internet based gis · 2016. 5. 12. · Internet GIS, Web-Based GIS or Online GIS 11 The Structure...

Shilpam Pandey and Jon HarborEarth and Atmospheric Sciences,Purdue University, West Lafayette, IN 47907Phone: +1-765-49-40258, Fax: +1-765-49-61210,E-mail: [email protected]

Bernard EngelAgricultural and Biological EngineeringPurdue University, West Lafayette, IN 47907Phone: +1 765 49-41198, Fax: +1-765-49-61198,E-mail: [email protected]

INTERNET-BASEDGEOGRAPHICINFORMATIONSYSTEMSAND DECISION-SUPPORT TOOLS

The Urban and Regional Information Systems Association1460 Renaissance Drive, Suite 305Park Ridge, IL 60068

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Copyright ©2000 by the Urban and Regional Information Systems Association (URISA), 1460 Renaissance Drive,Suite 305, Park Ridge, IL 60068, (847) 824-6300, www.urisa.org.

All rights reserved including the rights of reproduction and use in any form or by any means, including the making ofcopies by any photo process or by any electronic or mechanical device (printed, written, or oral), or recording forsound or visual reproduction, or for use in any knowledge or retrieval system or device, unless permission in writing isobtained from the copyright proprietor.Printed in the United StatesISBN #: 0-916848-20-5

Introduction 5

Chapter 1: The Internet, Geographic InformationSystems and Decision Support Tools 7

Chapter 2: Advantages of Internet-Based tools 9

Chapter 3: Serving Web-Based GIS and Decision Support Tools 11Internet GIS, Web-Based GIS or Online GIS 11The Structure of a Web-Based Approach 11Server-Side Approach 11Client-Side Approach 12

Chapter 4: Software Development Platform Examples 13ESRI 13Intergraph 14Autodesk 14MapInfo 14

Chapter 5: Sample Implementation of anInternet-based Decision Support Tool 17

The Tool 17The Team 18

Team Leaders 18GIS Professionals 18Land Use Planners 18Programmers 18

Serving the Tool over the Internet 18Programming Issues 18

Spreadsheet Version 19GIS Version 20

TABLE OF CONTENTS

Chapter 6: Mapping and User Interface Issues 23

Chapter 7: Conclusion 27List of Figures 27

About the Authors 29

Look-up table for Internet GIS terminology 31

References 35

Internet-Based Geographic Information Systems 5

Rapid growth of the Internet over the past decade hasopened up exciting new ways to supply data, tools,models, and other information to potential users.Internet delivery provides opportunities to increasethe involvement of stakeholders in the decision-making and planning process by providingknowledge and data through a widely accessible, fast,cost-effective, and easy-to-use medium.

There are significant advantages to making planningand decision-support tools accessible on the Internet.The wide availability of models, decision-supporttools, and databases on the Internet has the potentialto empower users, allowing them to identify site-specific options that meet their needs and to performanalyses of alternative scenarios. In addition, users ofInternet-based decision-support tools do not needexpensive software such as Geographic InformationSystem (GIS) tools or large databases on their localsystems, rather they have access to these resourcesthrough their web browser. Thus, even when users

have very limited resources, decisions can still bemade that take advantage of decision-support toolsincluding GIS capabilities, advanced models andtools, and spatial data at various scales.

This Quick Study provides readers with anunderstanding of the availability and the potential ofutilizing existing Internet resources, and preparesthem to use the next generation of Internet-baseddecision-support tools. For readers interested indeveloping new Internet-based tools, this Quick Studydiscusses approaches and challenges involved insetting up and implementing a decision-support tool,using a Purdue University project as an in-depth casestudy. The Quick Study is intended both forprofessionals interested in learning about currentlyavailable types of Internet-based decision-supporttools and for those involved in developing orextending geographic information and analyticalcapabilities over the Internet.

INTRODUCTION


CHAPTER 1:THE INTERNET, GEOGRAPHICINFORMATION SYSTEMS, ANDDECISION-SUPPORT TOOLS

There has been a phenomenal increase in the use ofthe Internet over the past decade, across a wide varietyof fields. The Internet has emerged as a major forcein global communications, journalism, commerce,science, publishing, and many other fields (Plewe1997). Similarly, the use of GISs has also increaseddramatically, moving from being a tool used largelyin academics by researchers in the fields of spatialanalysis, geosciences, and planning to a tool used incommercial organizations and by the general publicto locate addresses, homes, businesses, and performvarious other spatial queries as the basis for decision-making. GIS data and functionalities available overthe Internet are rapidly changing the way peopleobtain, retrieve, share, and use spatial information tomake decisions.

The Internet has emerged as an essential technologyfor allowing the public to access, process, anddisseminate all kinds of information to the public. Itserves as a tool for various agencies and organizationsincluding local, state, and federal authorities todisseminate information, it has helped raise awarenesslevels and it has increased participation leading tomore informed and democratically made decisions(Craig 1998). The broad base and wide access of the

Internet offers the promise of increased levels ofpublic participation that will help sustain morecompetent decision-making (Klein 1999). The rapidlyincreasing number of individuals going on-line andthe even faster growth in the number of companiesgoing on-line have made the Internet an integral partof society. Access to the Internet and the easy usabilityof the World Wide Web (WWW) have created apowerful means for persons to exchange and processinformation (Peng 1999). The Internet presentsnumerous possibilities to supply data, tools, models,and other information to potential users. It providesa ready-made platform in the sense that it offers aninterface that the vast majority of persons understandand one that is intuitive rather than taught. ReachingGIS clients on the Internet allows developers toleverage widespread existing knowledge (Singh 1999).This approach also provides opportunities to increasethe involvement of stakeholders in the decision-making and planning process by providingknowledge and data through a widely accessible, cost-effective, and easy-to-use medium. Making GIS-based tools accessible on the Internet allows a muchlarger dissemination of the analysis and resultscompared to the traditional stand-alone desktop GIS.By making such information easily available, the

8 Internet-Based Geographic Information Systems

general public can directly access the information andbe a part of the decision-making process.

