Polygon-to-Polygon Spatial Accessibility Using Different Aggregation Approaches: A Case Study of National Forests in the US Mountain West Region

Spatial accessibility is an enduring topic of spatial analysis that is intimately tied to issues of spatial representation and scale. A variety of methods to measure accessibility have been developed with most research focusing on metropolitan‐sized spatial extents using census‐defined aggregation units and relying on vector point representation to calculate Euclidean or network distances as key ingredients in measure formulations. Less research considers broader scales where both origin and destination points are treated as polygons. This research develops alternative gravity‐based measures of polygon‐to‐polygon accessibility for a case study of county‐level accessibility to national forests in the western US. Different methods of county and forest representation are implemented using census block centroids and a lattice approach for disaggregation and re‐aggregation. Other characteristics that are analyzed include origin‐destination linkage definitions, population weighting, and distance thresholds. Correlation analysis is used to assess relationships of alternative measures with a simple percentage measure and with each other. Low correlations would suggest that measures capture different aspects of accessibility that are related to their qualitative characteristics. Results show the alternative measures to be dissimilar from the percentage measure; however, high correlations among alternative measures suggest that there is little to differentiate certain disaggregated measures in spite of their richer qualitative interpretation.     

Individual accessibility and distance from major employment centers: An examination using space-time measures

 Distance has often been assumed to be an influence on intraurban accessibility, whether in traditional proximity-based measures of accessibility, or through expectations about distance-minimizing travel behavior and the logic of the monocentric model. This paper examines the importance of distance from major employment centers to individual accessibility in Portland, Oregon, using space-time accessibility measures computed using GIS. The results of this research indicate that distance from these locations has mixed results on individual accessibility. This appears to reflect the importance of time, both the time of day activities are scheduled as well as time constraints, to individual activity patterns. Received: September 2002 / Accepted: January 2003 The author gratefully acknowledges the contributions of two anonymous reviewers, whose comments greatly improved the content of this paper     

三维地图式可视化大数据

数据可视化技术利用计算机图形图像学以及数据挖掘技术,以交互方式将数据中的隐藏信息展示给用户,为用户决策提供参考。近年来,随着PC计算能力与互联网技术的快速发展,传统的数据可视化技术已无法满足人们日益增长的信息处理需求。目前,数据可视化在可视化过程中存在显示结果精确度低、表达方式单一、不能突出数字信息内含的规律性等问题。本文针对上述问题提出了基于三维地图的可视化大数据解决方案,该方案通过制作专题地图可视化数据,对数据的规律性进行了研究,从而方便用户理解数据的深层次信息,发现隐藏的特征、模式、趋势等信息。     

Integrating Sketch Maps with GIS to Explore Fear of Crime in the Urban Environment: A Review of the Past and Prospects for the Future

Understanding the spatial dimension of fear of crime in the urban environment is important to understanding behaviors in response to this concern. Making this connection between perception and action has long been a goal of scholars in the social and health sciences, though this complex relationship has yet to be fully elucidated. Specifically, in studies on fear of crime and its influence on behavior, a variety of definitions and methods have been employed. This situation has yielded insights, as well as inconsistencies. In the past decade, Geographic Information Systems (GIS) has been added to this methodological mix, though it too has contributed limited understanding of the environmental perception-behavior nexus. During this time, some scholars have integrated a traditional technique for accessing environmental perception, the sketch map, with this newer technology. This article provides a review and critical assessment of the way GIS has been used to understand fear of crime, specifically through the integration of sketch maps. This focus is framed by an overview of substantive and methodological concerns and concludes with a discussion of continued research needs. As behavioral responses to fear of crime are acknowledged to impact physical and mental health and overall well-being, in addition to the viability of neighborhoods, research in this area will continue apace. However, for integration of sketch maps in GIS to be a valuable methodological contributor to this line of inquiry, users of the approach must understand its complexities. This article outlines these issues so that they may be considered in future research and may improve the ability for this approach to yield new understanding of fear of crime.     

