ISPRS, Vol.34, Part 2W2, "Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
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some distributed as plug-ins for many browsers (e.g. Adobe
SVG Viewer) and some available as stand alone viewers or
code libraries (SVG and X3D). The overall process of GML map
making is illustrated in Figure 1.
Figure 1. Process of GML Web Mapping
5. APPLICATION OF GML-BASED WEB MAPPING
Several Web Mapping products are available since 1997,
including Intergraph WebMap Server, ESRI Internet Map Server
(IMS), Autodesk MapGuide and others with lesser impact.
There are two primary data provision solutions in those products,
one is Java applets, and the other is browser plug-ins.
Java applets nice in principle, but slow in practice (still
optimistic), applets normally downloaded at beginning of each
site visit, plug-ins allow fast visualization and interaction, but
require initial download & installation.
Whether the client side of an Internet mapping solution is thin,
like a web browser, or thick, like a web enabled desktop product,
XML and its associated technologies can be used to transfer
geographic data. The size of the client will determine the
method used to display the map to the end-user, either via
Windows graphic calls, Java graphic calls, or possibly a plug-in.
We developed an ActiveX Control, called GMLViewer for
publishing GML data on the Web. Layers with map information
are converted from a GIS Products GeoBeans into GML files.
After it has download, GML data will be viewed by anyone on
the Web! The architecture of the sample GML application shows
in Figure 2.
Figure 2. Sample Architecture for GML Web Mapping
The Sample fragment of GML encoded file see as follows:
100,100 500,500
0
152.576,335.172
With GMLViewer, no Internet map servers are required in the
current version, the core of the GMLViewer are two parts, a
GML parser based on GML version 1.0 Profile 1 was developed
to parse GML file, which contains po¡nts^ lines and polygons and
mixed geometry element also. The GMLViewer makes use of
Microsoft XML parser to build up a Document Object Model
(DOM) tree from the received data. An ActiveX Control,
GeoBeans MapX Generator, is a component of GeoBeans
Software was used to render the DOM tree to get visualized
graphic element. GMLViewer also allows browser to view, zoom,
pan and select the map in client side and provides the functions
of getting attribute information from GML file. GML1.0 support
will be integrated totally in the new version of GeoBeans4.0. To
view the sample application, please visit our web site:
http://www.diQitalearth.net.cn/GeoBeans/GMLViewer.
6.CONCLUSIONS
The Web will be changed qualitatively, not only quantitatively
during the next few years. The new web will provide better tools
to manage not only page markup but also recognition and
organization of page content. The key to the future of IT is
communication, not PCs. The new web will be a semantic web,