Access to spatial data over the Internet for use on aGIS located on a personal computer was an importantfirst step. However, accessing GIS capabilities withouthaving data and GIS software on a computer, butinstead through the web, is becoming the next majoradvance. With the growth of application serviceproviders in other industries, a similar trend in thegeospatial industry is logical. McKee (2000) in hispaper “Catch the Internet Wave” recommendsencouraging new businesses to solve existingproblems using GIS and suggests the concept of GISapplication service providers. As this idea is adopted,there will likely be a boom in the use of spatial datafor an array of decisions, ranging from finding newhomes and locating schools and hospitals inneighborhoods to managing and providing utilitiesand other services on-line. For example, severalapplications involving dynamic mapping,information distribution, and on-line decision-

support tools were used by the South CarolinaDepartment of Transportation when Hurricane Hugostruck in the early 1990s.

The time, cost, and responsibilities involved inoperating and maintaining a web site have beengreatly reduced in recent years because of servicesnow being offered by web-hosting services. Smallorganizations can use these service companies tomaintain Internet sites and to get access to high-bandwidth connections, programmers, and othersupport staff. Thus, with the increase in GIS use bythe general public in the form of identifying fastestand shortest traffic routes (http://www.mapquest.com/), locating automatic tellermachines (http://www.visa.com/pd/atm/main.html),and providing neighborhood facilities informationand an increase in web-hosting services that ease theburdens of providing such services, a dramaticincrease in the availability of GIS applications throughthe Internet is the inevitable next step.


CHAPTER 2:ADVANTAGES OF INTERNET-BASEDTOOLS

Making GIS-based planning and decision-supporttools Internet accessible provides several significantadvantages over more traditional approachesincluding:

■ Users are not required to have GIS software andother database analysis tools on their desktopcomputers, and users with limited resources canmake decisions that take advantage of GIScapabilities and spatial data at various scales.

■ Clients of a centralized Internet-based GIS ordecision-support tool are not required tofrequently upgrade or change software on theirdesktop computer. Combined with savings frominitial software set-up costs, this can result insignificant economic advantages, especially forsmall organizations.

■ Providing models and other such decision-support tools from a centralized system or overthe Internet significantly simplifies themaintenance and distribution of such tools. It alsoensures that all users are using the same versionof a particular model or tool.

■ Databases are stored and maintained atcentralized locations. This provides for uniformdata access and use. In addition, the job ofmaintaining, updating, and changing suchdatasets is considerably simplified. Users of suchdatabases are not burdened with preparing andstoring large datasets on their desktop computers.

■ Data used for running and obtaining results fromsuch models can be verified. This reduces errorsdue to discrepancies in input data.

■ Applications requiring intensive computationand data can be run on powerful serversaccessible through the Internet rather than lessadept desktop computers.

■ The availability of models, decision-supporttools, and databases on the Internet has thepotential to empower users, allowing them toidentify site-specific options that meet their needsand perform analyses of alternative scenarios. Itprovides the public with tools with which to reachan informed decision on a given problem.

■ The availability of significantly advancedcapabilities with a simple Internet connection atno extra cost for software, data acquisition, andan easy-to-use Graphical User Interface (GUI)provides tremendous advantages for increasinguse of such tools.


CHAPTER 3:SERVING WEB-BASED GIS FUNCTIONSAND DECISION-SUPPORT TOOLS

Internet GIS, Web-based GIS, or On-lineGISThe Internet is a world-wide interconnected networkinfrastructure that hosts several applications andfacilitates the sharing of information around theglobe. It has been particularly valuable in encouraginginteroperability and promoting the concept of openand free exchange of data and information. TheInternet is composed of multiple, geographicallywidespread networks connected throughcommunications devices and sets of commoncommunications protocols. The World Wide Web(WWW) is a specific HyperText Transfer Protocol(HTTP) that runs on the Internet along with otherapplications such as e-mail and File Transfer Protocol(Peng 1999). Terms such as Internet GIS (Peng 1999),web-based GIS (Doyle et al 1998), on-line GIS, andDistributed Geographic Information (Plewe 1997)describe GIS functionalities that are increasinglyavailable via the Internet. Although in the strictestsense, each of these terms represents somethingslightly different, they are all used to denote similarfunctions. For a detailed discussion of technical termsused to describe Internet-accessible GIS terms, seePeng (1999).

The Structure of a Web-based GISThe basic structure of a web-based GIS or decision-support tool begins with a client who sends a requestto a server via a web browser using a Graphical UserInterface (Figure 1). A Map Server then activates theGIS software and decision-support tool and processesthe request. Figure 1 shows the basic structure of therelationship between the clients, the tools used forserving the maps and functionalities, and the GISsoftware and databases that are used.

The two basic methods of serving GIS and decision-support tools over the Internet are the server-sideapproach and the client-side approach. Server-sideapplications rely on a GIS server to manage GIS dataand perform analyses. A client-side applicationprocesses requests and GIS functionalities on theuser’s desktop computer.

Server-Side ApproachWith the server-side approach, the GIS softwareresides on the server and the browser acts as a GUI atthe client end. The client accesses GIS functionalitiesthrough the browser. The user requests or initiates afunction over the Internet to the server, which thenactivates GIS software which in turn processes the


Figure 1. Client Server architecture for a Web-Based GIS

request and sends results back to the user via thebrowser. A mediator is needed in this process becausethe HyperText Markup Language (HTML), whichforms the building blocks for the WWW, cannotcommunicate with GIS software directly. The mostcommonly used interpreter is the Common GatewayInterface (CGI). The CGI receives user input andparses (translates) this into a usable format for GISprograms. It facilitates the handling of informationrequests and acts as a gateway for providingappropriate information and creating documents onthe fly. By using CGI scripts, the web server canprovide information in a comprehensible format forclients and provides a gateway for interaction betweenthe client and server. CGI scripts basically handle thedata exchange between and web and GIS servers. Thescript is launched when the user sends a request. TheGIS software is started and runs the analysis requestedby the client. It receives output data from GIS softwareand returns it to the browser for presentation to theclient (Plewe 1997, Peng 1999).