Challenges in applying capacitated covering models

Service system planning has long been supported by location‐covering models designed to address access and accessibility issues. An important aspect of many systems is limits on service, often conceptualized as facility capacities. Much research can be found that proposes modeling approaches and solution techniques to account for capacitated covering problems, and commercial GIS software exists that is capable of structuring and applying facility service limits. This article reviews issues and challenges associated with the application of capacitated covering models, including critical evaluation of allocation approaches and GIS capabilities. Case studies involving service provision in two cities in California—San Jose and Santa Barbara—are provided to highlight associated issues faced in practice. While user‐friendly commercial software makes it easy to access capacitated cover models, there remain challenges for addressing underlying considerations and assumptions in practice.     

山地遥感主要研究进展、发展机遇与挑战

山地遥感是研究在山地这一特定环境中的遥感基本原理、方法及其应用的科学技术。从山地遥感研究的基本内涵出发,总结面临的若干前沿科学问题,指出当前主要研究内容:(1)电磁波与山地地表相互作用机理及建模理论;(2)山地遥感数据时—空—谱归一化处理方法;(3)山地地表信息遥感建模、反演与同化方法;(4)山地遥感尺度效应与算法/产品验证;(5)山地遥感信息综合应用等。从山地遥感研究的基础理论方法以及山地遥感应用两个层面回顾了近年来山地遥感研究取得的进展,并就新时代背景下山地遥感研究面临的机遇与挑战进行了分析,最后对山地遥感研究前景进行了展望。     

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.     

Accessibility tradeoffs in public transit planning

 Spatial accessibility is a critical consideration in the provision of services, both public and private. In public transit planning, accessibility is comprised of access and geographic coverage. Interestingly, these two considerations are somewhat at odds with each other. Access is important because it is the process associated with getting to and departing from the service. Such access is typically perceived of in spatial terms as the physical proximity to transit stops or stations. Additional stops along a route usually mean greater access, because a stop is more likely to be within an acceptable walking/driving standard for a larger number of people. On the other hand, more stops and greater access slow transit travel speeds, thereby decreasing the area of service reachable given a travel time budget. More stops along a route translate to greater service interruption and longer travel times. The faster the travel time, the more desirable the service. Further, if travel times become excessive, then user demand for service will decrease. All of this means that stop spacing along a route is central to accessibility, as it is a tradeoff of access (more stops) and geographic coverage (service efficiency through less stops). This paper details modeling approaches for addressing accessibility concerns in an integrated fashion. Bus-based transit service in Columbus, Ohio will be utilized to illustrate the usefulness of these approaches in transit planning. Received: September 2002 / Accepted: January 2003 This research was supported in part by an Ohio State University seed grant.     

Evaluating the importance of accessibility to congestion response using a GIS-based travel simulator

 This paper examines the effect of accessibility on individual response to unexpected traffic delays and congestion. The dataset used was collected by means of a travel simulator developed within a geographic information system (GIS) environment. The simulator models a commute trip where congestion takes place, and subjects are asked to respond by making a choice among alternative courses of action. Available alternatives for dealing with the unexpected traffic delay include changing the location of the planned activities or changing the activities to be performed. Accessibility to the new locations and to the different activities is computed using a cumulative measure. Analysis using CHAID tree technique found that accessibility is a good predictor of subjects' choice when responding to unexpected traffic delays. Received: September 2002 / Accepted: January 2003 Support for this research by a grant from the Center of Intelligent Transportation Research of the Ohio State University is gratefully acknowledged. The author would also like to thank Joe Weber, Mei-Po Kwan and two anonymous reviewers for their valuable comments.     

Assessing representation error in point-based coverage modeling

 Accurately representing geographic space in a digital environment continues to confound and challenge researchers. Carrying out spatial analysis in a setting where geographic representation is subject to change poses problems to be addressed. In this paper we examine spatial representation in the context of coverage-based location modeling. A geographic region can be represented in a variety of ways. We present an evaluation of spatial representation in the location of facilities that provide coverage oriented services. The analysis shows that the modeling results are sensitive to how spatial demand for service is represented in a digital environment. We develop an approach for evaluating representational appropriateness. This research contributes to spatial analysis integrated in geographic information system environment. Received: 10 January 2001 / Accepted: 8 April 2002     

