computing.      

顾及道路通达性和时间成本的多用户位置推荐

位置推荐是地理社交网络的重要应用,针对城市范围内多用户集体社交活动的规划需求,在顾及道路通达性和时间成本的情况下进行位置推荐算法的研究。针对城市路网结构特征和导航路线规划特点,在地图应用程序接口的支持下,利用各用户间导航路线上的特定点自动识别、构建区域实现位置推荐,平衡多个用户到推荐地点的可到达性和时间成本。实验结果验证了所提方法的有效性,在地理社交网络上可以为城市多用户的集体活动提供有效的位置推荐方案。     

The utility of travelling when destinations are heterogeneous. How much better is the next destination as one travels further?

In many studies travel behaviour (for example, commuting) is analysed on the basis of a utility function with the distance (d) travelled as one of the arguments. An example is U=U(d,Y-cd,T-td) where Y and T denote money and time constraints, and c and t money and time costs per unit distance. This standard approach is not without problems, however, since it ignores the fundamental fact that most transport has a derived character: travelling kilometres is not an activity that gives utility per se, but only because these kilometres bring people to certain places they want to visit. In this paper we develop a method that provides a justification for utility functions such as shown here by showing that these can be made consistent with theories that take into account the derived character of transport.     

基于时序逻辑的多Agent系统协商模型及其推理与授权规则研究

在文献[1]的基础上,对多Agent系统协商模型基于时序逻辑的方法进行了设计,给出了其形式化体系结构,同时给出了该模型的推理规则和授权规则。     

An Agent‐Based Simulation of Residential Location Choice of Tenants in Tehran,Iran

Residential location choice modeling is one of the substantial components of land use and transportation models. While numerous aggregated mathematical and statistical approaches have been developed to model the residence choice behavior of households, disaggregated approaches such as the agent‐based modeling have shown interesting capabilities. In this article, a novel agent‐based approach is developed to simulate the residential location choice of tenants in Tehran, the capital of Iran. Tenants are considered as agents who select their desired residential alternatives according to their characteristics and preferences for various criteria such as the rent, accessibility to different services and facilities, environmental pollution, and distance from their workplace and former residence. The choice set of agents is limited to their desired residential alternatives by applying a constrained NSGA‐II algorithm. Then, agents compete with each other to select their final residence among their alternatives. Results of the proposed approach are validated by comparing simulated and actual residences of a sample of tenants. Results show that the proposed approach is able to accurately simulate the residence of 59.3% of tenants at the traffic analysis zone level.     

Human dynamics in space and time: A brief history and a view forward

This article highlights the key intellectual development in human dynamics research, examines the modeling emphases in publications, and argues for research directions in need. Human dynamics research is discussed in two broad directions: spacing time and timing space, to model human activities and interactions. Time is essential to human dynamics research. Space, while often being overlooked, in complement with time is critical to understanding human dynamics because knowing where activities take place is essential to knowing how and why people act and interact. Some interactions allow remote or asynchronized participations, and others require movement to collocate individuals for participating in synchronized activities. A spacing time approach examines the temporal gaps between interactions. A timing space approach investigates the spatial pulses between interactions. Primary research in the spacing time of human dynamics established queueing theories to explain the bursts and heavy‐tailed distribution of human interactions. Although research on the timing space of human dynamics enjoys growing popularity with data from geo‐tagged social media and location‐aware social internet of things (SIoT), its publications remain mostly exploratory. This article suggests a hierarchical framework to systematically study human dynamics and relate findings to build the body of knowledge about human dynamics.     