Concentrating the workload on the server has severaladvantages. The most important of these is that itprovides for centralized hardware and software set-up that can be easily maintained and updated. Thisensures that all users have uniform access to the mostrecent version of a particular tool. The downside ofthis arrangement is that “simultaneousoversubscription” of the site (an unexpected numberof users flooding the site with requests at the sametime) could slow the system and discourageprospective users. In the server-side processingapproach, rather than having basic functions carried

out at the user end, each request made by the client,irrespective of whether it is a simple pan or zoomfunction or a more complex analysis, requires theserver to run the application and respond with results.This occupies server time and can slow the procedureand, in some cases, the response time.

Client-Side ApproachIn the client-side approach, the GIS analysis and modelsare executed locally on the user’s own computer. Theclient uses the Internet to download data, GIS software,and models from the server onto the local machine.Small, executable applications such as Java applets andActiveX controls are created that broaden thecapabilities of HTML to handle spatial maps and data.These are comparable to CGI scripts in the server-sideapproach. These applications do not require separateinstallation processes, can be downloaded at runtime,and are executable within the web server.

The decision whether to utilize a client-side or aserver-side approach requires the developers to finda balance or a trade-off that best suits the particularneeds of the user. Some of the issues that must beconsidered are: the target audience and the needs andthe requirements of this audience; the capabilities ofthe providers themselves; the speed of connectionavailable; and the anticipated number of personsaccessing the site at a given time. Generally, a client-side approach works best when there are largenumbers of users but little demand for advanced GIS-type analysis capabilities. A server-side approach suitsa clientele that is not very large and that requiresspecialized GIS analysis functions (Plewe 1997).


CHAPTER 4:EXAMPLES OF SOFTWAREDEVELOPMENT PLATFORMS

There are a variety of products available on the marketto serve GIS functions and maps on the Internet. Bythe sheer nature of a rapidly changing and expandingfield, there are many varied players and it is impossibleto provide a complete overview of all the toolsavailable in the market. To give a sense of some of whatis available at the time that this Quick Study wasprepared, examples of tools provided by fourcompanies are discussed here: EnvironmentalSystems Research Institute (ESRI, at http://www.esri.com/), Intergraph (http://www.intergraph.com/dynamicdefault.asp), MapInfo(http://www.mapinfo.com), and Autodesk (http://www3.autodesk.com/adsk/). Discussion of aparticular tool is not an endorsement of that product.

ESRIESRI currently offers four applications that buildupon their desktop GIS software.■ ArcView Internet Map Server (IMS) (http://

www.esri.com/software/arcview/extensions/imsect.html) is an image-based application thatcan be used in conjunction with the ESRIArcView GIS software. ArcView IMS publishesany map that can be generated with ArcView. Itrequires ArcView GIS Version 3.0, or higher,

running under Windows 95, Windows NT, orUNIX. It is shipped as an extension of ArcViewthat is a wizard that can reproduce mapsgenerated within ArcView and publishes them onthe web. It can also be used as an ESRI Map webserver extension that handles web client requestsand as MapCafe, which is a Java applet that residesin the browser and offers basic tools to browse,explore, and query maps on the Internet. Thisprovides the end user with a familiar ArcView-like interface and is relatively fast to set up.

■ MapObjects IMS (http://www.esri.com/software/mapobjects/ims/index.html) is also animage-based application. The MapObjectsInternet Solutions Kit includes three integratedapplications: MapObjects IMS, MapObjectsProfessional, and ArcExplorer. Maps can beserved via MapObjects IMS by creating a projectin ArcExplorer and executing IMS Catalog, IMSLaunch, and IMS administrator. The componentMapObjects administrator then serves the mapon the web with an ArcExplorer interface.Advanced users can build custom applications byusing development environments such as VisualBasic, Delphi, Visual C++, and other object-oriented programming languages.


■ RouteMap IMS is useful for organizations thatneed to add map routing capabilities to their websites. Unique symbols can be created to representvarious points of interests for users. This allowsusers to plot and print route maps to locationswithin the continental United States. At the timeof writing, it is only for use within thesegeographic limits.

■ Arc IMS (http://www.esri.com/software/arcims/index.html) is an extension to ArcInfo that allowsusers to combine data from local computers withdata located on remote servers. The user cancreate HTML and Java client versions throughArcIMS and customize client-side capabilitiesusing object-oriented programming languagessuch as Java Script and Visual Basic.

Intergraph■ GeoMedia Web Map (http://

www.intergraph.com/software/geo_map/geo_web_4.asp) reads data from a wide varietyof CAD (Computer-Aided Design) and GISformats. This is particularly useful fororganizations that have and use maps in theseformats and need to view them simultaneously.In addition to Intergraph formats, GeoMedia WebMap reads ArcInfo, ArcView, Oracle SpatialCartridge/Spatial Data Option, and other formatsdirectly. Versions to be released promise to be ableto receive data from AutoCAD, MapInfo, andStructured Query Language (SQL) server dataservers as well. GeoMedia Web Map delivers datato the client in a highly compressed vector formatcalled ActiveCGM. This ensures faster delivery tothe browsers. Descriptive information can also belinked to map features through standardrelational database techniques to createhyperlinked features that are accessible to clientsusing a standard web browser. GeoMedia WebMap permits users to combine raster and vectorinformation within the same map.

■ GeoMedia Web Enterprise (http://www.intergraph.com/gis/) is a tool that givesaccess to complex spatial analysis tools usingraster data. It lets users create dynamic, customweb-mapping applications to analyze andmanipulate geographic data. The server softwareincludes several sample applications that can beused for routing, crime analysis, rezoningnotification, and site selection. GeoMedia WebEnterprise builds on GeoMedia Web Map toprovide an entire series of spatial and networkanalysis objects and services that assist in thesmart distribution of data over the web.GeoMedia Web Enterprise objects are designedto work with industry-standard programminglanguages such as Visual Basic, Visual C++,PowerBuilder, and Delphi. They can use Java-based scripting as the development environment.

Autodesk■ MapGuide (http://www3.autodesk.com/adsk/

autoindex/0,,147398,00.html) transfers data fromthe server to the client as live vector data ratherthan raster format data. Because of this, the clientcan perform functions such as quer ying,buffering, and thematic mapping withoutgenerating a large amount of network traffic.Autodesk MapGuide runs as a service underWindows NT. The client—Autodesk MapGuideViewer—uses Netscape API, ISAPI, and standardCGI interfaces to integrate with Netscape,Microsoft, and other web server products.

