center for advanced spatial information research,
University of Wisconsin-Milwaukee, usa
This paper introduces a proposed standard-based framework of Interoperable Internet GIS. This framework uses GML as a coding and data transporting mechanism to achieve data interoperability, WFS as a data query mechanism to access and retrieve data at the feature level on the Web, and SVG to display GML data on the Web as vector graphics. The combination of the three standard technologies would influence the development of Internet GIS
Internet GIS has been the most rapidly developing field in the geospatial technology industry. Many commercial Internet GIS programmes have been developed, such as: ESRI MapObject IMS and ArcIMS, AutoDesk MapGuide, Geomedia WebMap Server, and MapInfo MapXtreme, GE SmallWorld Internet Application Server and ER Mapper’s Image Web Server (Peng & Tsou, 2003).
Although these commercial Internet GIS programs greatly increase the accessibility of GIS data and tools, there are two problems associated with the current Internet GIS programs. First, current Internet GIS programs are not interoperable. This non-interoperability has two aspects. The first aspect is the data interoperability issue; the data created by different programs cannot be shared by others without data conversion. This causes problems for real-time data access, especially at the feature level (Peng, forthcoming). The second aspect is the access interoperability issue; data on the server can only be accessed by its own client. Other clients cannot access data due to proprietary access methods implemented by different Internet GIS programs. For example, a GeoMedia Web Map client cannot access data on the ArcIMS server. Enabling interoperability among heterogeneous systems and geospatial data is a challenging task for the development of Internet GIS, both technically and institutionally.
The second problem of current Internet GIS is that the graphic output of most commercial Internet GIS programs is in raster image formats such as GIF and JPEG. The graphic quality of raster images
Fig 1 Diagram of the Interoperable Future Internet GIS Framework (Peng, forthcoming)
Fig 2 Working process of case study (Peng and Zhang, forthcoming)
Fig 3 The Graphic User Interface of the GeoClient
is limited, and becomes blurred when zooming in. Delivering spatial data in a high-resolution vector format over the Web is becoming more important as data availability and global sharing increases (Bertolotto and Egenhofer, 2001). This paper discusses the role of Geography Markup Language (GML), the OpenGIS Web Feature Service (WFS), and Scalable Vector Graphics (SVG) in addressing these two issues faced by the development of future Internet GIS. A framework is proposed to use GML as a coding and data transporting mechanism to achieve data interoperability, WFS as a data query mechanism to access and retrieve data from the heterogeneous systems at the feature level to achieve access interoperability, and SVG to display GML data on the Web to improve the display quality of map graphics.
The purpose is to test the applicability and efficiency of integrating different standard-based technologies like GML, WFS, and SVG in promoting interoperability of Internet GIS programs and improving cartographic quality of Internet GIS visualization on the Web.