An Automated GIS Procedure for Delineating River and Lake Boundaries

Digitization of river and lake boundaries is an essential task in several hydrologic studies, which, in most cases, is performed manually by using aerial photographs. This paper presents an automatic geographic information system (GIS) procedure for delineating river and lake boundaries using aerial photographs. The GIS procedure is based on supervised classification of aerial photographs by using the National Hydrography Dataset (NHD) for creating training areas. Four study areas – Lake Palestine in Texas, Brazos River in Texas, Neuse River in North Carolina, and Snake River in Idaho – are used to demonstrate the approach. The results from the automatic boundary delineation process are evaluated by comparing them to manually digitized boundaries. The boundaries delineated by the automatic procedure matched the manually digitized boundaries with an overall difference of less than five percent in terms of area measurement. Besides saving about 85 percent of manual labor, the GIS procedure provides a consistent way of delineating water bodies, and provides estimation of river channel widths, which, in conjunction with existing NHD data, can be used to estimate average flow depths. Supplementing the regional scale NHD data with local scale attributes such as channel width and depth may lead to increased use of NHD in local scale studies.     

A GIS-based Investigation of Gaming Venue Catchments

Globally, the growth of the gambling industry in recent decades has raised questions about the potential for community costs associated with gambling development. In order to minimise the harms and maximise the gains for local, state and national economies, in many jurisdictions the industry is heavily regulated. Regulators rely upon a wide range of information sources to assist in decision making and are often concerned with issues that have socio‐spatial characteristics. Despite this, there have been few applications of geographical information systems (GIS) to gambling behaviour. This paper trials the use of a GIS‐based approach to investigate one aspect of gambling regulation, namely the spatial characteristics of gaming venue catchments. The research was conducted in a suburban region of Canberra, Australia. The results from the study show that the catchment areas of gaming venues can vary considerably and are more complex than previous studies have suggested. The regulatory implications of the findings are discussed as well as possible avenues for further GIS‐based research into gambling.     

Creating a GIS application for retail centers in Jeddah city

The aim of this paper is to identify the role of geographical information systems (GIS) in supporting retail planners in monitoring and analyzing retail development and growth. At first, a review about retail planning and its relevant issues is made. Second, GIS is defined together with its applications in retail planning. The third part discusses the created GIS application that is designed for two retail centers in Jeddah city, Saudi Arabia. This application is created to help planners in defining the distribution of retail demand, describing customers profile, analyzing trade areas and modeling retail flows. Two useful models have been produced by this study. One is called market penetration and the other is based on spatial interaction technique. The former is created to examine retail center catchment area, while the latter is used to model the interaction between demand areas and retail centers.     

Comparative Study of Approaches to Delineating Built‐Up Areas Using Road Network Data

Delineated built‐up areas may be used for applications such as navigation, database enrichment and the identification of urban sprawl. As more road network data have become available, many studies have considered using road network data to delineate built‐up areas. This study investigated the three existing approaches to delineating built‐up areas on a map: the grid‐based approach, kernel density analysis and an approach based on street blocks. These approaches are evaluated and compared from three angles. First, two measures were proposed to quantitatively evaluate the land area of the delineated built‐up areas; second, a questionnaire was designed to visually compare the representations of the delineated built‐up areas; and, third, the time complexity of using each approach was tested. The three approaches were applied to different sets of road network data for New Zealand; data from buildings and residential areas were used as benchmarks. The results showed that: (1) in a quantitative assessment, both the grid‐based approach and kernel density analysis can usually detect more built‐up areas than the approach based on street blocks; (2) on visual inspection, most of the students who completed the questionnaire performed the representations using the approach based on street blocks; and (3) in time complexity, the approach based on street blocks always takes the least time.     