MapInfoMapInfo (http://www.mapxtreme.com/) has twoapplications that are basic variations of the originalMapXtreme.■ MapXtreme NT and MapXtreme Java Edition

are image-based applications that functionaround MapInfo’s MapX. In the MapXtreme JavaEdition, a client-side Java Bean provides the GISfunctionalities required for vector-basedapplications. Unlike MapXtreme NT, MapXtreme


Java Edition runs only on platforms that have aJava Virtual Machine. MapInfo’s web site forMapXtreme at http://www.mapxtreme.com/software/mapxtreme/nt_vs_java.html provides adetailed comparison of the two applications.

■ MapXsite (http://www.mapxtreme.com/mapxsite/index.html) is a stripped down versionof MapXtreme but provides several of thefunctions that many users and developers ofInternet-based GIS require. The tool allows users

to identify particular locations and to generatemaps locating various services and functions ofinterest to the user. The user can query morespecific information from this database. Thesefunctions, although basic to advanced users ofGIS applications, are a relatively easy to use,inexpensive, and quick way of launching a sitethat covers many of the basic needs of anorganization considering launching an Internet-based GIS site.


CHAPTER 5:SAMPLE IMPLEMENTATION OF ANINTERNET-BASED DECISION-SUPPORTTOOL

Once it has been decided to set up an Internet-baseddecision-support tool or to provide GIS functionsover the Internet, several issues need to be evaluatedbefore actually starting work on launching theInternet tool. Some technical and non-technical issuesinclude:

■ which GIS software, data, and model versions touse;

■ the site capacity and hardware/softwarerequirements to run the site;

■ the core team to be involved in implementingproject goals;

■ the programming languages to be used;■ which web browser (e.g., Netscape or Internet

Explorer) and which version to tailor theapplication to;

■ which target audience to tailor the web site to;■ the Internet access and speed of connectivity; and■ advertising and promoting the use and access to

the tool once it is functional.

An effective way to examine the issues and decisionsinvolved in making a GIS decision-support tool/Internet accessible is through a case study. To illustratesome of the challenges and issues involved in setting

up an Internet-accessible GIS tool, we describe thedevelopment of a particular site. The reader isencouraged to visit the site, use the tool, and assessthe degree to which the tool’s objectives have beenmet (http://www.ecn.purdue.edu/runoff).

The ToolThe Long-Term Hydrological Impact Assessment (L-THIA) model provides estimates of changes in runoff,recharge, and Non-Point Source (NPS) pollutioncaused by past, present, or future changes in land use.L-THIA was initially developed in response to a needfor a site suitability analysis tool for planners anddecision-makers that was easy to use and that madeuse of information readily available from municipaldatabases (Harbor 1994). L-THIA uses the CurveNumber (CN) approach to characterizing the impactthat different land uses and soils have on runoff, andcombines this with 30 years of local precipitation datato provide relative estimates of changes in long-termaverage runoff due to land use change. The L-THIAmodel was selected by the U.S. EnvironmentalProtection Agency (EPA Region 5) as a potentialInternet-accessible land use decision-support tool forplanners, municipalities, and other professionals andorganizations involved in making decisions that affect


land use change within watersheds. This model waschosen because it is easy to use, is nondata intensive,and is straightforward.

Originally, L-THIA was developed as a spreadsheetmodel (Harbor 1994). Although data requirementswere modest, they limited the use of L-THIA. Toovercome some of the data requirement difficultiesassociated with L-THIA, Grove (1997) integrated L-THIA with a GIS tool. The L-THIA model wasrewritten in the “C” programming language, and anexecutable program was created to run within the GISL-THIA system. After L-THIA was run, runoff depthand volume maps were created within the GIS.Although this system simplified its application, it wasstill difficult for many potential users. Bhaduri (1998)simplified and extended the system by creating a user-friendly interface within ArcView GIS and adding anNPS pollution estimation capability. Lim et al (1999)enhanced this version to consider additional NPSpollutants.

The goal of the project described below was to makeL-THIA available as a web-based decision-supporttool, both in its simple spreadsheet format and as aGIS tool.

The TeamAssembling a complete team covering all aspects ofdeveloping an Internet-based GIS is the first step increating a user-friendly tool. To make L-THIAInternet accessible, a team was assembled includingteam leaders, a model developer, and GIS andplanning professionals and programmers.

Team Leaders. Team leaders are needed to providelong-term vision for project direction and to co-ordinate efforts of the team. They were essential tokeep the project on track, as it is easy for individualteam members to lose perspective of overall projectgoals.

GIS Professionals. These professionals initiallyconverted the spreadsheet version of the model intoa GIS version and then extended these capabilities tothe Internet version. In the next stage, they workedwith GIS software programming to make the WWWversion of the model available as a download. Thisdownloadable version is to be used as an extensionwithin ArcView on the user’s local machines and thento extend similar capabilities without it beingnecessary for the client to have GIS software locallyor to have prior experience of GIS use.

Land Use Planners. Land use planners were includedin the team to ensure that information and tasks thatthe decision-support tool is designed to perform arealways aligned with the needs of the end user and sothat the information is explained and presented in amanner that to which the end user can relate.Additionally, the planner provided feedback to theprogrammers and ensured that the interface beingdeveloped for the decision-support tool was intuitive,especially for users without extensive GIS experience.

Programmers. Programmers were brought in tocover the technical aspects of serving the GISfunctions, data, the model, and the decision-supporttool over the Internet. The programmers wereresponsible for writing the CGI scripts, Java Script,Java programming, and providing the interfacebetween the server and the GIS software.