Space-time accessibility measures: A geocomputational algorithm with a focus on the feasible opportunity set and possible activity duration

 Space-time accessibility measures have received much attention in recent years due to their sensitivity to differences in individual ability to participate in activities in space and time. Despite the conceptual attractiveness and robustness of space-time measures, only few attempts have been made to operationalize them to date. Research that seeks to improve space-time accessibility measures is still sorely needed. This study seeks to enhance space-time accessibility measures through developing a new operational method and GIS-based algorithm that better represents the space-time characteristics of urban opportunities (e.g. their geographical distribution and opening hours) and human activity-travel behavior (e.g. delay times, minimum activity participation time, and maximum travel time threshold). The proposed method not only takes into account the number and size of opportunities, but also the possible activity duration at each activity location given its opening hours and the effect of transport network topology (e.g. one-way streets, turn restrictions and over-pass). Incorporating these elements into space-time measures helps overcome several shortcomings of previous approaches to evaluating space-time accessibility. Received: 15 September 2002 / Accepted: 10 February 2003 A version of this paper was presented at the 98th Annual Meeting of the Association of American Geographers, Los Angeles, March 19-23, 2002. We thank Joe Weber for providing the digital transport network with travel speeds and a version of the geocomputational algorithm he used in his study (Weber 2001), upon which our developmental effort has been based. We are also grateful to the helpful comments and suggestions of the reviewers.     

Monitoring Invasive Species: Detecting Purple Loosestrife and Evaluating Biocontrol along the Niobrara River,Nebraska

Geospatial tools and techniques are playing important roles in determining the location and spatial extents of invasive species infestations and in evaluating the performances of various management activities aimed at controlling their spread. In this study, hyperspectral image processing techniques were used to map purple loosestrife and to assess the effectiveness of biological control agents in controlling its infestations along the Niobrara River in Nebraska. Validation based on field survey showed an overall map accuracy of 82.1% and comparison with in situ data on biocontrol release indicated that biocontrol agents were effective in the areas where they were released.     

利用X射线脉冲星进行同步定位/授时的可观性分析

将星载时钟钟差增广为状态向量,根据非线性系统的可观性秩条件判据,从理论上证明了利用X射线脉冲星进行同步定位/授时是可观的,为X射线脉冲星自主导航的工程应用提供了理论依据。     

Towards a conjoint-based, context-dependent model of task allocation in activity settings: Some numerical experiments

 None of the currently developed activity-based models of transport demand explicitly models task allocation among household members. To fill this gap, the present paper suggests to complement activity-based models of activity scheduling with a context-dependent model of task allocation. That is, it is assumed that the allocation of tasks within households is partly based on such contextual variables as the amount of time a member has to spend on mandatory activities and car availability. In particular, the paper advocates a conjoint-based approach, based on an assignment task as opposed to the traditional ranking, rating or choice response formats. By definition, an assignment task involves a combinatorial explosion of choice alternatives, implying that additional operational decisions to estimate the context-dependent model are required. This study presents the results of various numerical experiments, conducted to better understand the impacts of those decisions on the degree of bias in the parameter estimates of the choice model. The results of these simulations indicate that under particular assumptions, the development and estimation of a conjoint-based, context-dependent model of task allocation within households is feasible. Received: March 1999 / Accepted: June 2001     

Nonlinear regional economic dynamics: continuous-time specification,estimation and stability analysis

This paper presents an innovative approach to the study of regional economic dynamics within a nonlinear continuous-time econometric framework—a generalized specification of the Lotka–Volterra system of equations. This specification, which accounts for interdependent behavior of three industrial sectors and spillover effects of activities in neighboring regions, is employed in an analysis of five Italian regions between 1980 and 2003. For these regions, we report estimation results, characterize the varying systems dynamics, analyze the models’ local and global stability properties, and determine via sensitivity analyses which structural features appear to exert the greatest influence on these properties.

Deriving rules from activity diary data: A learning algorithm and results of computer experiments

 Activity-based models consider travel as a derived demand from the activities households need to conduct in space and time. Over the last 15 years, computational or rule-based models of activity scheduling have gained increasing interest in time-geography and transportation research. This paper argues that a lack of techniques for deriving rules from empirical data hinders the further development of rule-based systems in this area. To overcome this problem, this paper develops and tests an algorithm for inductively deriving rules from activity-diary data. The decision table formalism is used to exhaustively represent the theoretically possible decision rules that individuals may use in sequencing a given set of activities. Actual activity patterns of individuals are supplied to the system as examples. In an incremental learning process, the system progressively improves on the selection of rules used for reproducing the examples. Computer experiments based on simulated data are performed to fine-tune rule selection and rule value update functions. The results suggest that the system is effective and fairly robust for parameter settings. It is concluded, therefore, that the proposed approach opens up possibilities to derive empirically tested rule-based models of activity scheduling. Follow-up research will be concerned with testing the system on empirical data. Received: 31 January 2001 / Accepted: 13 September 2001     