WaterNet: A GIS Application for the Analysis of Hydrologic Networks Using Vector Spatial Data

Traditionally, stream and sub‐watershed characterization in GIS has been accom‐ plished using a DEM‐based terrain analysis approach; however, there is a large amount of existing vector hydrographic data difficult to accurately reproduce using DEMs. WaterNet is a GIS/hydrologic application for the integration and analysis of stream and sub‐watershed networks in vector format. Even with vector data, hydrologic inconsistencies between streams and sub‐watersheds do exist, and are revealed in the form of streams crossing drainage divides and sub‐watersheds with more than one outlet. WaterNet rectifies these inconsistencies and couples the two datasets. Most algorithms involving traces of dendritic networks employ a form of tree traversal which requires topologic information to be organized into specialized data structures. On the contrary, WaterNet develops topologic relationships from GIS attribute tables, which, in combination with sorting and querying algorithms, make the calculation process efficient and easy to implement. With the topologic relationships of the streams and sub‐watersheds, WaterNet can perform traces to calculate cumulative network parameters, such as flow lengths and drainage areas. WaterNet was applied to the catchment of the Texas Gulf coast for a total of 100 cataloging units (411,603 km²) and 60,145 stream lines (183,228 km).     

Integrated Mobile GIS and Wireless Internet Map Servers for Environmental Monitoring and Management

With the progress of mobile GIS technology there is a great potential for adopting wireless communications and Internet mapping services for regional environmental management programs and natural habitat conservation. This paper provides an overview of a NASA-funded research project that focuses on the development of mobile GIS tools and wireless Internet Map Server (IMS) services to facilitate environmental monitoring and management tasks. By developing and testing wireless web-based map/image servers, mobile GIS applications, and global positional systems (GPS), this research created an integrated software/hardware infrastructure for a prototype mobile GIS application. The mobile GIS prototype allows multiple resource managers and park rangers to access large-size, remotely sensed images and GIS layers from a portable web server mounted in a vehicle. Users can conduct real-time spatial data updates and/or submit changes back to the web server over the wireless local area network (WLAN). This paper discusses in general the major components of mobile GIS, their current technological limitations, and potential problems during implementation. Key research agenda for mobile GIS are identified with suggestions for future research and development.     

A New GIScience Application for Visualized Natural Resources Management and Decision Support

This article presents two decision support plug‐ins in free GIS software: ArcGIS Explorer Desktop. The ubiquitous WebGIS Analysis Toolkit for Extensive Resources (uWATER) focuses on providing GIS analysis functions: spatial and attribute queries in the public services tool for users with limited access to commercial GIS software. The interface of uWATER is general enough to support decision‐making in numerous management issues in natural resources, economics and agriculture. The uWATER‐Pumping Assessment (uWATER‐PA) toolkit, on the other hand, is an extended package targeting the specific environmental issue of groundwater pumping impacts. The uWATER‐PA package is an excellent alternative to evaluating complex groundwater pumping assessment issues before investing significant time, labor, and funds in monitoring and detailed scientific study. It incorporates simulation of the physics of groundwater flow and user interaction into GIS software. A graphical user interface makes both data entry and interpretation of results intuitive to non‐technical individuals. Results are presented as colored drawdown maps and can be saved in GIS format for future dissemination. The impact of drawdown on existing wells can be characterized and mapped, through the use of uWATER's spatial query capabilities and the drawdown maps generated by uWATER‐PA.     

Assessing Raster GIS Approximation for Euclidean Shortest Path Routing

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.     