Serving the Tool Over the InternetProgramming issues: A variety of programminglanguages and approaches were used to create theWWW versions of L-THIA. The languages wereselected based on their capabilities and strengths. The“spreadsheet” version of the model was created usingHTML, Perl script, Java Script, and Java. Java Scriptand HTML were used to create the user interface. Perlscript uses the information provided by the user toquery weather data from an Oracle database and torun an executable version of the L-THIA model.Results are presented in tables, bar charts, or pie


charts. The graphics are created with Java Script andJava. Care was taken to maintain compatibilitybetween Netscape and Internet Explorer with theWWW spreadsheet version of the model. Some JavaScript and Java code function differently in thesebrowsers. To reach the maximum audience, it wasdesirable that the WWW spreadsheet version of thetool work in both browsers.

The ArcView Internet Map Server tool was selectedas the starting point for creating a WWW GIS versionof the L-THIA tool due to its ability to be extendedand the availability of the existing ArcView L-THIAtool. ArcView IMS was extended using Java to createthe WWW GIS L-THIA tool. Java was used to createthe interface that the user interacts with and toprovide an interface between the user and theArcView GIS functionality required to run the GISL-THIA.

For both the WWW spreadsheet and WWW GISversions of L-THIA, a server-side approach was usedin creating the WWW tools. This was used as opposedto the client-side approach because significantinteraction with tools on the server was required. Inboth instances, the weather database is maintainedin Oracle on the server. In the case of the WWW GIStool, capabilities within the ArcView GIS are used. Byusing the server-side approach, these capabilities canbe readily provided to the tool users.

One particularly important issue that came up whenmaking the model available on the Internet was thevariable level of familiarity that prospective clientsmight have with GIS functionalities and with standardGIS software. Not all clients of the site were expectedto have access to digital spatial data and it was essentialto consider that some users might prefer a spreadsheetversion of the model. Therefore, to cater to a wideraudience, including some who might not have readilyavailable data in GIS format or may not becomfortable dealing with a GIS, three WWW-basedversions of L-THIA with NPS pollution capabilities

were developed. The first is a spreadsheet-like version,the second is a set of downloadable Avenue scriptsthat can be run within ArcView on the user’s desktopcomputer, and the third is a WWW-based GIS versionthat accesses databases stored at a centralizedlocation.

Spreadsheet Version. In the WWW spreadsheetversion of L-THIA (Figure 2), the user interacts witha WWW interface written with HTML, Java Script,and Java to select the location (state and county) ofthe site being analyzed and to provide informationabout the area of each land use and hydrological soilgroup combination within the area of interest. Thelocation data provided by the user are used within aCGI script written in Perl to query an Oracle databaseon the WWW server to obtain the long-term dailyprecipitation data needed within L-THIA. Thus, theuser only needs to select the location of interest. Theydo not need to prepare a rainfall data file and otherinput requirements. Long-term daily rainfall data forapproximately 500 locations within the continentalU.S. are currently stored within the L-THIA WWW-based systems. A CGI script determines the curvenumber values from the land use and hydrologicalsoil information provided by the user. Once the CGIscripts have generated the necessary information, L-THIA is run on the WWW server using the rainfalldata and curve number values as input. The L-THIA-generated runoff and NPS pollution output areprocessed with CGI scripts, Java Script, and Java toprovide WWW-based tabular and graphicalrepresentations of the model outputs.

In the L-THIA/NPS WWW interface (Figure 2),weather data for the appropriate weather station arequeried from the database and reformatted for the L-THIA run (Figure 3). The user provides the area ofeach land use and hydrological soil group for eachperiod of interest. Areas of land use and soilcombinations can be provided for one to three timeperiods. For example, a user may wish to analyze theeffects of historical and future land use changes. Areas


Figure 2. L-THIA/NPS WWW Overview

of unique land use and soil combinations can beprovided for a past time period, as they are at present,or as they might be at some time in the future.Hydrological soil group maps can be requested fromthe interface for each of the 48 states in the continentalU.S. These hydrological maps along with counties andmajor roads appear in a second WWW browserwindow. The user can interactively zoom to thelocation of interest and determine the appropriatehydrological soil group(s) to use in the analysis. TheArcView IMS was used to provide access to the soilmaps and supporting data. Once the user hasprovided the information required by L-THIA, theyselect the “Run L-THIA” (Figure 2) button to run themodel. L-THIA runs on the WWW server andgenerates a series of tables, bar charts, and pie chartsfor runoff and NPS pollution.

In the L-THIA/NPS WWW runoff output table, allof the information that the user provided in the inputinterface is listed in addition to calculated values forcurve number, runoff depth, and runoff volume foreach time period analyzed. Bar graphs provide runoffdepth, runoff volume, total volume, and averagerunoff depth information. Presentation of the results

in this form can often assist the user in quicklyunderstanding model results. Land use and runoffvolume for each time of interest are also provided inpie-chart form. Tabular and graphical output is alsoavailable for each of the 12 NPS pollutants considered.

GIS Version. The ArcView GIS version of L-THIAwas created using a series of Avenue scripts and anexecutable version of the L-THIA model (Bhaduri1998, Lim et al. 1999). This version (Figure 4) (Lim etal. 1999) was used as the starting point for theimplementation of the WWW-based L-THIA GISsystem. ArcView IMS and Java were used to make thecore functionality of this system WWW accessible(Figure5).

The user interacts with the Java-based interface intheir WWW browser that sends requests to ArcViewIMS through the WWW server. ArcView IMS parsesthe information and executes corresponding Avenuescripts in the L-THIA GIS on the server. Once L-THIA components are run, appropriate maps arepassed back to the user’s WWW browser. The GIS L-THIA, and supporting data are maintained and runon the WWW server. This has many advantages forthe user, but most importantly it means that the userdoes not need to have a GIS, L-THIA code, or data

Figure 3. L-THIA WWW Spreadsheet Version UserInterface


on his/her computer, as this is maintained on the hostserver.

The ArcView L-THIA GIS application can also bedownloaded from the L-THIA WWW site for uselocally. To use this version of L-THIA, the user needsArcView and ArcView Spatial Analyst on theircomputer. Documentation and sample data sets arealso available for download with the ArcView L-THIA/NPS GIS to aid the user in utilizing the tool.Once the L-THIA extension is loaded, a set of buttonsappears on the screen within ArcView that can be usedto run L-THIA within ArcView (Figure 5).