Partitioning Spatial Model Uncertainty Based on Joint Spatial Simulation

In this study, an uncertainty analysis procedure for joint sequential simulation of multiple attributes of spatially explicit models used in geographical informational systems was developed based on regression analysis. This procedure utilizes information obtained from joint sequential simulation to establish the relationship between model uncertainty and variation of model inputs. Using this procedure, model variance can be partitioned by model input parameters on a cell by cell basis. In the partitioning, the correlation of neighboring cells is accounted for. With traditional uncertainty analysis methods, this is not possible. In a case study, spatial variation of soil erodibility from a joint sequential simulation of soil properties was analyzed. The results showed that the regression approach is a very effective method in the analysis of the relationship between variation of the model output and model input parameters. It was also shown for the case study that: (1) the uncertainty of soil erodibility of a cell is mainly propagated from its own soil properties; (2) the interactions of soil properties of neighboring cells could reduce uncertainty of soil erodibility; (3) it is sufficient for uncertainty analysis to include the nearest three neighboring cell groups; and (4) the largest uncertainty contributors vary by soil properties and location.     

灾害应急远程协同会商系统的设计与集成

传统的电视电话会议,由于空间地域差异或者专业知识的限制,使信息沟通不完整,表述复杂,给会商参与者造成沟通交流障碍。在此基础上,增加分布式地理信息系统,可以使异地参会者实时协作完成各类专题地图制作,增强参会者对会商内容的快速理解,沟通更加便捷,提高会商质量。本文提出灾害应急会商中会议发起人——参会者模式的地图协同标绘应用,研究了会商期间的标绘消息网络推送,实现异地用户对图形标绘信息的远程同步感知,设计了协同编辑指定图元的并发控制流程,分析图元标绘并发操作时的冲突可能性,并提出系统自动裁决、用户协商、权威仲裁的避免冲突策略。文章以玉树地震为应用实例,讲述了民政部利用本系统将远程专家会商结果绘制了物资调配态势图,实现了辅助决策。     

Positioning Disaster Relief Teams Given Dynamic Service Demand: A Hybrid Agent‐Based and Spatial Optimization Approach

During extreme events, like hurricanes, it is essential to position relief services for non‐evacuees throughout the affected region in optimal locations. While previous research has explored a variety of spatial optimization models to accomplish such a task, most work assumes that the population with demand is relatively static. However, this assumption neglects to account for potential feedbacks in the relief distribution system. For example, a population's behavior can both affect and be affected by the placement of relief services, resulting in a dynamic spatial distribution of demand. This article presents a hybrid modeling approach that utilizes GIS data with agent‐based and spatial optimization models to position emergency relief teams in Bay County, Florida during a hurricane event. Non‐evacuating household agents choose to remain at home or seek shelter, while relief team agents are periodically repositioned to account for changes in the spatial distribution of household agents. A total of 220 simulations are run to explore a variety of scenarios. Results show different repositioning timing strategies and the magnitude of the feedback effect drastically changes the level of access households have to relief teams. Ultimately, this work demonstrates the importance of accounting for behavioral and spatial dynamics in disaster relief distribution systems.     

Monte Carlo simulations of the impact of troposphere,clock and measurement errors on the repeatability of VLBI positions

Within the International VLBI Service for Geodesy and Astrometry (IVS) Monte Carlo simulations have been carried out to design the next generation VLBI system (“VLBI2010”). Simulated VLBI observables were generated taking into account the three most important stochastic error sources in VLBI, i.e. wet troposphere delay, station clock, and measurement error. Based on realistic physical properties of the troposphere and clocks we ran simulations to investigate the influence of the troposphere on VLBI analyses, and to gain information about the role of clock performance and measurement errors of the receiving system in the process of reaching VLBI2010’s goal of mm position accuracy on a global scale. Our simulations confirm that the wet troposphere delay is the most important of these three error sources. We did not observe significant improvement of geodetic parameters if the clocks were simulated with an Allan standard deviation better than 1 × 10⁻¹⁴ at 50 min and found the impact of measurement errors to be relatively small compared with the impact of the troposphere. Along with simulations to test different network sizes, scheduling strategies, and antenna slew rates these studies were used as a basis for the definition and specification of VLBI2010 antennas and recording system and might also be an example for other space geodetic techniques.     