基于OGC Web服务模型的城市异构GIS互操作

利用服务共享实现城市异构GIS系统互操作是解决互操作问题的一个新思路。本文首先分析了开放地理信息系统联盟(OGC Open GIS Consortium)的互操作模型(OWS Open GIS Web Service)的框架结构以及服务协作,然后以模型框架中的一个基本数据服务———地图要素服务(Web Feature Service)为例,详细介绍了利用服务共享实现城市异构GIS数据共享与互操作的具体开发过程,最后对该模式的应用前景进行了分析。     

An Integrated GIS Approach to Accessibility Analysis

Accessibility is an important element in evaluating existing land‐use patterns and transportation services, predicting travel demands and programming transportation investments in urban transportation planning. This paper presents an integrated GIS approach to accessibility analysis, which provides a general framework for integrated use of GIS, travel impedance measurement tools and accessibility measures to support the accessibility analysis process, including formulating the concept of accessibility, selecting or developing accessibility measures, specifying the accessibility measures, deriving the accessibility values using the selected or developed accessibility measures, and presenting and interpreting the accessibility values. An integrated GIS tool, ACCESS, designed for implementing the integrated approach is also described and illustrated.     

基于GIS的连锁企业商品配送服务

主要研究了基于GIS的连锁商业企业的商品配送服务信息系统中的一个基本问题———如何根据居民点的服务请求确定配送商品的连锁商店。首先根据引力模型对连锁商店的服务域进行了讨论,在忽略了连锁商店的规模影响的基础上,导出了Voronoi多边形的商店服务域,并确定了由最邻近居民点的连锁商店提供商品配送服务的原则。于是问题转化为如何快速计算最邻近居民点的连锁商店的技术问题。我们提出了Voronoi多边形空间查询的新方法,通过与点对欧氏距离、缓冲区结合欧氏距离两种方法的比较,证明了Voronoi多边形空间查询的高效率,新方法的应用显著地提升了应用系统的效率。     

GIS in Participatory Research: Assessing the Impact of Landmines on Communities in North-west Cambodia

The view of GIS, adopted by many, as an undemocratic and divisive technology is perhaps most poignant in settings where financial and skills‐based resources are limited, notably in lower‐income countries. Where those countries are also recovering from a period of military conflict there would at first sight seem to be little opportunity for employing GIS as part of a socially‐sensitive approach to ‘development’. This paper explores the potential for using GIS in participatory approaches to gathering and analysing geographical information on human‐environment interactions in post‐conflict settings. We discuss empirical work from northwest Cambodia where GIS and participatory methods have been integrated to assess risk to local communities from landmines and to develop priorities for landmine clearance. In juxtaposing ‘official’, spatially‐referenced data with indigenous geographical knowledge in this study we seek to privilege meaningful geographical understandings over conventional notions of spatial ‘accuracy’. In so doing we carry out a Participatory Mine Impact Assessment (PMIA) to explore spatial activities among local populations in mine‐contaminated communities and to help identify improved strategies for returning refugees in re‐establishing livelihoods.     

Catchment infiltration II: Contributing areas

This study considers two issues of interest to the hydrologic and geographical information systems community. One deals with identifying the spatial distribution of infiltration and runoff contributing areas. The other addresses process modelling within a GIS framework. The study operates on the premise that partitioning of precipitation into runoff or infiltration depends on rainfall intensity and on soil properties. The problem is that neither local rainfall intensity, nor soil properties such as infiltration capacity and macroporosity are known well enough for all points of a catchment and need to be estimated. We infer local intensity from the interpolated distribution of cumulated rain depths over the catchment and record duration at the official met site. Measured values of sorptivity and hydraulic conductivity define infiltration. Negative head infiltration describes macroporosity. To scale-up measured point values to larger areas and to model infiltration and macropore continuity at a catchment scale we use geostatistical kriging and conditional simulation together with standard GIS techniques of overlay manipulation. Results delineate areas contributing to runoff and infiltration and relate them to macroporosity. By intersecting overlays of precipitation with those of infiltration we create alternate GIS masks targeting specific portions of the watershed as either runoff or infiltration contributing zones. Choice of cell size and time interval define the scales of averaging for the application. Kriged surfaces illustrate the distribution of catchment infiltration, while conditional simulation provides a mechanism to define model uncertainty.     