To run the WWW-based L-THIA GIS version, theuser simply needs to have a WWW browser on theircomputer. The GIS and model components run onthe WWW server. The WWW interface (Figure 6)provides buttons to zoom and identify features withinthe maps presented in the user’s WWW browser. Theuser can also zoom to a location of interest byselecting pull-down menus with county names foreach state. The user can zoom in and digitize an area

of interest for an L-THIA model run. The L-THIApull-down menu enables users to run the L-THIAmodel. The runoff depth function creates a curvenumber map and runoff depth map using the landuse and hydrological soil group data for the areaidentified by the user. Runoff volume and NPSpollution maps are generated with the other menuselections.

L-THIA is designed for a wide range of users, fromland use planners to concerned citizens. The WWW-based L-THIA GIS version has an intuitive GUI. It

Figure 4. Serving L-THIA/NPS WWW GIS Version

Figure 5. ArcView Interface of the L-THIA/NPSGIS

Figure 6. L-THIA WWW GIS Showing Land Use forTippecanoe County, Indiana


provides simple, easy-to-use access to the model andfeatures drop-down menus for location, land use, andsoil type.

Some prior experience with ArcView is helpful inusing the ArcView L-THIA version. Introductorymaterial available at the web site can assist the usersin getting started with using the model. Detailed casestudies and tutorials for both versions are availableon the L-THIA homepage. Write-ups describing howto analyze model results aid users of the web-based

tool to evaluate results and the relative impacts ofdifferent land use changes within watersheds. The userhas the option of forwarding requests and questionsto the developers for detailed answers. This helpsmake the site more attractive to users and integratesthe model with the uses that the target audience islikely to make of the model.

The ArcView-based L-THIA tool is available at http://www.ecn.purdue.edu/runoff.


CHAPTER 6:MAPPING AND USER INTERFACE ISSUESINVOLVED

Developing a user-friendly interface that is intuitivefor the end user to obtain information from and usein the manner that the tool was intended requiresattention to several factors. In the case of the WWW-based L-THIA GIS tool, the team developed an initialversion of the tool. This was then presented to a widevariety of test users ranging from students,professional planners, environmental scientists, andaudiences at conferences. The feedback from suchinteractions was used to improve the site and make itmore user friendly. A series of supporting documentsin the form of background information and walk-through examples of using the tool were developedto assist the user in simulating L-THIA results.

Although using the Internet and spatial informationin the form of maps is intuitive for many persons, thecombination of using spatial information andaccessing GIS functions through the Internet isinitially daunting to most potential users. PresentingGIS functions and capabilities to users who havenever previously been faced with such information isa particularly challenging task.

Simply reproducing the interface of a traditionaldesktop GIS within an Internet browser is the easiest

approach and appeals to users already familiar withGIS, but does not necessarily work well for the generalpublic. The majority of the clientele of an Internet-based GIS or decision-support tool do not have priorexperience using such software. This makes the taskof serving such functions very different. A decisionto use the site is based on the usefulness of the tooland the ease with which the user can work out how touse the site. Thus, Internet GIS has several newchallenges compared to traditional GIS software,including a lack of prior experience in the users, spaceand time constraints, and to some extent differentrequirements for visual appeal. Good designers takethese concerns into account when designing userinterfaces for the Internet (Lowe 1999).

The GIS novice using the Internet may not be familiarwith GIS terms and capabilities. Techniques such asmap overlay, buffer analysis, and geocoding need tobe simplified and presented in a user-friendlygraphical interface (Figure 7).

Users without formal GIS training who access sitesproviding GIS functions for the first time must be ableto easily identify functions and capabilities and tomanipulate the spatial data with ease. The clients whoare expected to use the web-based tool are the most


Figure 7. Popular Website Used for a Variety ofGIS-Based Decision-Making

important factor to be considered when designing aGUI. Decisions such as the familiarity of the likelyaudience to GIS terminology such as pan, scale, co-ordinates, layer, rectification, or digital terrain model(DTM) are factors in deciding whether to use iconsinstead of these technical terms. In the case of WWW-based L-THIA/NPS GIS, icons were used to provideGIS functions such as zoom in, zoom out, pan, andgo back to the original data layer and the last displayedlayer (Figures 8 and 9).

New users often face a steep learning curve when firstusing spatial data. Analysis techniques common inGIS are significantly different from other types ofanalysis. Users need to familiarize themselves with thecommand structure and nomenclature of GIS. Whena user accesses an Internet-based GIS, knowledge ofdata coverage, structure and support systems shouldnot be required. This does not help in attracting newusers to web sites that have not looked after and solvedsuch issues.

To assist users in effectively obtaining results from thedecision-support tool, links are provided to

background-related information on using the tool;additionally, case studies have been developed andpresented as a series of worked-out examples. Thishas been further modified based on responsesreceived from users. Giving the user the option ofcontacting the team that developed the decision-support tool is mutually beneficial. It presents the userwith an opportunity to clarify any questions, doubts,or issues, and it provides the developers withbeneficial feedback and a view of user requirements.

Web sites that make use of intuitive symbols instead oftext to explain GIS functions such as overlay, buffer,pan, and zoom will attract users from a wider section.The EPA has large amounts of spatial data available onits web site (http://www.epa.gov). Users can query thelocation of environmental interest such as hazardouswaste sites, toxic release sites, and superfund sites bysimply clicking layers on and off (Figure 9). Users canalso locate schools, hospitals, churches, and otherfacilities by zooming into areas of interest.

User feedback is essential in designing andmaintaining a good site. Providing the user with theopportunity to offer feedback helps keep the siteattractive and easy to use. Interactive sites aregenerally perceived to be more attractive (Figure 7).The speed of performance is also valued highly byusers of web-based GIS tools (Doyle et al 1998).

Figure 8. Information to Assist Users


A well-designed web site anticipates errors likely tobe made by users, realizes the time it takes to loadparticular pages, and designs the GUI accordingly.Care needs to be taken regarding the size of displays.Most programmers and GIS professionals who aredesigning the site work use high-end computers withexceptionally large screens and, therefore, design theGUI accordingly. Most users, particularly for toolsthat are targeted to home audiences and smallorganizations, do not have similar facilities at homeand scrolling left and right and up and down is notalways the most convenient proposition.