GPS测时在电力系统中的应用

介绍了利用GPS测时及时间传递的几种方式，详细地讨论了GPS用在电压相角测量，输电线路故障定位以及线路网损和电能结算系统几个方面的应用原理，设计出应用的方案，并得到部分结果。     

Margin-based feature selection for hyperspectral data

A margin-based feature selection approach is explored for hyperspectral data. This approach is based on measuring the confidence of a classifier when making predictions on a test data. Greedy feature flip and iterative search algorithms, which attempts to maximise the margin-based evaluation functions, were used in the present study. Evaluation functions use linear, zero–one and sigmoid utility functions where a utility function controls the contribution of each margin term to the overall score. The results obtained by margin-based feature selection technique were compared to a support vector machine-based recurring feature elimination approach. Two different hyperspectral data sets, one consisting of 65 bands (DAIS data) and other with 185 bands (AVIRIS data) were used. With digital airborne imaging spectrometer (DAIS) data, the classification accuracy by greedy feature flip algorithm and sigmoid utility function was 93.02% using a total of 24 selected features in comparison to an accuracy of 91.76% with full set of 65 features. The results suggest a significant increase in classification accuracy with 24 selected features. The classification accuracy (93.4%) achieved by the iterative search margin-based algorithm with 20 selected features using sigmoid utility function is also significantly more accurate than that achieved with 65 features. To judge the usefulness of margin-based feature selection approaches, another hyperspectral data set consisting of 185 features was used. A total of 65 selected features were used to evaluate the performance of margin-based feature selection approach. The results suggest a significantly improved performance by greedy feature flip-based feature selection technique with this data set also. This study also suggest that margin-based feature selection algorithms provide a comparable performance to support vector machine-based recurring feature elimination approach.     

基于GIS的车险查勘调度客户端的设计与实现

车辆保险公司对路面查勘车辆的调度以及事故现场的查勘效率是体现公司服务水平的关键。近年来,一些保险公司已逐步试点车辆查勘定损无纸化和车辆调度自动化管理。本文运用无线互联网、GoogleMapsAPI等技术,基于Android平台开发移动查勘定损客户端,实现调度指令接收、信息录入与查询、拍照取证、信息上传、实时定位跟踪、路径规划等功能;根据车险查勘调度模型研究成果,运用Flex,WebService等多种Web技术,基于SuperMapiServer平台开发室内调度客户端,实现网络地图可视化、地图量测、现场查勘信息接收与查询、查勘车辆调度等功能。     

Using Eye-tracking and Mouse Metrics to Test Usability of Web Mapping Navigation

The growth of web-based mapping is transforming geovisualization. Use of web mapping has become ubiquitous throughout much of the world and has sparked greater public interest in GIS and mapping. Despite the rapid growth of web mapping, there has been relatively little study of the design and usability of web maps. Moreover, the design and function of popular web mapping programs are sometimes at odds with standard GIS and cartographic practices for even the simplest of functions such as zooming into a feature of interest. This study advances understanding of web mapping design via web usability testing based on mouse metrics and eye tracking technology to assess the utility of four different web map navigation schemes: pan zoom; double clicking; zoom by rectangle; and wheel zoom. We found significant differences among the various interfaces, with marked preference for the standard GIS approach of rectangle zoom, followed closely by wheel zoom. Far fewer users preferred the web mapping standard of pan zoom or click zoom. In addition to finding significant differences in usability among these approaches, this work illustrates the broader utility of usability testing and eye tracking technology for creating a better web mapping experience for users.