Natural Conversational Interfaces to Geospatial Databases

Natural (spoken) language, combined with gestures and other human modalities, provides a promising alternative for interacting with computers, but such benefit has not been explored for interactions with geographical information systems. This paper presents a conceptual framework for enabling conversational human‐GIS interactions. Conversations with a GIS are modeled as human‐computer collaborative activities within a task domain. We adopt a mental state view of collaboration and discourse and propose a plan‐based computational model for conversational grounding and dialogue generation. At the implementation level, our approach is to introduce a dialogue agent, GeoDialogue, between a user and a geographical information server. GeoDialogue actively recognizes user's information needs, reasons about detailed cartographic and database procedures, and acts cooperatively to assist user's problem solving. GeoDialogue serves as a semantic ‘bridge’ between the human language and the formal language that a GIS understands. The behavior of such dialogue‐assisted human‐GIS interfaces is illustrated through a scenario simulating a session of emergency response during a hurricane event.     

A New 3‐D Solar Radiation Model for 3‐D City Models

Estimates of solar radiation distribution in urban areas are often limited by the complexity of urban environments. These limitations arise from spatial structures such as buildings and trees that affect spatial and temporal distributions of solar fluxes over urban surfaces. The traditional solar radiation models implemented in GIS can address this problem only partially. They can be adequately used only for 2‐D surfaces such as terrain and rooftops. However, vertical surfaces, such as facades, require a 3‐D approach. This study presents a new 3‐D solar radiation model for urban areas represented by 3‐D city models. The v.sun module implemented in GRASS GIS is based on the existing solar radiation methodology used in the topographic r.sun model with a new capability to process 3‐D vector data representing complex urban environments. The calculation procedure is based on the combined vector‐voxel approach segmenting the 3‐D vector objects to smaller polygon elements according to a voxel data structure of the volume region. The shadowing effects of surrounding objects are considered using a unique shadowing algorithm. The proposed model has been applied to the sample urban area with results showing strong spatial and temporal variations of solar radiation flows over complex urban surfaces.     

Skyline和ExtJS的企业级三维GIS设计

企业级三维GIS不仅能实现地理数据和空间服务共享,还能以三维方式直观地展现复杂的空间数据。本文提出了一种基于Skyline和ExtJS的企业级三维GIS设计方案。该方案在Skyline软件已有的三维GIS功能基础上,利用ExtJS开发地理数据和空间服务共享模块。论文详细说明了方案的具体设计方法,并结合实际应用验证了方案的可行性与有效性。     

地理信息系统开发方法的演进

随着计算机科学和软件工程技术的进步 ,GIS软件工程方法在不断地演进 ,越来越适合于GIS的开发。文中介绍和回顾了GIS在自身的发展过程中使用的一些软件工程方法 ,并初步探讨了为GIS项目选用软件开发方法的问题。     

Inferring the home locations of Twitter users based on the spatiotemporal clustering of Twitter data

Residential locations play an important role in understanding the form and function of urban systems. However, it is impossible to release this detailed information publicly, due to the issue of privacy. The rapid development of location‐based services and the prevalence of global position system (GPS)‐equipped devices provide an unprecedented opportunity to infer residential locations from user‐generated geographic information. This article compares different approaches for predicting Twitter users' home locations at a precise point level based on temporal and spatial features extracted from geo‐tagged tweets. Among the three deterministic approaches, the one that estimates the home location for each user by finding the weighted most frequently visited (WMFV) cluster of that user always provides the best performance when compared with the other two methods. The results of a fourth approach, based on the support vector machine (SVM), are severely affected by the threshold value for a cluster to be identified as the home.     

从市场需求看我国高校GIS教学改革

总结了GIS技术和高校GIS专业的发展,分析了GIS的学科特点和GIS教育的特点。进而在分析当前市场对GIS人才的需求状况及对GIS人才提出的要求的基础上,阐述了现有GIS教育存在的问题,从教学内容、教学方法、教学模式和考试方法等方面提出了GIS教学改革的一些设想。