Figure 9. EPA’s Website Serving Spatial Data(http://www.epa.gov)


CHAPTER 7:CONCLUSIONS

Making decision-support tool and GIS capabilitiesInternet accessible has many advantages for theproviders and the users of such facilities. Theseinclude financial savings for the user and provider,ease of access and learning, and ease of access toinformation; this encourages participation in theprocess, creating a more democratic process ofdecision-making. The advantages of sharedknowledge and data have been extensively discussedand their merits well established. The growth in thisindustry has been phenomenal in the last decade andwith more applications being developed in this andrelated fields there will likely be a phenomenal growthin its use in everyday life by persons who might notalready be using Internet-based GIS and decision-support tools.

This Quick Study outlines some of the advantages andthe issues involved in developing and implementingan Internet-based spreadsheet and GIS decision-support tool. However, there are rapid increases intechnology and growth in this field and this must bekept in mind when designing and implementing GISand decision-support tools that are Internet-based.Each tool is unique in the manner in which it can beimplemented and made operational. Issues such as

design of user interface and making the tool intuitiveto use and as user friendly as possible are generalrequirements and are not likely to change significantlywith changing technology and facilities available toserve such tools.

LIST OF FIGURES

Figure 1: Client-Server architecture for a web-basedGIS.

Figure 3. L-THIA/NPS WWW overview.Figure 2. L-THIA/NPS WWW spreadsheet version

user interface.Figure 5. Serving L-THIA/NPS WWW GIS Version.Figure 4. ArcView Interface of the L-THIA/NPS GIS.Figure 6. L-THIA WWW GIS Showing Land Use for

Tippecanoe County, Indiana.Figure 7. Popular web site used for a variety of GIS-

based decision-making.Figure 8: Information to assist users.Figure 9: EPA’s web site serving spatial data (http://

www.epa.gov/).


Shilpam Pandey has a Master of Science in UrbanPlanning and Management and specializes inGeographic Information System and Remote Sensingapplications. She is presently working at PurdueUniversity on various projects and is a team memberin the project to develop an Internet based DecisionSupport Tool for the Environmental ProtectionAgency (E.P.A.) Region 5.

Bernard Engel is a Professor in Agricultural andBiological Engineering at Purdue University. Hisresearch and teaching involves work in the field ofGeographic Information Systems (GIS), Internetbased Decision Support Tools, expert systems andneural networks applied to hydrologic/water qualityissues.

Jon Harbor is an Associate Professor ofEnvironmental Geosciences in the Department ofEarth and Atmospheric Sciences at Purdue University.His research interests range from glacial landformsand processes to the solution of practicalenvironmental problems. He is particularly interestedin ways to assess and manage the hydrologic andgeomorphic impacts of urban development, and wasthe originator of the Long-Term Hydrologic ImpactAssessment (L-THIA) model described in this book.

ABOUT THE AUTHORS


This section is provided to the user as a quickreference for words found in the field of Internettechnology and Geographic Information Systems.

ActiveX was developed by Microsoft; it allows usersto interact with remote computer hard drives and files.Netscape does not support ActiveX at this point andit can be turned off in Microsoft Internet Explorer.

Applet is a small downloadable Java application thatruns within a web page and creates special effects.

Bandwidth is the amount of information transferredwithin a specified period and is dependent on thespeed of the modem or Internet connection.

Browser is an application that allows users to use theInternet. The most popularly used browsers areNetscape and Microsoft Internet Explorer.

CGI (Common Gateway Interface) is a World WideWeb programming script that facilitates theinteraction between web browsers, servers, and otherdata and applications such as GIS software.

TABLE OF INTERNET GIS TERMINOLOGY

CORBA (Common Object Request BrokerArchitecture) allows programs at different locationsand developed by different vendors to communicatein a network through an interface broker. CORBAserves as an interface between the client and thebackground application much like CGI.

DGI (Distributed Geographic Information) asproposed by Plewe (1997) refers to the widespreaddistribution of geographic information to a largeraudience than those who have access to traditionaldesktop GIS.

DNS (Domain Name Server or Service) is an Internetservice that translates the names of computers andthe Internet names of businesses and organizationsto the Internet Protocol (IP) number that the Internetuses to actually identify each computer.

Domain name is a unique name of a particularInternet site (e.g., www.purdue.edu)

Firewall is a security measure taken by companies tokeep out any unwanted intruders. It protects theresources of a private network from users from othernetworks.


FTP (File Transfer Protocol) is one of the applicationsthat run on the Internet. This allows the user to uploadand download files from one computer to another.

Gopher is a menu-oriented hierarchical way oforganizing and retrieving information, madesomewhat obsolete by the World Wide Web. Gopherclient software, graphical or text-based, is used tonavigate up, down, and across local and globalresource lists.

GUI (Graphical User Interface) refers to a softwarefront-end meant to provide an attractive and easy-to-use interface between a computer user andapplication.

HTML (Hyper Text Markup Language) is a formatthat tells a computer how to display a particular webpage. The documents themselves are plain text files(ASCII) with special “tags” or codes that a webbrowser knows how to interpret and display on thescreen. It consists of tagged text, which is displayed tothe reader. The tags to the text tell the browser how toformat the text and provides information regardingpage layout, graphics, text fonts, text/backgroundcolor, and hypertext links.

http (Hyper Text Transfer Protocol) is a protocol formoving hypertext (typically web pages anddocuments) over the Internet.

hypertext is text that contains “links” to otherdocuments - words or phrases in the document thatcan be chosen by a reader and which cause anotherdocument to be retrieved and displayed.

Internet is a world-wide collection of computers,networks, and client computers, linked byTransmission Control Protocol/Internet Protocol andassociated protocols.

Intranet is an organizational network connectinginternal users with internal network, computing, anddata resources.

IP (Internet Protocol) is the “language” thatcomputers connected to the Internet use tocommunicate with each other.

IP Number is a 32-bit number used to uniquelyidentify every computer connected to the Internet.Usually expressed as four groups of numbers, eachranging from 0 to 255 (e.g., 208.4.210.2).

