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The Development and Impact of Web-based Geographic Information Services Dr. Winnie S. M. Tang Managing Director, ESRI Hong Kong Limited., Level 10, Cyberport 2, 100 Cyberport Road, Hong Kong, Tel: (852) 27306883, Fax: (852) 27303772, E-mail: wtang@esrihk.com Jan Robert Selwood Project Manager, ESRI Hong Kong Limited., Tel./Fax: 81 5617 2 8887, E-mail: jrselwood@attglobal.net
Introduction
This year is the 10th anniversary of the first Web based Geographic Information Service. Xerox® Palo Alto Research Centre (PARC) launched the Map Viewer service in June 1993. Celebrations in June 2003 are likely to be muted as PARC has moved onto other research initiatives and the Map Viewer was discontinued in 1997 (PARC Company, 2002). Its legacy is however impressive, as can be seen by the explosion of web based mapping that has occurred since. It is notoriously difficult to gauge this ‘explosion’ by numbers of users. van Elzakker (2001:42) for example, makes reference to a survey in which 90% of respondents claimed to have used some form of web map; statistics provided by Media Metrix which indicated that map based weather and route finding sites appear within the top 40 most frequently accessed web sites in the US; and figures provided by MapQuest claiming production of 75.4 million maps for over 16.6 million user sessions in November 1999. These figures are now out-of-date. MapQuest alone claims 400 million maps requested by 60 million user sessions as its average monthly rate for 2002 (MapQuest, 2002); ESRI’s Geography Network shows peak traffic of up to 100,000 maps per hour (ESRI, 2002). These examples have been joined by an expanding list of public access web sites that provide map visualisation or spatial query/search functionality. Added to these are a host of specialist web servers providing dedicated mapping services to banking, tourist, routing, mobile telecommunications and utilities industries. Whilst the examples used by van Elzakker may be out-of-date they remind us of two important facts:
Evolution and Impacts of Geographic Web Services The PARC Map Viewer permitted zoom and pan functionality and enabled searching for predefined geographic locations. This introduced the concept of presenting geographic data on a web page in a format that can be interrogated; in other words in a format other than a static picture. The Internet or Intranet could be used to support web-based client access to, and interrogation of, centralized geographic information - this was of major significance for the GIS. From its inception GIS has struggling with a dilemma inherent within geographic data and analysis. On the one hand, geographic information and reasoning is deeply integrated with decision making at all levels – whether in connection with our daily lives, our businesses, administration and government, homeland security or emergency response. In addition, often the same data and the same services are used by widely differing organisations for widely differing purposes – the same street plan, or boundary outlines for example, are used by schools, the police, the local authorities, government and businesses alike. On the other hand, storage and analysis of geographic data is both complex and resource intensive. As a result, geographic or ‘spatial’ data has traditionally been very poorly integrated with other information delivery techniques - an observation applicable both to traditional hardcopy maps, but particularly so to computerised information systems. Not only has it been difficult to integrate GIS with other technologies, dissemination of GIS data and functionality has also been severely restricted as analytical complexity, the size and format of data sets involved and the limitations of network bandwidth have conspired to restrict GIS largely to a high end workstation application. Distributed access has been both limited and relatively expensive. GIS therefore, provided the tools to meet the widespread demand for geographic analysis in decision-making, but lacked a way of disseminating these. The Web changed this. It brought renewed focus on data standards, transfer formats, and an awareness of the benefits of open storage and development environments. Within GIS technology this change is apparent in the introduction of spatial objects to Object Relational Databases (such as ESRI’s ArcSDE and Oracle Spatial), and the move towards using open format data structures such as ESRI’s Shape file. It also led to the development of data transfer formats and applications designed specifically for delivery and interrogation of information across thin networks. The move away from proprietary development languages (e.g. MapBasic, MDL, AML) to standards such as COM and Java have also introduced an object oriented focus on encapsulation, componentisation and polymorphism which has seen very large complex applications (unwieldy and difficult to maintain, upgrade and integrate) being broken into lightweight, loosely coupled code. This permitted many geospatial services to be rendered as small applets and plug-ins that could operate across thin Internet or Intranet connections. Ultimately this lead to the increased sophistication of international standards such as Open GIS Consortium’s (OGC) Geographic Markup Language (GML) and other open variants of the Extensible Markup Language (XML) language such as ArcXML which facilitate transfer and exchange of intelligent geographic data between different applications. The significance of these developments is that they address the issues of dissemination and integration. Initially web-based GIS primarily permitted visualisation and simple query of spatial information, however increasingly; dedicated spatial web servers can perform complex spatial operations such as geocoding and route networking. Since the beginning of 2002 these are being provided as web services delivered in various forms of XML with their own Simple Object Access Protocol (SOAP) wrapping and Web Service Description Language (WSDL) descriptions, permitting complete integration of spatial functionality into other applications. Not only is web based GIS resolving problems with dissemination of geographic data and analyses – it is making these cheaper by dramatically altering the cost:benefit ratios of GIS implementation when assessed against user accessibility. This is shown schematically in Figure 1.  Figure 1: GIS Implementation Cost:User Ratio However, as Figure 1 shows, though overall cost of GIS ownership may have fallen, costs of data ownership remain significant. Such costs include collection or purchase of original data as well as data management and continued maintenance and update. To date, apart from permitting increased view access to datasets, web technology has had relatively little impact on the way data is actually managed. Future significant reductions in the cost of GIS implementation will need to come from addressing the collection, maintenance and management of data. The remainder of this paper considers two web-based initiatives that may go some way to addressing this: web data portals and web-based editing. |