基于分形的图像场表达与图像处理应用

分形图像处理理论是一个尚未形成而又亟待研究的图像处理新理论，本文研究此理论中的几个基本理论问题：３－Ｄ自然景物表面２－Ｄ投影图像的分形投影关系；图像的分形场表达及其适宜性评价，文中以假设检验理论定量地分析了分形场表达的适宜性，并提出以拟合度Ｘ＾２检验法作为确定图像分形场无标度区间的统计量化指标，据此讨论了分形应用于图像处理的基本技术与方法，给出了分形在图像纹理分析，特征提取，目标探测和区域分割等领     

Emerging and vector-borne diseases: Role of high spatial resolution and hyperspectral images in analyses and forecasts

 Many infectious diseases that are emerging or transmitted by arthropod vectors have a strong link to landscape features. Depending on the source of infection or ecology of the transmitting vector, micro-habitat characteristics at the spatial scale of square meters or less may be important. Recently, satellite images have been used to classify habitats in an attempt to understand associations with infectious diseases. Whether high spatial resolution and hyperspectral (HSRH) images can be useful in studies of such infectious diseases is addressed. The nature of questions that such studies address and the desired accuracy and precision of answers will determine the utility of HSRH data. Need for such data should be based on the goals of the effort. Examples of kinds of questions and applications are discussed. The research implications and public health applications may depend on available analytic tools as well as epidemiological observations. Received: 30 July 2001 / Accepted: 14 October 2001     

Intelligent Visualisation and Information Presentation for Civil Crisis Management

This paper describes an ongoing research work on developing methods for effective visualisation support for situation analysis, decision making, and communication in the course of disaster management. The major goals are to reduce the information load of the analyst, decision maker, or information recipient without omission of anything important and to ensure quick and accurate comprehending of the information. The work embraces the issues of selection of the relevant information and defining the appropriate level of detail, data preparation (aggregation and other transformations), and selection of the appropriate methods for visual representation depending on the user's tasks or communication goals, recipient's profile, and the target presentation medium. A practical outcome from the research will be a knowledge base that can be used to support analysis, decision making, and information communication in emergency situations. A great part of the knowledge, specifically, knowledge on data transformation and representation, is generic and can be used for different applications.     

虚拟地理环境的认知研究框架初探

作为新一代地理分析工具,虚拟地理环境对于增强人类地理认知、分析解决地理问题方面具有显著优势。目前虚拟地理环境的基本框架、实现技术均有较多论述与成果。但在虚拟地理环境的认知研究方面尚缺乏有效指导。为提高虚拟地理环境构建的科学性,本文通过对虚拟地理环境现有概念的分析,提出从系统论角度进行虚拟地理环境认知研究的观点;并对虚拟地理环境的认知与地理认知、地图认知等相近概念进行了对比分析。从现实环境与虚拟环境间的相似性入手建立了虚拟地理环境的认知研究框架,该框架从思维相似、感觉相似、几何相似、特性相似和离散相似5个方面探讨了虚拟地理环境认知研究目前的着眼点,并将思维相似作为虚拟地理环境认知研究的重点与难点。该框架将虚拟地理环境的认知问题置于一个更广泛背景中进行研究,一方面体现了虚拟地理环境所具有的地理实验研究新平台的作用,另一方面重点强调了人的作用,对深入开展虚拟地理环境的研究具有重要意义。     

Addressing location uncertainties in GPS‐based activity monitoring: A methodological framework

Location uncertainty has been a major barrier in information mining from location data. Although the development of electronic and telecommunication equipment has led to an increased amount and refined resolution of data about individuals’ spatio‐temporal trajectories, the potential of such data, especially in the context of environmental health studies, has not been fully realized due to the lack of methodology that addresses location uncertainties. This article describes a methodological framework for deriving information about people's continuous activities from individual‐collected Global Positioning System (GPS) data, which is vital for a variety of environmental health studies. This framework is composed of two major methods that address critical issues at different stages of GPS data processing: (1) a fuzzy classification method for distinguishing activity patterns; and (2) a scale‐adaptive method for refining activity locations and outdoor/indoor environments. Evaluation of this framework based on smartphone‐collected GPS data indicates that it is robust to location errors and is able to generate useful information about individuals’ life trajectories.     