Java is an object-oriented, popularly used,programming language developed by SunMicrosystems. It is platform-independent and can runon UNIX, Windows, or Macintosh; it provides acommon interface for all computer platforms.

Java Script was developed by Netscape to providescripting on web pages. Where a Java applet iscompiled, the browser interprets the Java Script at thetime of download. Browsers that understand JavaScript will perform various dynamic changes to theweb pages. Many web sites now require Java- and JavaScript-enabled browsers.

Protocol is a specific method of communication or“language” that allows computers or softwareprograms to “talk” to each other to exchangeinformation or data.

Query is a request for information from a database.

SDTS (Spatial Data Transfer Standard) is a standardset by the U.S. government to promote and facilitatethe transfer of digital spatial data between dissimilarcomputer systems, while preserving informationmeaning and minimizing the need for informationexternal to the transfer.


Server is a computer that provides information toother computers on a network or the Internet (e.g., aweb server provides text as graphics files to webbrowsers running on client computers).

TCP (Transmission Control Protocol) is the majortransport protocol in the Internet suite of protocolsproviding reliable, connection-oriented, full-duplexstreams.

TCP/IP (Transmission Control Protocol/InternetProtocol) is a fundamental protocol that carries allInternet traffic for protocols such as File TransferProtocol, Telnet, Gopher, and Web.

URL (Uniform Resource Locator) is the addressingsystem used in the World Wide Web and otherInternet resources. The URL contains informationregarding the method of access, the server to beaccessed, and the path of any file to be accessed (e.g.,http://www.ecn.purdue.edu/~runoff is an URL).

VRML (Virtual Reality Modeling Language) is usedto serve three-dimensional information over theInternet using a VRML browser. In recent years, thepotential for visualizing urban spaces, elevationinformation, surface conditions, and other similarapplications has found widespread use in planningand community participation processes over theInternet.

Web Browser (World Wide Web browser), whichconnects over the Intranet or Internet to web servers,retrieves information in the form of home pages anddisplays (“render”) material according to imbeddedHTML tags.

Web Hosting is a set of services provided by acompany. The company provides space on theircomputers for businesses and individuals to put theirweb pages on. Many small companies do not need theexpense involved or have the extensive time necessaryto host their own web pages and use the servicesprovided by such a company.

Web Server is a program that accepts requests fromweb browsers and delivers (“serves up”) appropriatedocuments (“home pages”) and other files such asimages, video, and Java applets.

World Wide Web (WWW) is a networkingapplication that runs on the Internet. It is an easy butpowerful global information system, based on acombination of information retrieval and hypertexttechniques.


Autodesk http://www3.autodesk.com/adsk/autoindex/0,,147398,00.html

Bhaduri, B., 1998, A GIS-Based Model to Assess theLong-Term Impacts of Land Use Change onHydrology and Nonpoint Source Pollution. WestLafayette, IN: Purdue University, Department of Earthand Atmospheric Sciences. Thesis.

Craig, W.J., 1998, The Internet Aids CommunityParticipation in the Planning Process. Computers,Environment and Urban Systems, 22(4), 393-404.

Doyle, S., M. Dodge, and A. Smith, 1998, The Potentialof Web-Based Mapping and Virtual RealityTechnologies for Modeling Urban Environments.Computers, Environment and Urban Systems, SpecialIssue. Geocomputation 1998. 22(2), 137-155.

Environmental Systems Research Institute, Inc., http://www.esri.com/ http://www.esri.com/software/internetmaps/ims.html http://www.esri.com/software/arcview/extensions/imsext.html http://www.esri.com/software/mapobjects/ims/index.htmlhttp://www.esri.com/software/arcims/index.html

REFERENCES

Evans, A., R. Kingston, S. Carver, and I. Turton, Web-based GIS Used to Enhance Public DemocraticInvolvement. Centre for Computational Geography,School of Geography, University of Leeds, Leeds, WestYorkshire, LS2 9JT, Britain. Contact:[email protected], http://www.geog.leeds.ac.uk/research/papers/99-1/#wants

Grove, M., 1997, Development and Application of aGIS-Based Model For Assessing the Long-TermHydrological Impacts of Land Use Change. WestLafayette, IN: Purdue University, Department of Earthand Atmospheric Sciences. Thesis.

Harbor, J., 1994, A Practical Method for Estimatingthe Impact of Land-Use Change on Surface Runoff,Groundwater Recharge, and Wetland Hydrology.Journal of the American Planning Association, 60 (1),95-108.

Harder, C., 1998, Serving Maps on the Internet:Geographic Information on the World Wide Web. ESRIPress.


Intergraph Corporation. http://www.intergraph.com/dynamicdefault.asp,http://www.intergraph.com/software/geo_map/geo_web_4.asp http://www.intergraph.com/gis/

Lim, K.J., B. Engel, Y. Kim, B. Bhaduri, and J. Harbor,1999, Development of the Long Term HydrologicalImpact Assessment (L-THIA) WWW systems. PaperNo. 992009, ASAE, St. Joseph, MI.

Lowe, J.W., 1999, Looking Good On-line: Designingand Effective Website. GeoInfoSystems. October. 36-44

MapInfo (http://www.mapxtreme.com/http://www.mapinfo.com

McKee, L., 2000, Catch the Internet Wave. Open GISConsortium, Inc. OGIS Articles and Public Documents,http://www.opengis.org

Klein, D.H., 1999, The Internet and the Future of theDecision Making Process. URISA Annual ConferenceProceedings. Chicago, IL.

Plewe, B., 1997, GIS Online: Information Retrieval,Mapping and the Internet. Onword Press.

Pandey, S., R. Gunn, K.J. Lim, B. Engel, and J. Harbor,In Press, Developing a Web-Enabled Tool to AssessLong-Term Hydrological Impact of Land Use Change:Information Technologies Issues and a Case Study.

Peng, Z.R., 1999, An Assessment Framework for theDevelopment of Internet GIS. Environment andPlanning B: Planning and Design, 26, 11-132.

Smallworld http://www.smallworld.co.uk/products/core/swi/swi.asphttp://www.smallworld.co.uk/

Singh, R., 1999, Providing GIS Services over theInternet. URISA Annual Conference ProceedingsChicago, IL.

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