MODELING OF GEOGRAPHIC INFORMATION: CONTRIBUTION TO A NEW METHODOLOGICAL PARADIGM

The methodological problems encountered in geosystems modeling in an automated medium are discussed on the basis of general GIS applications in human geography. Geographic information modeling is examined as a new methodological paradigm, the basis for which is the symbiosis between a research geographer and a computer. Specific examples are used to demonstrate the potential for use of such modeling to solve basic and applied problems in social and economic geography. Translated by Edward Torrey, Alexandria, VA 22308 from: Izvestiya Akademii Nauk, seriya geograficheskaya, 1996, No. 2, pp. 124-130.     

千兆网支持下的城市公众GIS

当前GIS技术的发展已经进入到一个新的阶段,呈现出网络化、专业化、智能化、大众化等特点。公众GIS是近年来新兴的GIS应用领域,它主要的目的是面向公众提供信息服务。介绍了城市公众GIS的基本概念、特点和系统功能,在分析了当前公众GIS存在的问题之后,继而提出一种适合宽带网络(千兆以太网)支持下的公众GIS系统结构,并进一步分析了它的功能和用途。     

Dynamic GIS Case Studies: Wildfire Evacuation and Volunteered Geographic Information

Incorporating the temporal element into traditional GIS is a challenge that has been researched for many years and has many proposed solutions. The implemented system "Extended Dynamic GIS" or EDGIS is based on the "geo-atom" and Space Time Point (STP). EDGIS provides a platform for spatiotemporal data representation, storage, and query in order to address the need for a dynamic GIS to manage complex geographic data types. The system has the capability of executing spatiotemporal object interaction queries (OIQs) such as crossing and coincidence of field-objects and object-fields. In this article existing dynamic GIS analysis techniques are further improved and enhanced through exploration of more in-depth case studies. Further examined here are applications to wildfire evacuation modeling and travel scenarios of urban environments with individuals providing volunteered geographic information (VGI). The EDGIS platform provides a means for interacting with a range of dynamic geographic phenomena. The areas of transportation, location based services (LBS), hazards, and geo-sensor networks provide challenges intertwined with the above applications as well as additional challenges pertinent to the ongoing GIScience research topic of spatiotemporal GIS. Using EDGIS to explore the described case studies of wildfire evacuation as well as VGI provides the advancements described above and demonstrates implemented uses for dynamic GIS.     

The GIS/SA interface for substantive research(ers): A critical need

This paper is concerned with the intersection of GIS and spatial analysis, its accessibility for scientists who may be less methodologically oriented than others, and its use in substantive research driven by theoretical, conceptual, and empirical issues central to one's discipline. GIS/SA use in this manner has lagged considerably. The case is documented, that there may be shifts in this trend is noted, and suggestions for moving ahead more quickly are put forth. These include instructional efforts, software development, and substantive research that will provide a demonstration effect, guide, and direction for others.     

Finding outdoor boundaries for 3D space‐based navigation

Outdoor navigation is widely used in daily life, but faces various issues related to the fidelity of outdoor navigation networks. For instance, agents (pedestrians) are often guided via unrealistic detours around places without clear paths (e.g., squares) or if there are vertical constraints such as overpasses/bridges. This is partly explained by the fact that the main sources of navigation networks in current outdoor navigation are two‐dimensional road/street networks. Utilizing a three‐dimensional space‐based navigation model, compatible with some indoor approaches, is a popular way to address the above‐mentioned issues. A 3D space‐based navigation model is generated by treating 3D spaces as nodes and the shared faces as edges. Inputs of this model are enclosed 3D spaces (volumes). However, outdoor spaces are generally open and unbounded. This article puts forward an approach to enclose outdoor spaces and mimic the indoor environments to derive a network based on connectivity and accessibility of spaces. The approach uses 2.5D maps and consists of three major steps: object footprint determination, footprint classification and space creation. Two use cases demonstrate the proposed approach. Enclosing outdoor spaces opens a new research direction toward providing seamless indoor/outdoor navigation for a range of agents.